INTERNATIONAL ADVISORY COMMITTEE A. Carrington (Southampton, UK), Chair Emeritus J. M. Brown (Oxford, UK), Chair P. Casavecchia (Perugia, Italy) R. Colin (Brussels, Belgium) S. D. Colson (Richland, USA) R. F. Curl (Houston, USA) E. Hirota (Kanagawa, Japan) W. E. Jones (Halifax, Canada) M. Larsson (Stockholm, Sweden) S. Leach (Paris, France)

A. J. Merer (Vancouver, Canada) T. A. Miller (Columbus, USA) D. A. Ramsay (Ottawa, Canada) F. S. Rowland (Irvine, USA) T. C. Steimle (Tempe, USA) I. Tanaka (Tokyo, Japan) J. J. ter Meulen (Nijmegen, Netherlands) B. A. Thrush (Cambridge, UK)

LOCAL ORGANIZING COMMITTEE Yuan Tseh Lee (Honorary Chairman) Kopin Liu (Honorary Cochair) Yuan-Pern Lee (Chairman) Xueming Yang (Cochair)

Bor-Chen Chang Huan-Cheng Chang Kuo-Mei Chen Yit-Tsong Chen Bing-Ming Cheng Po-Yuan Cheng Su-Yu Chiang Eric Wei-Guang Diau Jia-Jen Ho Tong-Ing Ho

Sheng-Hsien Lin (Honorary Cochair) I-Chia Chen (Cochair)

Yen-Chu Hsu J.-M. Jim Lin King-Chuen Lin Wei-Tzou Luh J.-B. Nee Chi-Kung Ni Wen-Bih Tzeng Chin-hui Yu Niann-Shiah Wang

SYMPOSIUM VENUE The Grand Hotel 1, Sec. 4, Chung Shan N. Rd., Taipei 104, Taiwan TEL : 886-2-2886-8888 FAX : 886-2-2885-2885

SPONSORS National Science Council, Taiwan Academia Sinica, Taiwan Ministry of Education, Taiwan National Tsing Hua University, Taiwan

Content

List of Invited Lectures 1

List of Posters 3

Abstracts of Invited Lectures 13

Abstracts of Posters 45

Poster Session A: Monday Evening 47

Poster Session B: Tuesday Evening 85

Poster Session C: Wednesday afternoon 123

Index of Authors 161

1

List of Invited Lectures

No. Authors and Title pp.

M1 Suzuki, Toshinori Chemical Dynamics Studied by Time-Resolved Photoelectron Imaging

15

M2 Taylor, Mark; Muntean, Felician; McCoy, Anne; Barbera, Jack; Sanford, Todd; Rathbone, Jeff; Andrews, Django; Lineberger, W. Carl Time Resolved Solvent Rearrangement Dynamics

16

M3 Leone, Stephen R.; Müller, Astrid; Plenge, Jürgen; Haber, Louis; Clark, James Ultrafast X-Rays: Time-Resolved Photoelectron Processes in Molecular Dissociation

17

M4 Meijer, Gerard Manipulation of Molecules with Electric Fields

18

M5 Chou, Yung-Ching; Huang, Cheng-Liang; Ni, Chi-Kung; Kung, A. H.; Hougen, Jon T.; Chen, I-Chia Rotationally Resolved Spectra of Transitions Involving Motion of the Methyl Group of Acetaldehyde in the System à 1A" – X~ 1A'

19

M6 Chervenkov, S.; Georgiev, S.; Siglow, K.; Braun, J.; Chakraborty, T.; Wang, P.; Neusser, H. J. High Resolution Mass Selective UV Spectroscopy of Molecules and Clusters

20

M7 Choi, Jong-Ho Reaction Dynamics of Atomic Oxygen with Hydrocarbon Radicals

21

M8 Troya, Diego; Schatz, George C. Theoretical Studies of Reactions of Hyperthermal O(3P)

22

T1 Rowland, F. Sherwood Hydrocarbons in the Atmosphere

23

T2 Akimoto, Hajime Atmospheric Measurements of OH and HO2 Radicals in a Marine Boundary Layer

25

T3 Curl, Robert F.; Han, Jiaxiang; Hu, Shuiming; Brown, John; Chen, Hongbing; Thweatt, David Infrared Laser Spectroscopy and Chemical Kinetics of Free Radicals

26

T4 Zhu, R. S.; Xu, Z. F.; Lin, M. C. Ab Initio Studies of Free Radical Reactions of Interest to Atmospheric Chemistry

27

T5 Pollack, Ilana B.; Konen, Ian M.; Li, Eunice X. J.; Lester, Marsha I. Significant OH Radical Reactions in the Atmosphere: A New View

28

2

W1 Balaj, O. Petru; Balteanu, Iulia; Beyer, M. K.; Bondybey, Vladimir E.

Free Electrons: The Simplest Free Radicals of them All 29

W2 Merkt, Frédéric High-Resolution Photoelectron Spectroscopic Studies of Ions and Radicals

30

W3 Vilesov, Andrey F. Helium Droplets as a Unique Nano-Matrix for Molecules and Molecular Aggregates

31

W4 Bonhommeau, D.; Viel, A.; Halberstadt, N. Non-adiabatic Dynamics of Ionized Neon Clusters inside Helium Nanodroplets

32

W5 Momose, Takamasa Free Radicals in Quantum Crystals: A Study of Tunneling Chemical Reactions

33

R1 Zhou, Jingang; Shiu, W.; Zhang, B.; Lin, Jim J.; Liu, Kopin From Pair Correlation to Reactive Resonance in Polyatomic Reactions

34

R2 Skodje, Rex T. State-to-State-to-State Dynamics of Chemical Reactions: The Control of Detailed Collision Dynamics by Quantized Bottleneck States

35

R3 Brouard, Mark The Stereodynamics of Photon-Initiated Reactions

36

R4 Aoiz, F. J.; Bañares, L.; Barr, J.; Torres, I.; Pino, G. A.; Amaral, G. A. Photodissociation Dynamics of Polyatomic Molecules Containing Sulfur: An Experimental Study

37

R5 Ni, Chi-Kung Photodissociation of Simple Aromatic Molecules Studied by Multimass Ion Imaging Techniques

38

F1 Kerenskaya, Galina; Schnupf, Udo; Heaven, Michael C. Spectroscopy and Dynamics of NH Radical Complexes

39

F2 Hutson, Jeremy M.; Soldán, Pavel Molecules in Cold Atomic Gases: How do They Interact?

40

F3 Steimle, Timothy C. Optical Stark and Zeeman Spectroscopy of Transition Metal Containing Radicals

41

F4 Hsu, Yen-Chu The Bending Vibrational Levels of C3-Rare-Gas Atom Complexes and C2H2+

42

F5 Maier, John P. Electronic Spectra of Carbon Chains and their Relevance to Astrophysics

43

3

List of Posters Monday Evening, 26 July, 2004

No. Authors and Title pp.

A1-01 Laperle, Christopher M.; Mann, Jennifer E.; Continetti, Robert E. Three-Body Dissociation Dynamics of the Low-Lying Rydberg States of H3

47

A1-02 Lin, Jim J.; Perri, Mark J.; Van Wyngarden, Annalise L.; Boering, Kristie A.; Lee, Yuan T. Reaction Dynamics of Isotope Exchange Reaction of Singlet Oxygen Atom with Carbon Dioxide Molecule: A Crossed Molecular Beam Study

48

A1-03 Tseng, Chien-Ming; Dyakov, Yuri A.; Huang, Cheng-Liang; Mebel, Alexander M.; Lin, Sheng Hsien; Lee, Yuan T.; Ni, Chi-Kung Photoisomerization and Photodissociation of Aniline and 4-Methylpyridine

49

A1-04 Zhou, Weidong; Yuan, Yan; Zhang, Jingsong H-atom Elimination of n-Propyl and iso-Propyl Radicals: A Photodissociation Study

50

A1-05 Lee, Shih-Huang; Lee, Yuan T. Studies of Photodissociation Dynamics Using Selective Photoionization

51

A1-06 Zhang, Bailin; Shiu, Weicheng; Lin, Jim J.; Liu, Kopin Imaging the Mode-Correlation of Product Pairs: OH + CD4 → CD3 (000 Q, 202 Q) + HOD(ν1 ν2 0)

52

A1-07 Dyakov, Yuri A.; Mebel, Alexander M.; Lin, S. H.; Lee, Yuan T.; Ni, Chi-Kung Photodissociation of 4-Picoline, Aniline and Pyridine: Ab Initio and RRKM Study

53

A1-08 Lee, Yin-Yu; Dung, Tzan-Yi; Lee, Shih-Huang; Pan, Wan-Chun; Chen, I-Chia; Lin, Jr-Min; Yang, Xueming; Lee, Yuan T. Isomeric Species CH2SH and CH3S Formation from Photodissociation of Methanethiol at 157 nm

54

A1-09 Wu, Chia-Yan; Wu, Yu-Jong; Lee, Yuan-Pern Photodissociation of Fluorobenzene (C6H5F) at 193 nm Monitored with Time-resolved Fourier-transform Infrared Emission Spectroscopy

55

A1-10 Chen, Wei-Kan; Ho, Jr-Wei; Cheng, Po-Yuan Ultrafast Photodissociation Dynamics of Acetone S2 State at 195 nm

56

A1-11 Castillo, J. F.; Aoiz, F. J.; Banares, L.; Vazquez, S.; Martinez-Nuñéz, E.; Fernandez-Ramos, A. Quasiclassical Trajectory Studies of the F + CH4 Reaction Using an Ab Initio Potential Energy Surface Constructed by Interpolation

57

4

A1-12 Eskola, Arkke; Seetula, Jorma; Timonen, Raimo Kinetics of the Reactions of Methyl Radical with HCl and DCl at Temperatures 188 – 500 K: Tunneling

58

A1-13 Tseng, S. Y.; Huang, C. L.; Wang, T. Y.; Wang, N. S.; Xu, Z. F.; Lin, M. C. Kinetics of the NCN + NO Reaction

59

A1-14 Wu, Di; Wang, Bing-Qiang; Li, Zhi-Ru; Hao, Xi-Yun; Li, Ru-Jiao; Sun, Chia-Chung Single-electron Hydrogen Bonds in the Methyl Radical Complexes H3C⋅⋅⋅HF and H3C⋅⋅⋅HCCH: an ab initio Study

60

A1-15 Hela, P. G.; Shih, H.-T.; Cheng, C.-H.; Chen, I-C. Dynamics of Photoluminescence in Bistriphenylene

61

A1-16 Chang, Chih-Wei; Diau, Eric Wei-Guang; Chang, I-Jy Ultrafast Interfacial Electron Transfer Dynamics of the TiO2 Nanostructures Functionalized by the Ru2+ Complexes

62

A1-17 Hancock, G.; Morrison, M.; Saunders, M. Time Resolved FTIR Emission Studies of Molecular Dynamics

63

A2-01 Katoh, Kaoru; Sumiyoshi, Yoshihiro; Ueno, Taketoshi; Endo, Yasuki Fourier-Transform Microwave Spectroscopy of CCCl and CCCCCl

64

A2-02 Kobayashi, Kaori; Saito, Shuji Isotope Study of the CCO Radical in its 3Σ- Ground State by Microwave Spectroscopy

65

A2-03 Lin, Chia-Shih; Chang, Wei-Zhong; Hsu, Hui-Ju; Chang, Bor-Chen New Dispersed Fluorescence Spectra of Simple Halocarbenes in a Discharge Supersonic Free Jet Expansion

66

A2-04 Radi, Peter P.; Tulej, Marek; Knopp, Gregor; Beaud, Paul; Gerber, Thomas Double-Resonance Spectroscopy on HCO and H2CO by Two-Color Resonant Four-Wave Mixing

67

A2-05 Fink, E. H.; Ramsay, D. A. Near Infrared Emission Spectra of HO2 and DO2

68

A2-06 Evertsen, R.; Staicu, A.; van Oijen, J. A.; Dam, N. J.; de Goey, L. P. H.; ter Meulen, J. J. Cavity Ring Down Spectroscopy of CH, CH2, HCO and H2CO in a Premixed Flat Flame at both Atmospheric and Sub-atmospheric Pressure

69

A2-07 Yurchenko, Sergei N.; Carvajal, Miguel; Jensen, Per; Lin, Hai; Thiel, Walter Rotation-vibration Motion of Pyramidal XY3 Molecules Described in the Eckart Frame: Theory and Application to NH3

70

A2-08 Chen, Kuo-mei Resonance-enhanced Multiphoton Ionization Spectroscopy of CH3 and CD3. Two-photon Absorption Selection Rules and Rotational Line Strengths of the v3- and v4-Active Vibronic Transitions

71

5

A2-09 Shayesteh, Alireza; Appadoo, Dominique R. T.; Gordon, Iouli; Bernath, Peter F. The Vibration-Rotation Emission Spectra of Gaseous ZnH2 and ZnD2

72

A2-10 Balfour, Walter J.; Brown, John M.; Wallace, Lloyd Identification and Characterization of Two New Electronic Transitions of the FeH Radical in the Infrared

73

A2-11 Ashworth, Stephen H.; Varberg, Thomas D.; Hodges, Philip J.; Brown, John M. Detection of the Electronic Spectra of FeCl2 and CoCl2 in the Gas Phase

74

A2-12 Merer, A. J.; Peers, J. R. D.; Rixon, S. J. Free Radicals in the Reaction Products of Zr with Methane: the Electronic Spectra of ZrC and ZrCH

75

A2-13 Tang, Sheunn-Jiun; Chou, Yung-Ching; Lin, Jim Jer-Min; Hsu, Yen-Chu The Bending Vibrational Levels of Acetylene Cation: A Case Study of the Renner-Teller Effects with Two Degenerate Bending Vibrations

76

A2-14 Yoshida, K.; Kanamori, H. High Resolution Spectroscopic Studies of Vibrational States in the Triplet Potential of Acetylene

77

A2-15 Lin, I-Feng; Kurniawan, Fendi; Chiang, Su-Yu Experimental and Theoretical Studies on Rydberg States of H2CS in the Region 130-220 nm

78

A2-16 Jacox, Marilyn E.; Thompson, Warren E. Infrared Spectra of Neutral and Ionic SO2H2 Species Trapped in Solid Neon

79

A2-17 Jochnowitz, Evan B.; Zhang, Xu; Nimlos, Mark R.; Varne, Mychel Elizabeth; Stanton, John F.; Ellison, G. Barney Polarized IR Spectrum of Matrix-Isolated Propargyl Radicals and Detection of HC≡CH-CH2OO

80

A2-18 Cardenas, R.; Bates, S. A.; Robbins, D. L.; Rittby, C. M. L.; Graham, W. R. M. Recent Progress in FTIR and DFT Studies on the Vibrational Spectra and Structures of Group IV Clusters

81

A2-19 Delaney, Cailin; Clar, Justin; Cohen, Jodi; Abrash, Samuel A. Photochemistry of HI-Allene Complexes in Argon Matrices

82

A2-20 van de Meerakker, S. Y. T.; Vanhaecke, N.; Meijer, G. Decelerating OH and NH Radical Beams

83

A2-21 Hu, Shui-Ming; Liu, An-Wen; He, Sheng-Gui; Zheng, Jing-Jing; Lin, Hai; Zhu, Qing-Shi Inter-bonds Crossing Dipole Moment and Stretching Vibrational Bands Intersities of the Group V Hydrides

84

6

Tuesday Evening, 27 July, 2004

No. Authors and Title pp.

B1-01 Capozza, G.; Leonori, F.; Segoloni, E.; Balucani, N.; Stranges, D.; Volpi, G. G.; Casavecchia, P. Crossed Molecular Beam Studies of Radical-radical Reactions: O(3P) + C3H5 (Allyl)

85

B1-02 Balucani, N.; Capozza, G.; Segoloni, E.; Cartechini, L.; Bobbenkamp, R.; Casavecchia, P.; Bañares, L.; Aoiz, F. J.; Honvault, P.; Bussery-Honvault, B.; Launay, J.-M. The Dynamics of Prototype Insertion Reactions: Crossed Beam Experiments versus Quantum and Quasiclassical Trajectory Scattering Calculations on Ab Initio Potential Energy Surfaces for C(1D) + H2 and N(2D) + H2

86

B1-03 Lin, Ming-Fu; Dyakov, Yuri A.; Lin, Sheng-Hsien; Lee, Yuan T.; Ni, Chi-Kung Photodissociation Dynamics of Pyridine and C6HxF6-x (x = 1~4) at 193 nm

87

B1-04 Zhou, Weidong; Yuan, Yan; Zhang, Jingsong State-to-state Photodissociation Dynamics of OH Radical via the A2Σ+ State and Fine-structure Distributions of the O(3PJ) Product

88

B1-05 McCunn, L. R.; Miller, J. L.; Krisch, M. J.; Liu, Y.; Butler, L. J.; Shu, J. Molecular Beam Studies of the Photolysis of 2-Chloro-2-butene and the Subsequent Dissociation of the 2-Buten-2-yl Radical

89

B1-06 Shiu, Vincent W. C.; Lin, Jim J.; Liu, Kopin; Wu, Malcom; Parker, David H. Threshold is More Exciting: Seeing Reactive Resonance in a Polyatomic Reaction

90

B1-07 Martínez-Núñez, Emilio; Marques, Jorge M. C.; Vázquez, Saulo A. Dissociation of the Methanethiol Radical Cation Induced by Collisions with Ar Atoms: An Investigation by Quasiclassical Trajectories

91

B1-08 Obernhuber, Thorsten; Kensy, Uwe; Dick, Bernhard The Photodissociation Dynamics of t-Butylnitrite Initiated by Excitation to the S2 Electronic State

92

B1-09 Yang, Sheng-Kai; Chen, Hui-Fen; Liu, Suet-Yi; Wu, Chia-Yan; Lee, Yuan-Pern Photolysis of 2-Fluorotoluene at 193 nm: Internal Energy of HF Determined with Time-resolved Fourier-transform Infrared Emission Spectroscopy

93

B1-10 Cireasa, D. R.; Moise, A.; ter Meulen, J. J. Inelastic State-to-state Scattering of Oriented OH by HCl

94

B1-11 Castillo, J. F.; Aoiz, F. J.; Banares, L. Quasiclassical Trajectory Studies of the Cl + CH4 Reaction Using an Ab Initio Potential Energy Surface Constructed by Interpolation

95

7

B1-12 Pimentel, André S.; Nesbitt, Fred L.; Payne, Walter A.; Cody, Regina J. Planetary Chemistry of C2H5 Radicals: Rate Constant for the CH3 + C2H5 Reaction at Low Temperatures and Pressures

96

B1-13 Chou, Sheng-Lung; Lee, Yuan-Pern; Lin, Ming-Chang Experimental Studies of the Rate Coefficients of the Reaction O(3P) + CH3OH at High Temperatures

97

B1-14 Li, Zhi-Ru; Wu, Di; Li, Ru-Jiao; Hao, Xi-Yun; Wang, Bing-Qiang; Sun, Chia-Chung Electron Donor-Acceptor Bonds in the Methyl Radical Complexes H3C-BH3, H3C-AlH3 and H3C-BF3: an ab initio Study

98

B1-15 Liu, Kuan Lin; Cheng, Chao Han; Tang, Kuo-Chun; Chen, I-Chia Rapid Intersystem Crossing in Highly Phosphorescent Iridium Complexes

99

B1-16 Luo, Liyang; Chiang, Chia-Chen; Diau, Eric Wei-Guang; Lin, Ching-Yao Ultrafast Electron Transfer and Energy Transfer Dynamics of Porphyrin- TiO2 Nanostructures

100

B1-17 Yin, Hong-Ming; Sun, Ju-Long; Cong, Shu-Lin; Han, Ke-Li; He, Guo-Zhong The Internal Energy Distribution and Alignment Properties of the CH3O (X) Fragment by the Photodissociation of CH3ONO at 355 nm

101

B2-01 Suma, Kohsuke; Sumiyoshi, Yoshihiro; Endo, Yasuki Fourier-transform Microwave Spectroscopy and FTMW-millimeter-wave Double Resonance Spectroscopy of XOO (X = Cl, Br) Radicals

102

B2-02 Han, Huei-Lin; Chu, Li-Kang; Lee, Yuan-Pern Detection of Infrared Absorption of Gaseous ClCS Using Time-resolved Fourier-transform Spectroscopy

103

B2-03 Fan, Haiyan; Ionescu, Ionela; Annesley, Chris; Xin, Ju; Reid, Scott A. On the Renner-Teller Effect and Barriers to Linearity and Dissociation in HCF(Ã1 A")

104

B2-04 Colin, Reginald; Liu, Ching-Ping; Lee, Yuan-Pern Detection of Predissociated Levels of the SO B 3Σ- State using Degenerate Four-wave Mixing Spectroscopy

105

B2-05 Elliott, N. L.; Fitzpatrick, J. A. J.; Chekhlov, O. V.; Ashworth, S. H.; Western, C. M. Electronic Structure from High Resolution Spectroscopy

106

B2-06 Dagdigian, Paul J.; Nizamov, Boris; Teslja, Alexey Cavity Ring-Down Spectroscopy of Polyatomic Transient Intermediates: H2CN and H2CNH

107

B2-07 Pollack, Ilana B.; Konen, Ian M.; Li, Eunice X. J.; Lester, Marsha I. Significant OH Radical Reactions in the Atmosphere: A New View

108

8

B2-08 Muramoto, Yasuhiko; Ishikawa, Haruki; Mikami, Naohiko First Observation of the B~ (1A1) State of SiH2 and SiD2 Radicals by the OODR Spectroscopy

109

B2-09 Bernath, P.; Bauschlicher, C. W.; Dulick, M.; Ram, R. S.; Burrows, A. Metal Hydrides in Astronomy

110

B2-10 O'Brien, Leah C.; Hardimon, Sarah Fourier Transform Spectroscopy of Gold Oxide, AuO

111

B2-11 Balfour, Walter J.; Li, Runhua; Jensen, Roy H.; Shephard, Scott A.; Adam, Allan G. The First Observation of the Rhodium Monofluoride Molecule Jet-cooled Laser Spectroscopic Studies

112

B2-12 Miller, Terry A. Spectroscopy of Free Radicals in Hydrocarbon Oxidation

113

B2-13 Chou, Yung-Ching; Chen, I-Chia; Hougen, Jon T. Anomalous Splittings of Torsional Sublevels Induced by the Aldehyde Inversion Motion in the S1 State of Acetaldehyde

114

B2-14 Lee, P. C.; Yang, J. C.; Nee, J. B. Absorption Spectra of O2 and NO in 105-200 nm Wavelength Region Measured by using a Supersonic Jet

115

B2-15 Willitsch, Stefan; Innocenti, Fabrizio; Dyke, John M.; Merkt, Frédéric Rovibronic Energy Level Structure of the Two Lowest Electronic States of the Ozone Cation

116

B2-16 Lo, Wen-Jui; Chen, Hui-Fen; Chou, Po-Han; Lee, Yuan-Pern Isomers of OCS2: IR Absorption Spectra of OSCS in Solid Argon

117

B2-17 Zhang, Xu; Kato, Shuji; Bierbaum, Veronica M.; Ellison, G. Barney Gas-Phase Reactions of Organic Radicals and Diradicals with Ions

118

B2-18 Larsson, M.; McCall, B. J.; Huneycutt, A. J.; Saykally, R. J.; Geballe, T. R.; Djurić, N.; Dunn, G. H.; Semaniak, J.; Novotny, O.; Al-Khalili, A.; Ehlerding, A.; Hellberg, F.; Kalhouri, S.; Neau, A.; Paál, A.; Thomas, R.; Österdahl, F. H3+ Dissociative Recombination and the Cosmic-Ray Ionisation Rate towards ζ Persei

119

B2-19 Oguchi, T.; Hattori, T.; Matsui, H. The Reaction Mechanism of O(1D) with Ethylene: the Product Yield Measurements of OH, CH2CHO and H atom

120

B2-20 Geppert, W. D.; Thomas, R.; Ehlerding, A.; Hellberg, F.; Österdahl, F.; Millar, T. J.; Semaniak, J.; af Ugglas, M.; Djuric, N.; Larsson, M. Dissociative Recombination of Astrophysically Important Isoelectronic Ions

121

B2-21 Peterka, Darcy S.; Kim, Jeong Hyun; Wang, Chia C.; Ahmed, Musahid; Neumark, Daniel M. Photoelectron Spectroscopy of Nitric Oxide Doped in Helium Droplets

122

9

Wednesday Afternoon, 28 July, 2004

No. Authors and Title pp.

C1-01 Capozza, G.; Leonori, F.; Segoloni, E.; Volpi, G. G.; Casavecchia, P. Dynamics of HCCO and CH2 Radical Formation from the Reaction O(3P) + C2H2 in Crossed Beams using Soft Electron Impact Ionization for Product Detection

123

C1-02 Capozza, G.; Segoloni, E.; Volpi, G. G.; Casavecchia, P. Towards the "Universal" Product Detection in Crossed Beam Reactive Scattering Experiments using Soft Electron Impact Ionization: Dynamics of Vynoxy, Acetyl, Methyl, Formyl, and Methylene Radicals and Ketene Formation from the Reaction O(3P) + C2H4

124

C1-03 Liu, Chen-Lin; Hsu, Hsu Chen; Ni, Chi-Kung Photodissociation of I2+ Studied by Velocity Map Imaging

125

C1-04 Higashiyama, Tomohiko; Ishida, Masayuki; Honma, Kenji Dynamics of Reaction, Y(2D3/2, 5/2) + O2(X3Σ−g) → YO(A2Π) + O(3PJ), Studied by Crossed Beam-chemiluminescence Technique

126

C1-05 Miller, J. L.; McCunn, L. R.; Krisch, M. J.; Butler, L. J.; Shu, J. Molecular Beam Studies of the Dissociation and Isomerization of Radical Isomers: The Influence of the Electronic Wavefunction in the Dissociation Dynamics of Vinoxy Radicals

127

C1-06 Chang, Chushuan; Luo, Chu-Yung; Liu, Kopin Mode- and State-selected Photodissociation of OCS+ by Time-sliced Velocity Mapping Image Technique

128

C1-07 Martínez-Núñez, Emilio; Vázquez, Saulo A. Quasiclassical Trajectory Study of the 193 nm Photodissociation of CF2CHCl

129

C1-08 Fujimura, Yo; Tamada, Hisashi; Imai, Yoshiyuki; Mitsutani, Kazuya; Kajimoto, Okitsugu Reinvestigation of O(1D)+H2O Reaction: Examination of the Contribution of Excited States

130

C1-09 Bahou, Mohammed; Lee, Yuan-Pern Photodissociation Dynamics Investigated with a Pulsed Slit-jet and Time-resolved Fourier-transform Spectroscopy

131

C1-10 Lee, Sheng-Jui; Chen, I-Chia Ab Initio Studies for Dissociation Pathway and Isomerization of Crotonaldehyde

132

C1-11 Ho, Jr-Wei; Yang, Chia-Ming; Lai, Ta-Jen; Cheng, Po-Yuan The Use of Ultrafast Photodissociation as a Probe for Studies of Electronic Energy Transfer Dynamics

133

10

C1-12 Oum, Kawon; Sekiguchi, Kentaro; Luther, Klaus

The Role of Radical-Molecule Complexes in the Recombination Kinetics of Benzyl Radicals

134

C1-13 Alam, M. S.; Rao, B. S. M.; Janata, E. Reactions of •OH and H• with Aliphatic Alcohols: A Pulse Radiolysis Study

135

C1-14 Cheng, Mu-Jeng; Chu, San-Yan Substituent Effect on Structure and Bonding of Bertrand Diradical (X2P)2(BY)2

136

C1-15 Guss, Joseph; Kable, Scott Characterisation of the CCl2 Ã State

137

C1-16 Kumae, Takashi; Arakawa, Hatsuko Assessment of Training Effects on Levels of Serum Total Anti-oxidative Activity in Matured Rats using Luminol-dependent Chemiluminescence

138

C1-17 Dong, Feng; Whitney, Erin; Zolot, Alex; Deskevich, Mike; Nesbitt, David J. High Resolution Spectroscopy and Reaction Dynamics of Free Radicals

139

C2-01 Katoh, Kaoru; Sumiyoshi, Yoshihiro; Endo, Yasuki; Hirota, Eizi FTMW and FTMW-MMW Double Resonance Spectroscopy of the CH3OO Radical

140

C2-02 Juances-Marcos, Juan Carlos; Althorpe, Stuart C. Geometric Phase and the Hydrogen-Exchange Reaction

141

C2-03 Fan, Haiyan; Ionescu, Ionela; Annesley, Chris; Xin, Ju; Reid, Scott A. Polarization Quantum Beat Spectroscopy of HCF(Ã1A"): 19F and 1H Hyperfine Structure, Zeeman Effect, and Singlet-triplet Interactions

142

C2-04 Liu, Ching-Ping; Reid, Scott A.; Lee, Yuan-Pern Two-color Resonant Four-wave Mixing Spectroscopy of Highly Predissociated Levels in the à 2A1 State of CH3S

143

C2-05 Ahmed, K.; Balint-Kurti, G. G.; Western, C. M. Exploring the Potential Energy Surfaces of C3

144

C2-06 Zhang, Guiqiu; Chen, Kan-Sen; Merer, Anthony J.; Hsu, Yen-Chu; Chen, Wei-Jan; Sadasivan, Shaji; Liao, Yean-An; Kung, A. H. Perturbations in the à 1Πu, 000 Level of C3

145

C2-07 Marshall, Mark D.; Greenslade, Margaret E.; Davey, James B.; Lester, Marsha I. Partial Quenching of Orbital Angular Momentum in the OH-Acetylene Complex

146

C2-08 Fujii, Asuka; Miyazaki, Mitsuhiko; Ebata, Takayuki; Mikami, Naohiko Infrared Spectroscopy of Large-sized Protonated Water Cluster Cations: Development of the 3-Dimensional Hydrogen Bond Network with Cluster Size

147

C2-09 Luh, Wei-Tzou Electronically-excited Singlet States of LiH

148

C2-10 O'Brien, Leah C.; O'Brien, James J. Intracavity Laser Spectroscopy of NiH

149

11

C2-11 Jakubek, Zygmunt J.; Nakhate, Sanjay; Simard, Benoit; Zachwieja, Mirek Spectroscopy of Si+NH3 and Si-PH3 Reaction Products: Rovibronic Structure of the Ground Electronic States of SiNSi and PH2

150

C2-12 Varberg, Thomas D.; Le Roy, Robert J. Isotope Dependence and Born-Oppenheimer Breakdown in Mid- and Far-Infrared Spectra of Cadmium Hydride

151

C2-13 Baek, Dae Youl; Wang, Jinguo; Doi, Atsushi; Kasahara, Shunji; Baba, Masaaki; Katô, Hajime Doppler-free Two-photon Excitation Spectroscopy and the Zeeman Effect of the 1011401 Band of the S1 1B2u←S0 1A1g Transition of Benzene-d6

152

C2-14 Huang, Cheng-Liang; Liu, Chen-Lin; Ni, Chi-Kung; Hougen, Jon T. Electronic Spectra of Molecules with Two C3v Internal Rotors: Torsional Analysis of the A 1Au – X 1Ag LIF Spectrum of Biacetyl

153

C2-15 Willitsch, Stefan; Dyke, John M.; Merkt, Frédéric Rotationally Resolved Photoelectron Spectrum of NH2 and ND2: Rovibrational Energy Level Structure of the 1

1Aa~+ and 13BX~ + States

154

C2-16 Wu, Yu-Jong; Chou, Chun-Pang; Lee, Yuan-Pern Isomers of CNO2: Infrared Absorption of ONCO in Solid Neon

155

C2-17 Chou, Chun-Pang; Wu, Yu-Jong; Lee, Yuan-Pern IR Spectroscopy of Ge(NO) and Ge(NO)2 Isolated in Solid Argon

156

C2-18 Ehlerding, A.; Geppert, W.; Zhaunerchyk, V.; Hellberg, F.; Thomas, R.; Arnold, S. T.; Viggiano, A. A.; Semaniak, J.; Österdahl, F.; af Ugglas, M.; Larsson, M. Dissociative Recombination of Hydrocarbon Ions

157

C2-19 Thomas, R. D.; Ehlerding, A.; Geppert, W.; Hellberg, F.; Larsson, M.; Rosen, S.; Zhaunerchyk, V.; Bahati, E.; Bannister, M. E.; Vane, C. R.; Petrignani, A.; van der Zande, W. J.; Andersson, P.; Pettersson, J. B. C. The Effect of Bonding on the Fragmentation of Small Systems

158

C2-20 Hu, Qichi; Hepburn, John Dynamics and Spectroscopy of Threshold Photoion-Pair Formation

159

C2-21 Chen, Chun-Cing; Wu, Hsing-Chen; Tseng, Chien-Ming; Yang, Yi-Han; Chen, Yit-Tsong; One- and Two-photon Excitation Vibronic Spectra of 2-methylallyl Radical at 4.6-5.6 V

160

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13

Abstracts of Invited Lectures

14

15

Chemical Dynamics Studied by Time-Resolved Photoelectron Imaging

Toshinori Suzuki Chemical Dynamics Laboratory, Discovery Research Institute

RIKEN (Institute of Physical and Chemical Research) Wako, Saitama 351-0198, JAPAN

As the Born-Oppenheimer approximation indicates, chemical change is driven by

electrons. Observation of rapid changes of electronic state or electron configuration during the

course of chemical reaction will be essential for elucidating the dynamics. In the last decade,

solid-state ultrafast laser technology has been well established to allow various types of

pump-probe experiments of chemical reactions; however, further efforts seemed to be

necessary to directly observe electronic dynamics. We have combined femtosecond

pump-probe ionization method with two-dimensional imaging of photoelectron scattering

distribution to observe electronic dephasing processes in real-time. In addition to the

electronic dynamics, vibrational, and rotational wavepacket motions vary the kinetic energy

and ejection angle of photoelectrons, which makes time-resolved photoelectron imaging to be

a powerful tool for studying chemical dynamics. In this talk, we will present the method,

some recent results, problems, and future possibilities.

“Non-adiabatic dynamics effects in Chemistry revealed by time-resolved charged particle imaging”, T.

Suzuki and B.J. Whitaker, Int. Rev. Phys. Chem. 20, 313 (2001).

“Time-resolved photoelectron spectroscopy and imaging”, T. Suzuki in Modern Trends in Chemical

Reaction Dynamics, Advanced Series in Physical Chemistry, (World Scientific, 2004).

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Time Resolved Solvent Rearrangement Dynamics

Mark Taylor1, Felician Muntean1, Anne McCoy2, Jack Barbera, Todd Sanford, Jeff Rathbone, Django Andrews, and W. Carl Lineberger1

1JILA and Department of Chemistry and Biochemistry, Boulder, CO, USA 1JILA Visiting Fellow, 2003; Permanent Address, Ohio State University, Columbus, OH, USA

A femtosecond negative ion-neutral-positive ion charge reversal apparatus is

employed to investigate transient neutral species evolving along a reaction coordinate. We

report studies of the rearrangement dynamics of Cu(OH2) and Cu(OH2)2 produced by

photodetachment of the corresponding anion. Negative ion photoelectron imaging

spectroscopy is employed to characterize the initial anion. Following a controlled delay

period, a second ultrafast tunable laser pulse (photon energy close to that of the Cu 2P excited

state) initiates resonant multiphoton photoionization of the time-evolving Cu···OH2 complex.

The time-resolved Cu+ and Cu+(OH2) signals provide information both on the prompt

dissociation of the complex and on the slower (10s of ps) energy redistribution between

internal rotational and radial modes of the evolving complex. Calculations of the time

evolution of the anion geometric configuration on the neutral potential energy surface yield

deeper insight into the nature of the rearrangement process and the energy flow within the

complex. Recent studies on other partially solvated systems will be briefly discussed.

Supported by NSF and AFOSR

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Ultrafast X-Rays: Time-Resolved Photoelectron Processes in Molecular Dissociation

Stephen R. Leone, Astrid Müller, Jürgen Plenge, Louis Haber, and James Clark

Departments of Chemistry and Physics and Lawrence Berkeley National Laboratory University of California, Berkeley, CA 94720 USA

srl@cchem.berkeley.edu http://chem.berkeley.edu/people/faculty/leone/leone.html

Radical chemistry and production are investigated by ultrafast time-resolved photoelectron spectroscopy. High-order harmonics of a Ti:sapphire laser are produced in the vacuum ultraviolet or soft x-ray spectral region to serve as the probe pulses for valence shell and core level photoelectron spectra of transient and dissociating species. Soft x-ray femtosecond pulses are generated by focusing intense 800 nm pulses into a rare gas pulsed jet of Ar or Ne, producing the probe photons at every odd harmonic of 800 nm with energies up to 100 eV. Photofragmentation dynamics of small molecules is initiated with visible or ultraviolet pulses from the same master laser system. Two types of time-resolved photoelectron spectroscopies, x-ray photoelectron (XPS) and valence band photoelectron (PES), probe between different potential surfaces of the molecules. Diatomic molecules, such as bromine, are excited to a repulsive dissociative state or a bound electronic state, and selected harmonics are used to obtain time-resolved photoelectron spectra. The resulting bromine atom radicals are detected as they are produced in real time, and these signals are related to the timescale for the free atomic species to be formed. The wave packet amplitude on the dissociative state is observed and related to the above threshold ionization processes in the molecule, which occur simultaneously. Relative ionization cross sections are determined as a function of probe wavelength. New experiments emphasize dissociation and intramolecular processes in polyatomic molecule systems. Results are presented for the production and characterization of the harmonics, including spectral bandwidth determinations, temporal resolution, and the use of the harmonics for stable-molecule and dissociating-state core level and valence shell photoelectron spectroscopy. Related high resolution studies of molecules and radicals are performed at the Chemical Dynamics Beamline of the Advanced Light Source. A recirculating-linac-based concept for ultrafast x-ray pump-probe science is being developed, and the potential for studies with this possible future facility are also discussed.

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Manipulation of Molecules with Electric Fields

Gerard Meijer

Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany

and FOM Institute for Plasmaphysics Rijnhuizen,

Edisonbaan 14, NL-3439 MN Nieuwegein, The Netherlands During the last years we have been experimentally exploring the possibilities of manipulating neutral polar molecules with electric fields [1]. Arrays of time-varying, inhomogeneous electric fields have been used to reduce in a stepwise fashion the forward velocity of molecules in a beam. With this so-called 'Stark decelerator', the equivalent of a LINear ACcelerator (LINAC) for charged particles, one can transfer the high phase-space density that is present in the moving frame of a pulsed molecular beam to a reference frame at any desired velocity; molecular beams with a computer-controlled (calibrated) velocity and with a narrow velocity distribution, corresponding to sub-mK longitudinal temperatures, can be produced. These decelerated beams offer new possibilities for collision studies, for instance, and enable spectroscopic studies with an improved spectral resolution; first proof-of-principle high-resolution spectroscopic studies have been performed. These decelerated beams have also been used to load neutral ammonia molecules in an electrostatic trap at a density of (better than) 107 mol/cm3 and at temperatures of around 25 mK. In another experiment, a decelerated beam of ammonia molecules is injected in an electrostatic storage ring. The package of molecules in the ring can be observed for more than 50 distinct round trips, corresponding to 40 meter in circular orbit and almost 0.5 sec. storage time, sufficiently long for a first investigation of its transversal motion in the ring. A scaled up version of the Stark-decelerator and molecular beam machine has just become operational, and has been used to produce decelerated beams of ground-state OH and electronically excited (metastable) NH radicals. The NH radical is particularly interesting, as an optical pumping scheme enables the accumulation of decelerated bunches of slow NH molecules, either in a magnetic or in an optical trap. By miniaturizing the electrode geometries, high electric fields can be produced using only modest voltages. A micro-structured mirror for neutral molecules that can rapidly be switched on and off has been constructed and used to retro-reflect a beam of ammonia molecules with a forward velocity of about 30 m/s. This holds great promise for miniaturizing the whole decelerator, trap and storage ring for future applications.

References

[1] H.L. Bethlem and G. Meijer, Int. Rev. Phys. Chem. 22, 73 (2003)

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Rotationally Resolved Spectra of Transitions Involving Motion of the

Methyl Group of Acetaldehyde in the System A~ 1A″− X~ 1A′

Yung-Ching Chou,1 Cheng-Liang Huang,1 Chi-Kung Ni2, A. H. Kung2, Jon T. Hougen3, and

I-Chia Chen1 1Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan 30013, 2Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan 106

3Optical Technology Division, National Institute of Standards and Technology, Gaithersburg,

Maryland 20899-8441

Fluorescence excitation spectra, at resolution 0.02 cm-1, in the system A~ 1A″− X~ 1A′

were recorded for acetaldehyde in a supersonic jet. We performed full rotational analysis of

bands n000 1514

+ and n000 1514

− , for n = 0 – 5, in which 140+ and 140- denote the two inversion

tunneling components of the aldehyde hydrogen out of plane bending, in the vibrational

ground state of A~ 1A″. Torsional levels from the lowest energy to beyond the methyl

torsional barrier up to 370 cm-1 are assigned. These high energy states lying above the

torsional barrier display character between the limits of torsional vibrational motion and free

internal rotor motion, so that the close-lying 5A2 and 6A1 states mix for K > 0, and K states in

the E sublevel are widely split. Anomalous transitions (∆Ka = 0, ∆Kc = 0) to A sublevels are

observed for bands 4000 1514

+ and 3000 1514

− . The positions of A and E sublevels in 140-15n

cannot be fitted with a program involving only interaction of torsion and rotation,

furthermore for n = 0–1 states the A/E splitting is reversed from those in 140+15n.

Interaction with inversion evidently varies the splitting of torsional sublevels and the K

structure.

M5

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High Resolution Mass Selective UV Spectroscopy of Molecules and Clusters S. Chervenkov, S. Georgiev, K. Siglow, J. Braun, T. Chakraborty, P. Wang, and H. J. Neusser

Physikalische und Theoretische Chemie, Technische Universität München,

Lichtenbergstr. 4, D-85748 Garching, Germany Rotationally resolved UV spectra of molecular clusters in the gas phase have been measured with 100 MHz resolution and mass selection in a resonance-enhanced two-photon ionization process [1]. Analyzing the complex rotational structure of the vibronic bands of hydrogen-bonded clusters of aromatic molecules with water we have found information on the water position and the intermolecular vibrational dynamics. Results are presented for water complexes of benzonitrile, indole, and 4-fluorostyrene. Recently the technique has been successfully applied to flexible molecules of biological importance: the neurotransmitters ephedrine [2] and 2-phenylethanol. To better understand the conformational dynamics and the role of the intramolecular hydrogen bonds for the conformational stability we performed ab initio calculations. Combining pulsed high resolution and pulsed field ionization techniques we were able to resolve individual high Rydberg states (45 < n < 110) for the first time in a polyatomic molecule, benzene, and its van der Waals complexes with Ne, Ar, and Kr [1]. The series limits represent the individual rotational states of the respective radical cation yielding structural information on the van der Waals distance of the noble gas atom and on spin orbit coupling in the benzene radical cation induced by the external heavy noble gas atom.

Mass analyzed pulsed field threshold ionization (MATI) of bunches of very high Rydberg states is a powerful method for vibrational spectroscopy of radical cations and their production with defined internal energy. The mass selectivity allows us to detect with high precision the dissociation threshold of van der Waals bound aromatic radical cations with noble gases [3-5] and of hydrogen-bonded aromatic molecule-water complexes 3-methylindole-water and –benzene [6]. The ionization of the complex leads to strengthening of the hydrogen bond by factor of three caused by the additional charge.

[1] H. J. Neusser, K. Siglow, Chem. Rev. 100, 3921 (2000). [2] S. Chervenkov, P. Q. Wang, J. E. Braun, H. J. Neusser, submitted to J. Chem. Phys. [3] H. Krause, H. J. Neusser, J. Chem. Phys. 97, 5923 (1992). [4] J. E. Braun, H. J. Neusser, Mass Spectrom. Rev. 21, 16 (2002) [5] S. Georgiev, T. Chakraborty, H. J. Neusser, J. Phys. Chem. 108, 3304 (2004) [6] S. Georgiev, H. J. Neusser, Chem. Phys. Letters 189, 24 (2004)

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Reaction Dynamics of Atomic Oxygen with Hydrocarbon Radicals

Jong-Ho Choi

Department of Chemistry, Korea University, Seoul 136-701, Korea

The reaction dynamics of ground-state atomic oxygen (O(3P)) with propargyl (C3H3) radicals

have first been investigated by applying laser induced fluorescence (LIF) spectroscopy in a

crossed beam configuration. New exothermic channels (1) and (2) were observed, and the

nascent internal state distributions of some products showed substantial bimodal internal

excitations.

O(3P) + C3H3 → C3H2 + OH (1)

→ C3H2O + H (2)

We also performed ab initio, RRKM (Rice-Ramsperger-Kassel-Marcus) and prior

calculations to characterize the reaction mechanism and energy partitioning. It has been

found out that the surprising difference in the potential energy surfaces for the two reactions

plays a critical role in understanding the reaction mechanisms. We hope this work sheds

some light on the gas-phase atom-radical dynamics at the molecular level, which has been

very little explored so far.

[1] H.C. Kwon, J.H. Park, H. Lee, H.K. Kim, Y.S. Choi, and J.H. Choi*, J. Chem. Phys.

(Communications) 116. 2675 (2002).

[2] J.H. Park, H. Lee, H.C. Kwon, H.K. Kim, Y.S. Choi, and J.H. Choi*, J. Chem. Phys. 117.

2017 (2002).

[3] J.H. Park, H. Lee, Y.S. Choi, and J.H. Choi*, J. Chem. Phys. 119, 8966 (2003).[4]. H. Lee,

S.K. Joo, L.K. Kwon, J.H. Park, Y.S. Choi, and J.H. Choi*, J. Chem. Phys. (Communications)

119, 9337 (2003).[5] H. Lee, S.K. Joo, L.K. Kwon, and J.H. Choi*, J. Chem. Phys. 120, 2215

(2004).

[6] S.K. Joo, L.K. Kwon, H. Lee, and J.H. Choi*, J. Chem. Phys. 120, 7976 (2004).

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Theoretical Studies of Reactions of Hyperthermal O(3P)

Diego Troya and George C. Schatz

Department of Chemistry, Northwestern University, Evanston, IL 60208-3113 USA

Recently, Tim Minton at Montana State has performed a series of crossed molecular

beam experiments involving the reaction of hyperthermal oxygen atoms (several eV energies)

with H2, methane, ethane, propane and with polymer surfaces. These experiments are of

importance as they relate to the interaction of O(3P) found in low earth orbit with the

polymer-containing surfaces of space craft. This talk will describe a series of computational

simulations designed to model these reactions. The calculations are based on direct dynamics

calculations in which the MSINDO semiempirical electronic structure method is used to

determine forces for each time step in classical molecular dynamics simulations. For our

gas/surface simulations we also use QM/MM (quantum mechanics/molecular mechanics)

calculations in which the portions of the polymer that are close to the O atom are treated as

quantum atoms and the rest are described with molecular mechanics. We have calibrated the

quality of the MSINDO potential surface through extensive calibration with higher quality ab

initio calculations.

Although hydrogen abstraction to give OH plus an alkyl radical is the expected product

for O + alkane reactions, our hyperthermal results show that collision energies above 2 eV

lead to new reaction pathways, including addition of the O atom with H elimination to

produce alkoxy radicals, direct C-C bond breakage, direct water formation as well as aldehyde

formation. In certain cases we have been able to determine the importance of excited state

potential surfaces in the dynamics, as well as intersystem crossing effects. Collision induced

dissociation can play a role in some cases, and we have been able to show how angular

distributions for certain reactions switch from backward to forward peaked as collision energy

is increased.

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23

Hydrocarbons in the Atmosphere

F. Sherwood Rowland Departments of Chemistry and Earth System Science

University of California Irvine, California, 92697, U.S.A. The local presence of hydrocarbons in the atmosphere has been known for about two

centuries, with identification of specific compounds beginning about a century ago. However, the first confirmation that methane is present everywhere in the troposphere is generally attributed to Migeotte's spectroscopic measurements in 1948. Quantitative measurements of the simultaneous atmospheric presence of O3 and O2 demonstrate that the molar ratio is about 10-6, far in excess of a calculated thermodynamic equilibrium between them of 10-30. Similarly, the calculated thermodynamic equilibrium concentration of methane in the presence of O2 and H2O should be 10-140 times that of carbon dioxide. The atmosphere is thus far from equilibrium, in the former case because of the constant influx of solar radiation, and in the latter because many of the minor components such as methane are present in detectable amounts only because of ongoing emissions from biological sources. The reactive removal of volatile hydrocarbons from the atmosphere is primarily the consequence of attack by hydroxyl radicals, which are formed by ultraviolet attack on tropospheric ozone in (1) with the formation of O(1D) atoms which react with water vapor, as in (2). Hydroxyl radicals can attack saturated hydrocarbons by abstracting H in (3), and the residual R radical immediately adds an O2 molecule to form RO2 in (4). Hydroxyl radical formation is favored O3 + hυ → O(1D) + O2 (1) O(1D) + H2O → 2 HO (2) HO + RH → H2O + R (3) R + O2 → RO2 (4) in the summer because of more hours of more intense sunlight, and in the tropics by higher humidity which favors (3) in competition with deexcitation by collisions with N2 or O2.

The average atmospheric lifetime for a molecule I whose primary sink is reaction with HO can be approximately estimated from its measured laboratory reaction rate k3i versus k3 for a compound of known atmospheric lifetime. With a measured lifetime for anthropogenic methylchloroform, CH3CCl3, of five years, the alkanes have estimated lifetimes of 8 years for methane, 2 months for ethane, 2 weeks for propane, and a few hours for ethylene. Because the rate of north/south mixing of the atmosphere is approximately 15 months, methane is the only simple hydrocarbon which survives long enough to provide substantial contributions in both northern and southern hemispheres before being oxidized by HO radicals. For molecules such as ethane and propane, a strong seasonal variation is observed in the temperate and polar latitudes with minimum concentrations in the summer. Because most hydrocarbons enter the atmosphere in the north, the concentrations there are much very much higher than in the south.

We began collecting atmospheric samples in remote locations on both sides of the equator in 1978. Our measurements of methane in 1979 showed slightly higher concentrations than in 1978, indicating that its global concentration was rising. Continuation of this series of measurements have shown an increase from a global average of 1.52 ppmv in 1978 to 1.78 ppmv in 2003. Observations of methane from ice cores by other research groups show a gradual increase toward present levels from 0.75 ppmv at the beginning of the industrial revolution two centuries ago. The warming of the atmosphere by accumulation of

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anthropogenic gases was expanded in the 1970s from a "carbon dioxide problem" to a "greenhouse gas problem", with the experimental observation of significant increases over time of methane, nitrous oxide, the chlorofluorocarbons (CFCs), and tropospheric ozone as additional contributors to the trapping of outgoing infrared radiation. Water vapor is actually the major absorber of outgoing infrared radiation, but its atmospheric concentration responds to the temperature of the world's oceans, and increases as the Earth warms. With the assumption that all of the infrared radiation emitted by the Earth escapes to space, a simple calculation of the required average temperature for the Earth to emit enough infrared radiation to balance the incoming solar energy gives a temperature of −18°C. With an average Earth temperature of +14°C, this leads to a calculation of +32°C for the natural greenhouse effect. The calculation of a projected temperature increase of 1.4°C to 5.8 °C during the 21st century is the estimate of the incremental temperature increase which will accrue with the increases in global atmospheric concentrations of carbon dioxide, methane, nitrous oxide, CFCs, tropospheric ozone, water vapor and in various aerosols.

The RO2 radicals from (4) can react with NO in reaction (5) to form NO2, and its subsequent photolysis produces O atoms and then ozone. A very minor product of reaction (5) leads to the formation of alkyl nitrates, RONO2, which therefore become a marker for the production of ozone from the main channel of (5) + (6). We have investigated the hydrocarbon composition of the air RO2 + NO → RO + NO2 (5) NO2 + hυ → NO + O →→ O3 (6) in many cities around the world, and have observed not only the importance of vehicular traffic for the release of reactive hydrocarbons and nitrogen oxides, but also the importance of liquefied petroleum gas (typically C3 and C4 alkanes) in creation of urban ozone through reactions (4) to (6). We have also measured very high concentrations of alkane hydrocarbons in the rural southwest United States as the consequence of hydrocarbon leakage from the oil and gas industries. These alkanes have been accompanied by elevated alkyl nitrates, demonstrating that enough NO is present in these to trigger ozone formation even in these non-urban environments. We have also participated in numerous aircraft- and ship-based experiments which have led to other observations of hydrocarbons and their reactions. These include: (1) their formation by biomass burning, as measured both on the ground and in plumes

thousands of miles from the location of the burning; (2) removal by chlorine atom reaction in the near-absence of tropospheric ozone at altitudes

below 500 feet above frozen Hudson Bay (Canada); and (3) increased production of isoprene and alkanes accompanying CO2 decreases during "iron

fertilization" experiments in the Southern Ocean. All of these experiments have been performed in collaboration with Professor Donald R. Blake and various members of our research group, and with support from NASA and/or DOE, NSF, NASDA (Japan) and the Comer Foundation.

25

Atmospheric Measurements of OH and HO2 Radicals in a Marine Boundary Layer

Hajime Akimoto

Atmospheric Composition Research Program Frontier Research System for Global Change, Yokohama, Japan

akimoto@jamstec.go.jp The OH and HO2 radicals are the most important players of atmospheric reactions since

they are the key carriers of chain reactions of tropospheric photochemistry. Therefore, the

comparison between the observed and model-calculated concentrations of OH/HO2 radicals

can provide the most direct validation of tropospheric photochemical theory. Due to the very

low concentration of OH radicals (the order of 106 radicals/cm3 or less), however, reliable

measurement of these radicals has long been delayed since the pioneering attempt in 1970s.

Development of new technology enabled reliable measurement of these radicals on the

ground as well as in the aircraft since the middle of 1990’s. Since then three techniques has

been practically used in the ambient atmospheric application; laser-induced fluorescence(LIF),

differential optical absorption spectroscopy (DOAS), and chemical ionization mass

spectrometry (CIMS).

We developed a laser-induced fluorescence instrument and successfully implemented it in

field campaigns at three remote islands of Japan (Oki, Okinawa and Rishiri Island). At Cape

Hedo of Okinawa Island, the observed daytime level of HO2 agreed closely well with the

model-calculated results constraint to observed concentrations of NOx, hydrocarbonds,

aldehydes, CO, etc. which control “fast photochemistry” to generate and destroy HOx radicals.

This fact suggests that the photochemistry at Cape Hedo, Okinawa is well described by the

current mechanism.

In contrast, at Rishiri Island, the observed daytime concentration of HO2 was consistently

much lower than the model-calculated values in both 2000 and 2003 campaigns. Possible

processes that reduced the daytime HO2 are studied here, with the possibilities of (1)

heterogeneous loss of HO2 on aerosol surfaces, (2) unexpectedly fast HO2+RO2 reactions, and

(3) possible role of iodine chemistry. Analysis of simultaneous measurements of OH and HO2

radicals provides further discussion of unknown factors of atmospheric photochemistry.

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Infrared Laser Spectroscopy and Chemical Kinetics of Free Radicals

Robert F. Curl, Jiaxiang Han, Shuiming Hu, John Brown, Hongbing Chen, & David Thweatt Department of Chemistry, Rice Quantum Institute, Rice University, Houston, TX 77005

Our research has two aims: the observation and analysis of the infrared spectra of free

radicals and the investigation of their chemical kinetics. The degenerate CH stretching

fundamental of CH3O is our current interest. The upper state of the degenerate CH stretch

should consist of four subsystems corresponding to the four possible choices of the signs of l

and Σ relative to Λ. Significant progress has been made on this spectrum. Two sets of

subsystems have been observed in the jet-cooled spectrum and J values assigned to the lines

of their p-labeled component subbands. In addition, several apparently isolated subbands

have been assigned to p and J values. However, it is not clear at this time whether both of the

two assigned subsystems belong to the degenerate CH stretch even though they clearly have

perpendicular rotational selection rules. The spectra observed and our efforts to make sense of

them will be described. The infrared kinetic spectroscopy method is also used to explore

radical kinetics. A specific system of current interest is the determination of the product

yields of reactions of O(1D) with CH4. We have discovered significant hot atom effects even

at buffer gas (He) pressures above 10 Torr.

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Ab Initio Studies of Free Radical Reactions of Interest to Atmospheric Chemistry

R. S. Zhu, Z. F. Xu and M. C. Lin

Department of Chemistry, Emory University Atlanta, GA 30322, USA

Free radical reactions involving HOx, NOx, SOx and ClOx play their pivotal roles in

various aspects of atmospheric chemistry from acid rains to O3-formation in the troposphere

and O3-destruction in the stratosphere. Until recently prediction of their reaction rates and

product-branching ratios over a wide range of P,T-conditions had been difficult and unreliable.

Recent progress made in energy prediction by means of practically reliable computational

methods and rate constant calculations for barrierless radical-radical association processes by

solution of energy- and pressure-dependent master equation coupling all accessible quantum

states of multiple reactive intermediates allows us to estimate rate constants and

product-branching ratios to within kinetic accuracy. Several examples studied in our

laboratory on reactions of some of the aforementioned radicals will be discussed.

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Significant OH Radical Reactions in the Atmosphere: A New View

Ilana B. Pollack, Ian M. Konen, Eunice X. J. Li, and Marsha I. Lester Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6323 USA

The three-body OH + NO2 + M → HONO2 + M association reaction is of fundamental

importance in atmospheric chemistry because it is an important sink of reactive HOx and NOx

radicals that directly affect the ozone budgets of the troposphere and stratosphere. Until very

recently, HONO2 was believed to be the only product of the OH + NO2 reaction. However, a

surprisingly large discrepancy between OH kinetic loss measurements performed at high and

low pressures has lead several groups to suggest that peroxynitrous acid (HOONO), a less

stable isomer of HONO2, may be a secondary product of this reaction and the coupled HO2 +

NO reaction.

Recently, this laboratory produced HOONO by reaction of photolytically generated

OH and NO2 radicals, stabilized the intermediate in a pulsed supersonic expansion, and

identified the trans-perp (tp) conformer of HOONO through infrared action spectroscopy in

the OH overtone region.[1] Extensive rotational band structure associated with the OH

overtone transition yields structural parameters and its transition dipole moment, which are in

good accord with ab initio values. The infrared overtone excitation provides sufficient

energy to break the O-O bond of tp-HOONO, producing OH (v=0) fragments that are detected.

The internal energy distribution of the OH fragments is consistent with a prior distribution,

and enables an accurate determination of the HOONO binding energy. The

spectroscopically derived value is in good accord with recent theoretical results and a kinetic

estimate of its stability. Comparisons will be made with previous infrared studies of

HOONO conformers isolated in Ar matrices [2] and more recent studies in a discharge flow

tube.[3,4] Many issues concerning the formation, isomerization, dissociation, and yield of

HOONO under jet-cooled and atmospheric conditions will be discussed in the oral and poster

presentations.

[1] I. B. Pollack, I. M. Konen, E. X. J. Li, and M. I. Lester, J. Chem. Phys. 119, 9981 (2003). [2] B. M. Cheng, J. W. Lee, and Y. P. Lee, J. Phys. Chem. 95, 2814 (1991); W.-J. Lo and Y. P.

Lee, J. Chem. Phys. 101, 5494 (1994). [3] S. A. Nizkorodov and P. O. Wennberg, J. Phys. Chem. A 106, 855 (2002). [4] B. D. Bean, A. K. Mollner, S. Nizkorodov, G. Nair, M. Okumura, S. P. Sander, K. A.

Peterson, and J. S. Francisco, J. Phys. Chem. A 107, 6974 (2003).

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Free Electrons: The Simplest Free Radicals of them All

O. Petru Balaj1, Iulia Balteanu1, M. K. Beyer1 and Vladimir E. Bondybey1,2, 1Institute für Physicalishe Chemie, Technische Universität München, Garching

2Department of Chemistry, University of California, Irvine Free radicals are usually defined as highly reactive species with unpaired electrons. Electrons themselves are highly reactive and unpaired and can therefore be considered to be the simplest free radicals. In the almost two hundred years since Humphrey Davy first noted the blue color appearing when sodium is dissolved in ammonia, free electrons in solutions have been extensively studied. More recently it was shown, that solvated gas phase electrons1 can also be generated, and we have found that a laser vaporization source developed in our laboratory with supersonic expansion, produces very cleanly hydrated electron clusters e!(H2O)n with n − 12-100 for studies by Fourier Transform Ion Cyclotron Resonance (FT-ICR) Mass Spectrometry. Even in the absence of collisions the trapped clusters gradually disappear due to heating by the black body infrared background radiation, and interesting size dependent competition between the loss of ligands and electron detachment. The finite clusters with exactly known composition are a very convenient medium for electron reaction studies, since unlike bulk solution “pulsed electrolysis” experiments they are not plagued by the effects of minor impurities. We will discus and describe here briefly the rich, multifaceted chemistry of the electron clusters, whose reactions can be crudely classified into several categories: a) Many simple, nonpolar molecules and atoms just contribute to cluster fragmentation b) Polar molecules capable of forming strong, hydrogen bonded networks can be exchanged for the water ligands, and gradually replace part or even all of the aqueous shell c) Reactions with species such as O2 or CO2, which can attach the free electron forming an anion stabilized strongly by hydration, result in replacement of the ionic core of the cluster. d) With a number of species, for instance acetonitrile or HCl, a true “chemistry” is observed, where existing covalent bonds are broken and/or new ones formed. 1. M. Armbruster, H. Haberland, and H. G. Schindler, Phys. Rev. Lett. 47, 323 (1981) 2. M. K. Beyer, B. S. Fox, B. M. Reinhard and V. E. Bondybey, J. Chem. Phys. 115, 9288 (2001)

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High-Resolution Photoelectron Spectroscopic Studies of Ions and Radicals

Frédéric Merkt

ETH Zürich, Physical Chemistry, CH-8093 Zürich, Switzerland

Photoelectron spectroscopy (PES) represents a useful tool to study the photoionization

dynamics of molecules and to study the properties of molecular radicals and ions. In the past

years progress has been made that enables the recording of VUV PE spectra at high resolution

using several variants of the technique of pulsed-field-ionization zero-kinetic energy

(PFI-ZEKE) PES. In our experiments, we record such spectra by monitoring the field

ionization of very high Rydberg states (n > 150) located below each ionization threshold as a

function of the wavenumber of a narrow bandwidth VUV laser. In a first variant, carefully

designed electric field pulse sequences are used to achieve a high selectivity in the field

ionization process and to record PE spectra at a resolution of 0.06 cm-1 [1]. A second variant,

called Rydberg-state-resolved threshold ionization can be used to resolve the high Rydberg

states within each line in a PFI-ZEKE PE spectrum, enabling one to record photoelectron

spectra at a resolution limited by the bandwidth of the laser radiation used (in our case

250 MHz) [2]. Finally, millimeter wave spectroscopy can be used to record transitions

between high Rydberg states at sub MHZ resolution [3]. Our studies have enabled us to

resolve the complete rotational structure and in several cases the spin-rotational fine structure

and even the hyperfine structure in the PE spectra of molecules. A new source of cold radicals

in supersonic expansions has been developed that is compatible with the high-vacuum

requirement of our PFI-ZEKE PE spectrometers and which can be used to study a wide range

of radicals [4]. The talk will present a survey of these developments and illustrate them by PE

spectroscopic measurements carried out on hydride radicals such as NH2, CH2 and C2H5 and

on reactive molecules such as O3.

[1] U. Hollenstein, R. Seiler, H. Schmutz, M. Andrist, and F. Merkt, J. Chem. Phys. 114, 9840 (2001). [2] R. Seiler, U. Hollenstein, G. M. Greetham, and F. Merkt, Chem. Phys. Lett. 346, 201 (2001). [3] A. Osterwalder and F. Merkt, Int. Rev. Phys. Chem. 21, 385-403 (2002). [4] S. Willitsch, J.M. Dyke, and F. Merkt, Helv. Chim. Acta 86, 1152-1166 (2003).

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Helium Droplets as a Unique Nano-Matrix for Molecules and Molecular Aggregates

Andrey F. Vilesov

Department of Chemistry, University of Southern California, Los Angeles, CA 90089, USA

In this talk experiments on spectroscopy of molecules and molecular complexes in

helium droplets will be reviewed. Some recent developments include the introduction of

pulsed droplet beams and the application of pulsed infrared lasers to molecular spectroscopy

in droplets. The study of the phthalocyanine (Pc), Mg-Pc and Zn-Pc molecules in helium

droplets is reported. The electronic spectra in the vicinity of the band origins show low

energy vibronic bands. These bands correspond to vibrational modes of several helium

atoms localized by molecular interaction. In other experiments we used large helium

droplets of 105 – 107 atoms as hosts to assemble molecular clusters. The rotationally

resolved spectra of the ν1 and ν3 vibrational modes of (NH3)n clusters and the ν3 mode of

(CH4)n (n = 1 – 2x103) clusters in He droplets have been obtained. The quenching of the

molecular rotational motion and the development of the vibrational bands of molecular

clusters upon an increase in cluster size are studied.

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Non-adiabatic Dynamics of Ionized Neon Clusters inside Helium Nanodroplets

D. Bonhommeau, A. Viel, and N. Halberstadt

LPQ-IRSAMC, CNRS and University Paul Sabatier, 118 route de Narbonne, 31062 Toulouse, France

One of the most common experimental tools to study host molecules or clusters inside

helium nanodroplets is mass spectrometry, which implies an ionization step. This ionization

usually produces fragmentation of the host molecule or cluster. The purpose of this work is to

determine the role of the helium environment in the dissociation. Is there no effect since these

nanodroplets have been shown to be superfluid, or is any dissociation inhibited because of the

very high heat conductivity of superfluid helium? Ionized rare gas clusters constitute ideal

model systems to study these fragmentation processes. Ionization brings the cluster from the

neutral configuration with bond lengths typical of Van der Waals bonding to the ionic

surfaces where the equilibrium bond lengths are much shorter. The cluster ion is thus

produced in a configuration containing a large amount of internal energy and dissociates.

Experiments by Janda and coworkers [1] have shown that their fragmentation is significantly

hindered, and can even be caged, in helium nanodroplets.

We have set up a simulation [2] of the ionization-dissociation process of these rare gas

clusters in a helium nanodroplet, using the molecular dynamics with quantum transitions

(MDQT) method [3] to treat the inherently multi-surface nature of the dynamics. The

electronic part is evolved quantum-mechanically, while the coordinates of the atoms are

propagated classically, with hops between adiabatic surfaces allowed. The potential energy

surfaces are described in the diatomics in molecules (DIM) model. The helium environment is

described by an ad hoc model, using a friction force acting on atoms with velocities above the

Landau critical velocity. A reasonable range of values for the corresponding friction

coefficient is obtained by comparison with existing experimental measurements.

[1] B.E. Callicoatt, K. F¨orde, T. Ruchti, L. Jung, and K.C. Janda, J. Chem. Phys. 108,

9371 (1998). [2] D. Bonhommeau, A. Viel and N. Halberstadt, J. Chem. Phys., in press. [3] J.C. Tully, J. Chem. Phys. 93, 1061 (1990).

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Free Radicals in Quantum Crystals: A Study of Tunneling Chemical Reactions

Takamasa Momose

Division of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan e-mail: momose@kuchem.kyoto-u.ac.jp

Solid parahydrogen is a unique matrix for the study of chemical reactions of cold

molecules.[1,2] By virtue of the softness of solid parahydrogen as a quantum crystal,

rotational motion of molecules in the crystal is well quantized as in the gas phase. Moreover,

molecules are mobile in the crystal, so that various chemical reactions occur in the crystal.

As a result, quantitative information on chemical reactions of nearly free molecules at liquid

He temperatures such as tunneling chemical reactions can be obtained directly from the

spectroscopy of molecules in solid parahydrogen.

In the present work, tunneling chemical reactions between deuterated methyl

radicals and the hydrogen molecule in a parahydrogen crystal have been studied by FTIR

spectroscopy. The tunneling rates of the reactions R + H2 → RH + H (R=CD3, CD2H, CHD2,

and CH3) in the vibrational ground state were determined directly from the temporal change

in the intensity of the rovibrational absorption bands of the reactants and products in each

reaction in solid parahydrogen observed at 5 K. The tunneling rate of each reaction was

found to differ definitely depending upon the degree of deuteration in the methyl radicals.

The tunneling rates thus determined were 3.3 ×10-6 s-1, 2.0×10-6 s-1, and 1.0 ×10-6 s-1 for the

systems of CD3, CD2H, and CHD2, respectively. Conversely, the tunneling reaction between

a CH3 radical and the hydrogen molecule did not proceed within a week's time. The upper

limit of the tunneling rate of the reaction of the CH3 radical was estimated to be 8×10-8 s-1.

The tunneling reaction rates are clearly faster for heavier isotopomers in these systems. The

"anomalous" deuteration effect will be discussed. 1. T. Momose, and T. Shida, Bull. Chem. Soc. Jpn, 71, 1 (1998). 2. T. Momose, H. Hoshina, M. Fushitani, and H. Katsuki, Vib. Spectrosc. 34, 95 (2004). 3. T. Momose, H. Hoshina, N. Sogoshi, H. Katsuki, T. Wakabayashi, and T. Shida, J. Chem. Phys. 108, 7334 (1998). 4. H. Hoshina, M. Fushitani, T. Momose, and T. Shida, J. Chem. Phys. 120, 3706 (2004).

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From Pair Correlation to Reactive Resonance in Polyatomic Reactions

Jingang Zhou, W. Shiu, B. Zhang, Jim J. Lin, and Kopin Liu

Institute of Atomic and Molecular Sciences, Academia Sinica, P. O. Box 23-166, Taipei,

Taiwan 106

A novel time-sliced velocity imaging technique has been developed and implemented in

crossed-beam scattering experiments. Using this new approach, a number of atoms/radicals

with methane, such as F, Cl, OH + CH4 etc., and its isotopic variants were investigated. What

revealed from these studies is the coincident information of the state-resolved pair-correlation

of the two products. The correlated state distributions and differential cross sections show

striking differences for various product pairs, which open a new way to unravel the

complexity of a typical polyatomic reaction.

In this talk, we will elucidate the concept of product pair correlation and highlight some

of the major findings. In addition, we will show how such kind of measurements leads to the

discovery of a reactive resonance in six-atom reactions of F + CH4 and F + CHD3.

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State-to-State-to-State Dynamics of Chemical Reactions: The Control of Detailed Collision Dynamics by Quantized Bottleneck States * (i-iii)

Rex T. Skodje1,2

1) Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan

and 2) Department of Chemistry, University of Colorado

It has long been realized that the characteristics of the transition state of a chemical reaction

control the reaction rate constant. More recently, Truhlar and coworkers have established

that quantized bottleneck states (QBS), which lie at the maxima of adiabatic potential curves,

provide a basis to understand the energy dependence of the cumulative reaction probability.

In this presentation, we discuss new work that reveals that the control exerted by the QBS

extends even to highly detailed state-to-state differential cross sections of elementary

reactions. Using various isotopes of the H+H2 prototype reaction, we show how the

angular dependence and product distribution of the reactions can be rationalized in terms of

the properties of the QBS. The understanding of the (initial) state-to (transition) state-to

(final) state reaction dynamics not only provides a basis to observe the QBS, but also adds

predictive power to the study of reaction dynamics.

* This work was done in collaboration with SD Chao, M. Gustafsson, and the experimental group of XM Yang. i) S. A. Harich et al, Nature, 419, 281 (2002). ii) D. X. Dai, et al, Science, 300, 1730 (2003). iii) S. A. Harich, et al, J. Chem. Phys., 117, 8341 (2002).

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The Stereodynamics of Photon-Initiated Reactions

Mark Brouard*

The Physical and Theoretical Chemistry Laboratory,

Department of Chemistry, University of Oxford,

South Parks Road, Oxford OX1 3QZ, United Kingdom

Laser pump-probe techniques have been used to study the stereodynamics of photon initiated unimolecular and bimolecular processes. The experiments employ polarized photolysis radiation coupled with either laser-induced fluorescence (LIF) or resonantly enhanced multiphoton ionisation (REMPI) and velocity-map ion-imaging. Using the latter technique, we have recently characterized the O(3PJ) photofragments generated in the photodissociation of N2O at 193nm: N2O + hv N2 + O(3PJ) The dependence of the ion-images, and integrated image intensities, on laser pump-probe polarization geometry has enabled us to determine the electronic alignment of the ground state O-atom photofragments [1]. The data have been used to help identify the electronic channel responsible for spin-forbidden dissociation in this atmospherically important molecular system.

Our studies of bimolecular processes are of the photon-initiated type [2], as illustrated by the example HX + hv H + X H + H2O OH(2ΠΩ)+ H2 These measurements provide a route not just to product quantum state population distributions, but also to kinetic energy release distributions, which provide information about scalar pair correlations between the internal excitation in the probed fragment (OH in the above example) and the co-product (H2), to angular scattering distributions (a two vector (k,k’) correlation proportional to the differential cross-section), and angular momentum polarization distributions (a (k,k’,j’) three vector correlation proportional to the polarization dependent differential cross-sections). Examples will be provided from both our LIF and ion-imaging work. [1] M. Brouard, A.P. Clark, C. Vallance, O.S. Vasyutinskii, J. Chem. Phys. 119, 771, (2003). [2] M. Brouard, P. O'Keeffe, C. Vallance, J. Phys. Chem. A, 106, 3629, (2002). * email address: mark.brouard@chemistry.ox.ac.uk

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Photodissociation Dynamics of Polyatomic Molecules

Containing Sulfur: An Experimental Study

F. J..Aoiz 1, L. Bañares, J. Barr, I. Torres, G. A. Pino, G. A. Amaral

Departamento de Química Física I. Facultad de Química. Universidad

Complutense de Madrid. 28040 Madrid. Spain

The photodissociation of the deuterated dimethyl sulfide, CD3SCD3 (DMS), and dimethyl

sulfoxide, CD3SOCD3, DMSO, have been studied at several wavelengths in the UV region

(204-227 nm) using REMPI and time-of-flight mass spectrometry (TOFMS) to measure TOF

profiles, rotational and vibrational REMPI spectra and rotational alignment of the CD3

fragment. The photodissociation of the DMS molecule has been studied in the first (215-230

nm) and the second (200-205 nm) absorption bands. In both cases, the analysis of the TOF

profiles indicates a strongly anisotropic photodissociation (β=-0.9) with a large fraction

(70-80% and 90%, respectively) of the available energy appearing as fragment recoil

translation. In the first absorption band, this fraction is strongly dependent on the excitation

wavelength, supporting the theoretical conjecture [1] that the photofragmentation occurs via

an indirect, albeit rapid, process, involving two strongly coupled excited electronic states and

a non-adiabatic decay [2]. The dissociation in the second absorption band seems to take place

in a single purely repulsive potential energy surface.

The analysis of the results for the photodissociation of DMSO shows that there exist, at least,

three channels leading to formation of CD3. The primary dissociation, S-C bond cleavage,

involves two competing channels with distinct translational energy distributions for the CD3

fragment. The major dissociation pathway, yielding relatively slow and isotropic CD3

fragments, proceeds in a statistical manner on the ground electronic surface following internal

conversion. The second channel (parallel transition) produces a small percentage of

anisotropic and faster CD3 through direct dissociation. By analysing the TOF profiles at

different polarization angles of the dissociation laser and the rotationally-state resolved CD3

REMPI spectra, it has been possible to identify the percentage of the anisotropic dissociation.

[1] M.R. Manaa and D. R. Yarkony, J. Am. Chem. Soc. 116,11444 (1994)

[2] J. Barr, I. Torres, L. Bañares, J. E. Verdasco, and F. J. Aoiz, Chem. Phys Lett. 373, 550

(2003).

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Photodissociation of Simple Aromatic Molecules Studied by Multimass Ion Imaging Techniques

Chi-Kung Ni

Institute of Atomic and Molecular Sciences, Academia Sinica, P. O. Box 23-166, Taipei,

Taiwan

An overview of our recent experimental studies of aromatic molecules using multimass

ion imaging technique will be presented. Photodissociation of several simple aromatic

molecules, including benzene, fluorobenzene, toluene, m-xylene, ethylbenzene,

propylbenzene, phenol, pyridine, 4-methylpyridine, and aniline at 248 nm or 193 nm were

investigated under collisionless condition. Photofragment translational energy distributions

and dissociation rates were recorded. They revealed new isomerization and dissociation

channels of these molecules. The experimental data will be discussed in reference to the ab

initio potential energy surfaces and statistical theory results.

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Spectroscopy and Dynamics of NH Radical Complexes

Galina Kerenskaya, Udo Schnupf, and Michael C. Heaven

Department of Chemistry, Emory University, Atlanta, GA 30322, USA

Spectroscopic and theoretical studies of the binary complexes of NH with He, Ne, and H2

are described. Interest in the NH-He complex stems from identification of NH(X) as a

promising candidate for studies of ultra-cold molecules (paramagnetic ground state with a

large rotational constant). With He buffer gas cooling the stability of NH in a magnetic trap

depends on the details of the NH+He interaction potential. We have probed this interaction

through studies of the A-X transition of NH-He. Preliminary observations appear to be in

good agreement with the results of recent high-level theoretical calculations1.

Studies of the A-X system of NH-Ne yield insights concerning the characteristic energy

level patterns of 3Σ and 3Π complexes. Theoretical predictions have been used to guide the

analysis of the congested ro-vibronic structure of NH(A)-Ne. The predictions were in

qualitative agreement with the observed structure, but systematic quantitative errors were

noted. Interestingly, contrasting errors were found for the singlet (a and c) and triplet (X and

A) potential energy surfaces.

Complexes of NH with H2 are of interest as they may be used to examine NH+H2→NH2+H

reaction dynamics. This reaction is endothermic for NH(X), so the existence of a stable

NH(X)-H2 complex is expected. Quenching data indicate that the reactions of NH(c) and

NH(A) with H2 do not encounter barriers. Preliminary work on NH-H2 shows that the

ground state complex may be generated in a jet expansion and detected via excitation of the

monomer A-X transition. The spectral features observed to date involve direct excitation of

the continuum. They define a ground state bond dissociation energy of "0D =35 cm-1.

Experiments are in progress to determine the primary decay channels for the non-fluorescent

quasi-bound levels of NH(A)-H2.

1. H. Cybulski, R. V. Krems, H. R. Sadeghpour, A. Delgarno, J. Klos, G. C. Groenenboom,

A. van der Avoird, D. Zgid and G. Chalasinski, work in progress.

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Molecules in Cold Atomic Gases: How do They Interact?

Jeremy M. Hutson and Pavel Soldán

Department of Chemistry, University of Durham, Durham DH1 3LE, United Kingdom There is great interest in cooling molecules and trapping them at temperatures below 1 milliKelvin and especially in producing quantum-degenerate gases of dipolar species. Over the last few years, several experimental methods have been developed to cool stable molecules and free radicals to temperatures of tens or hundreds of milliKelvin. These include buffer gas cooling in cryogenic helium [1], molecular beam decleration using switched electric fields [2], guiding of the cold fraction from a thermal gas [3], and crossed molecular beam scattering [4]. However, the cold molecules produced by such methods need further cooling to reach the ultracold regime below 1 milliKelvin. One promising candidate for this “second stage” cooling is to inject the cold molecules into a cold atomic gas of Rb or some other alkali metal and to rely on “sympathetic cooling” of the molecules. However, very little is known about the interactions between molecules and alkali metal atoms. We have investigated the interaction between Rb and polar molecules such as NH and OH. We have carried out ab initio electronic structure calculations to characterize the surfaces. The strength of the interaction is found to depend very strongly on the spin states involved. For example, if Rb and NH collide with their electron spins parallel, they interact on a quartet surface (4A''). The interaction is then dominated by dispersion forces and is relatively weak, with a well depth of 0.078 eV. If the two species are not spin-aligned, however, they can interact on the lowest doublet surface (2A''), which has a very much stronger interaction potential (well depth 1.372 eV) because it is an ion-pair state with an attractive Coulomb interaction at short range. The dispersion-bound doublet state crosses the ion-pair state at conical intersections at linear geometries. In this case, strong collisions can occur via a harpoon mechanism. This effect may be undesirable for sympathetic cooling, because it may enhance reorientation and three-body collision rates, but it might also be used for production of extremely polar ultracold molecular complexes. For RbNH, there are electronically excited states correlating with Rb (2P) that have reasonable Franck-Condon factors to both the low-energy continuum state Rb (2S) + NH(3Σ) and the ion-pair bound state Rb+NH–. It may thus be possible to form the very polar Rb+NH– species by stimulated Raman pumping or even by spontaneous emission. Similar deeply bound ion-pair states exist for other alkali atom – molecule pairs such as Rb–OH, but not for Rb–HF. References [1] J. D. Weinstein, R. deCarvalho, T. Guillet, B. Friedrich and J.M. Doyle, Nature 395, 148 (1998). [2] H. L. Bethlem and G. Meijer, Int. Rev. Phys. Chem. 22, 73 (2003). [3] S. A. Rangwala, T. Junglen, T. Rieger, P. W. H. Pinkse and G. Rempe, Phys. Rev. A 67, 043406 (2003). [4] M. S. Elioff, J. J. Valentini and D. W. Chandler, Science 302, 1940 (2003). [5] P. Soldán and J. M. Hutson, Phys. Rev. Lett. 163202 (2004).

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Optical Stark and Zeeman Spectroscopy of Transition Metal Containing Radicals

Timothy C. Steimle

Department of Chemistry and Biochemistry Arizona State University

Tempe, AZ 85287-1604, U. S. A.

Identification and characterization transition metal (TM) metal containing radical molecules formed in the reaction of TM atoms or clusters with simple gaseous reagents provide insight into corrosion and catalysis. As is evident from the multitude, and variety, of molecules identified using time-of-flight mass spectrometry, the difficulties of synthesizing these ephemeral molecules in the gas phase has largely been overcome by implementing the laser ablation/gaseous reagent supersonic expansion schemes. Generating collimated molecular beams and recording the resonant optical spectra at near natural linewidth limits for the multitude of diatomic molecules produced in these sources is now relatively straightforward. The ground and excited electronic state permanent electric dipole moments, extracted from analyzing these optical spectra recorded in the presence of a static electric field, have been used to establish trends in chemical bonding. The results of our Stark measurements for diatomic TM nitrides, oxides and carbides will be presented and compared with simple molecular orbital correlation models and sophisticated ab initio predictions.

The number of TM-containing polyatomic molecules for which ultrahigh resolution electronic spectra have been recorded and analyzed is relatively small due in part to the traditional reliance upon LIF detection. Most notable exceptions are the studies of the dihalides by the Oxford group [1] and the cyanides [2] and methylidynes [3] from by the UBC group. Recently detected of PtNH and ScCN will be given as examples from our laboratory. Efforts to apply the absorption-based technique of transient frequency modulation spectroscopy [4, 5] to the study of these TM containing polyatomic as well as other diatomic molecules will be summarized.

Although less frequently implemented, optical Zeeman spectroscopy can also provide valuable insight in the nature of the electronic states through the determination of magnetic g-factors. Results of our recent optical Zeeman spectroscopic measurements on the A 3Φ - X 3∆ band system (“γ-band”) of TiO and the A2Π/B2Σ+ - X2Σ+ band systems of calcium monohydride, CaH, will be presented. These molecules are proposed as probes of the ambient magnetic field in the sun [6]. The goal here is twofold: a) determine magnetic tuning rates for visible and near infrared spectral features, b) use the extracted g-factors to analyze the electronic state composition. 1. S. Ashworth and J.M. Brown, J. Mol. Spectrosc. 191, 276-285 (1998). 2. C.T. Kingston, A.J. Merer, T.D. Varberg, J. Mol. Spectrosc. 215(1), 106-127 (2002). 3. M. Barnes, A.J. Merer, and G.F. Metha, J. Mol. Spectrosc. 181, 168-179 (1997) 4. J.C. Bloch, R.W. Field, G.E. Hall, and T.J. Sears, J. Chem. Phys. 101, 1717-1720 (1994). 5. T.C. Steimle, M. L. Costen, G.E. Hall, and T. J. Sears, Chem. Phys. Lett, 319, 363-367

(2000). 6. S. V.Berdyugina, and S. K.Solanki, Astronomy and Astrophysics 385(2), 701-715 (2002)

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The Bending Vibrational Levels

of C3-Rare-Gas Atom Complexes and C2H2+ Yen-Chu Hsu1,2

1Institute of Atomic and Molecular Sciences, Academia Sinica, P. O. Box 23-166, Taipei 106, Taiwan, R. O. C.

2Department of Chemistry, National Taiwan University, Taipei 106, Taiwan, R. O. C.

Bending vibrations of polyatomic molecules have a strong influence on molecular dynamics since they can lift the degeneracies of electronic states and/or cause state mixings. They are not always easy to observe since they often have low frequencies. The bending levels of two molecular systems have been studied in this work: C3-rare gas van der Waals complexes and the acetylene cation, C2H2+. The bending vibrational levels (υb=1-10) of the ground states of the C3-rare gas complexes were probed by wavelength-resolved emission from several vibronic levels of the à state.[1] The level structure of the two bending vibrations of each complex, except that of C3-Ne, has been fitted to a perturbed harmonic oscillator model, where the potential function has the form θ+θ= 2221 coscos rVrVV ( r is the amplitude of the C3-bending motion and θ gives the orientation of the rare gas atom relative to the plane of the bent C3 molecule). The potential function of each complex, obtained from the model fit, will be compared with that from our ab initio calculations. The trans- and cis