DISSOCIATIVE ELECTRON ATTACHMENT IN MOLECULES - NEEDS AND CURRENT

STATUS OF AVAILABLE DATA

Iztok ČadežJožef Štefan Institute, Jamova cesta 39, 1000

Ljubljana, Slovenia E-mail: iztok.cadez@ijs.si

Regional workshop on atomic and molecular data, Belgrade, Serbia, June 14-16, 2012

Outline

DISSOCIATIVE ELECTRON ATTACHMENT IN MOLECULES - NEEDS AND CURRENT STATUS OF AVAILABLE DATA

- Introduction- Historic overview- DEA in some details (TCS, PCS, I(θ),…)- Applications and needs- Available data- Perspectives

Introduction

Many types of elementary collision processes for numerous atomic particles are needed to be well known for the variety of collective phenomena to be understood.

Here we will present only fragmentary, personal view on one of such processes, dissociative electron attachment, which is one channel of one kind (resonant) of one pair of collision partners (electron + neutral molecule).

Introduction

e + AB {AB-} A + B-

• A, B – atoms or atomic groups; • a resonant process – specific peaked energy

dependence, typ. < 15 eV(!); • alternative compound state decay by

autodetachment – resonant electron scattering);• symmetry selection rules – angular distribution

of dissociating fragment;• energy partition among kinetic and internal

degrees of freedom;• temperature dependence – DEA to excited

target.

Introduction

e + AB {AB-} A + B-

Anzai et al., Cross section data sets for electron collisions with H2, O2, CO,CO2, N2O and H2O, Eur. Phys. J. D (2012) 66: 36

Historic overview

First experimental evidence of DEA

J. T. Tate and P. T. Smith, Phys. Rev. (1932) 39 270

Historic overview

• In late fifties a strong interest for DEA started• Early the most active centers for DEA research:

– Bell Telephone Labs. – H. D. Hagstrum (1951)– Westinghouse Labs. – G. J. Schulz, P. J. Chantry (1959-

1968)– USSR – V. I. Khvostenko, V. M. Dukel’skii, I. S.

Buchelnikova (1957-)– Liverpool University – J. D. Craggs (1959)– NBS/JILA (G. Dunn – 1962)– Lockheed Missiles and Space Comp. – D. Rapp et al.

(1965)– Yale University - G. J. Schulz, and his group (1967-

1981)– University Orsay, Paris – F. Fiquet-Fayard (1972)

• First theoretical approaches borrowed from nuclear science (J. N. Bardsley, A. Herzenberg, T. F. O’Malley, H. S. Taylor, Yu. N. Demkov) (1962-).

Historic overview

The study of atomic collisions in Belgrade started after the return of Milan Kurepa from postgraduate visit in the laboratory of professor J. D. Craggs at the University of Liverpool in 1963. Soon after this, Vladeta Urošević (electron impact photo-excitation and swarms, IFB) and Branka Čobić (heavy- particle collisions, Vinča) entered actively in the field.

Milan Kurepa (1933-2000)

Soon also started very active theoretical work initiated by Ratko Janev (Vinča) after his return from Ph.D. stay in Lenjingrad (StPetersburg) and Petar Grujić after his return from Ph.D. stay at UC, London.

Good seed + good soil + good “weather” conditions Good seed + good soil + good “weather” conditions (environment) + good timing (goals) + dedicated work (environment) + good timing (goals) + dedicated work = plenty of good results! = plenty of good results!

Historic overview

• Later development of DEA research included detailed partial CS determination from triatomic and some bigger molecules, study of angular distribution of product anions and temperature dependence of DEA CS.

• After somehow lower intensity of this research in eighties and nineties new “boom” occurred in more recent time by development of COLTRIMS concept and position sensitive detection and driven by new areas of interest.

• Theory has been steadily developing and following new experimental findings.

Present time key experimental tool - VMI

Wu et al., Rev. Sci. Instrum. (2012) 83 013108

Adaniya et al., Rev. Sci. Instrum. (2012) 83 023106

Nandi et al., Rev. Sci. Instrum. (2005) 76 053107

Historic overview

Present key experimental tool - VMI

Adaniya et al., Rev. Sci. Instrum. (2012) 83 023106

Historic overview

Total cross section measurements

Experimental studies were initially concentrated on the relative and absolute cross section measurements for total anion production.

Christophorou et al., 1984.

Čadež, Pejčev and Kurepa, J. Phys. D: Appl. Phys. (1983) 16 305

Tate-Smith type apparatusTate-Smith type apparatus for TCS, incorporating TEM was constructed in Belgrade in early seventies. Studied molecules were O2, CO2, CCl2F2, BF3, Cl2, Br2, SO2 and some more.

Total cross section measurements - H2

case

e + H2(v) → H2-* → H + H -

0 2 4 6 8

0

5

10

15

H(n=1) + H-

H(n=2) + H-

Po

ten

tia

l [ e

V ]

Internuclear distance [ a.u. ]

H2

- X 2u

+

H2

- "2" 2u

+

H2 X 1

g

+Ee

13.93eV

3.73eV

EAH

= 0.754 eV

H + H

H2

- "1" 2g

+

E. Krishnakumar, S. Danifl, I. Čadež, S. Markelj and N. J. Mason, PRL 106 (2011) 243201

H2

D2

Isotope effect is common in DEA as atomic mass determines the speed of dissociation and therefore brunching to this channel of resonant decay. This is the most pronounced for H vs. D – 100% of mass difference!

This case spans over almost This case spans over almost entire period of modern time entire period of modern time

DEA studies!DEA studies!

Partial cross section measurements

Coupling with fragment ion mass analysis allowed determination of partial cross section for production of particular negative ion.

Braun et al., Int. J. Mass Spec. (2006) 252 234;

Inter laboratory cooperation on specific Inter laboratory cooperation on specific target is very important and fruitful!target is very important and fruitful!

From: Matejčík et al. Int. J. Mass Spec. (2003) 223-224 9

Such arrangements are/were used at Yale, Innsbruck, Bratislava, Berlin, Belgrade...

Angular distribution of fragment anion

For diatomics very clear interpretation as AD is a mirror image of attachment probability – fast dissociation along molecular axis (O2, NO, CO, H2).

From: Van Brunt and Kieffer, Phys. Rev. A (1970) 2 1293 & 1899

O-/CO: Čadež et al., J.Phys.B. (1975), 8 L73; Hall et al., Phys. Rev. A (1978), 15 599; Schermann et al., J.Phys.E., (1978) 11 746

Angular distribution of fragment anion

Charm of the experimental studies of atomic Charm of the experimental studies of atomic collisions is permanent development of elegant collisions is permanent development of elegant and more or less simple technical and more or less simple technical improvements!improvements!

Modifying standard electron spectrometer by incorporating simple momentum filter for elimination of electrons allowed high resolution ion energy and angular measurements!

H-/H2O: Haxton et al., 2006 (theory); Adaniya et al., 2012 (experiment)

Angular distribution of fragment anion

• For small polyatomics interpretation more difficult due to complicated few body motion – consequently, much less studied (H2O, H2S).

• For big biomolecules, interpretation is again easier due to large mass of neutral fragment – remains to be studied and it has very high importance for dense media.

Energy partition

Measurement of fragment ion energy allows determination of the excited state in which neutral fragment is left.

Hall et al., Phys. Rev. A (1978) 15 599

H- from H2OBelić et al., J.Phys.B: (1981) 14 175

Ee + Ei-ex = Ef-ex + Ek + D - EA

EKB- = MA/MAB * EK

e + AB {AB-} A + B-

Most atoms and many radicals have positive EA.

DEA to excited target

Spence and Schulz, Phys. Rev. (1969) 188 280

Brüning et al. (1998) Chem. Phys. Lett. 292 177

Henderson, Fite and Brackmann, Phys.Rev. (1969) 183 157

First observed temperature dependence of DEA studied in O-/O2. Later DEA in CO2, N2O, H2, D2, HCl, DCl, HF, Na2, CCl4, CCl2F2, …

Electron collisions with excited targets are frequent in hot mediaElectron collisions with excited targets are frequent in hot media – an – an overview in L. C. Christophorou and J. K. Olthoff, overview in L. C. Christophorou and J. K. Olthoff, Electron interactions with Electron interactions with excited atoms and moleculesexcited atoms and molecules, Advances in Atomic, Molecular and Optical , Advances in Atomic, Molecular and Optical Physics, vol. 44, Academic Press 2001.Physics, vol. 44, Academic Press 2001.

Temperature dependence – H2 case

E (4eV) + H2(v) H2-* H + H -

Theoretical CS for DEA in H2(v, J=0) (Horaček et al. 2004) (o) and DEA CSs to some molecules from Christophorou et al., 1984.

Allan and Wong, PRL (1978) 41 1791

Very strong CS dependence on internal ro-Very strong CS dependence on internal ro-vibrational excitation and also isotope effect! vibrational excitation and also isotope effect!

Very strong temperature dependence of DEA Very strong temperature dependence of DEA also in HCl, DCl and HF.(Allan and Wong, 1981). also in HCl, DCl and HF.(Allan and Wong, 1981).

14 eV H-/H2&D-/D2: Čadež et al., J.Phys.B. (1988) 21 3271; Hall et al. PRL (1988) 60 337, Schermann et al., J.Chem.Phys. (1994) 101 8152

Temperature dependence – DEA to excited target

D2

H2

Markelj and Čadež, J. Chem. Phys.(2011) 134 124707

DEA to electronically excited target

O-/O2*: Belić and Hall, J.Phys.B (1981) 134 124707.

DEA in SO2*: Krishnakumar et al., Phys. Rev. A (1997) 56 1945.

Also to specific vibronic states of SO2*: Kumar et al. Phys. Rev. A (2004) 70 052715.

The way of experimental development

Some mistakes are indispensable on the way and they Some mistakes are indispensable on the way and they contribute to the charm of scientific development!contribute to the charm of scientific development!

• “no temperature dependence of CS in H2”

• C2H2 second peak – C- H-

• CS for H-/CH4

• Signal background (H-/H2, D-/D2)

• Influence of electron energy resolution, momentum transfer, target gas temperature on experimental result.

Total clearness of results and perfect agreement between the Total clearness of results and perfect agreement between the theory and experiment is an ultimate goal but the quest for this theory and experiment is an ultimate goal but the quest for this goal is sometimes a way to errors.goal is sometimes a way to errors.

The way of experimental development

0

30

60

90

120

150

180

210

240

270

300

330

gas beam

nMOMTRA3.OPJ

H2 ; Ee = 14 eV ; T = 300 K

isotropic gas cos() - beam

cos()2 - beam

e - beam

Transfer of the momentum of incident electron to the target is often overseen although it is not negligible – in modern momentum imaging it is clearly visible and normally taken into account.

DEA – theoretical description

There are two energy manifolds one for the neutral target molecule and another for compound negative ion. Particle, that connects these two manifolds is electron – basically, satiation is similar to what one has in elementary particle physics!

The theory describes different aspects of resonant electron-molecule collision:

- Energy levels of neutral molecules (common for all molecular spectroscopy).

- Energy levels of negative ion compound molecule (unstable!) – both real part and decay width. For both cases energy levels are function of molecular shape parameters (bond lengths and bond angles).

- Time evolution of compound molecule – typically on fs level.

- Extraction of cross sections for particular decay channel, resonant scattering and DEA.

DEA – theoretical description

First theories were taken from, then, more advanced nuclear physics.Later, very sophisticated theories developed for molecular resonances:

- Local complex potential - resonant state dependent only on R.

- Non-local complex potential – resonant state dependent on R and Ee.

- Wave packet propagation in local complex potential.

- Ab initio calculations of compound state parameters.

DEA – theoretical description

DEA in polyatomic molecules – C2H2

Recent detailed theoretical analysis of DEA in acetylene: e + C2H4 C2H- + H

Chourou and Orel, Phys.Rev.A (2008) 77 042709

Applications and needs

Where is DEA present?Where is DEA present?

- As a binary collision process in rarefied in rarefied mediamedia where free electrons are present.

- The basic physical mechanism of DEA – resonant electron capture to a molecule and subsequent bond breaking, occurs also on on surfaces and in dense mediasurfaces and in dense media.

The later relevance drives main interest The later relevance drives main interest for DEA in the present time!for DEA in the present time!

Applications and needs

Particular example – fusion plasma:

- Relatively small number of molecular species in edge plasma but still relevant process – H2, D2, T2, HD, HT, DT and also hydrocarbons – satisfactory data base exists (e.g. http:\\www. eirene.de – Juel Reports 3966, 4005, 4038, 4105; R. K. Janev, D. Reiter and U. Samm).

- New development due to ITER material mix (Be and New development due to ITER material mix (Be and W compounds) but in particular processes with W compounds) but in particular processes with nitrogen – Nnitrogen – N22, NH, NH33, … and isotopologues., … and isotopologues.

- Besides being important for the plasma properties, it is potentially relevant to specific collision processes related to impurity transport and interaction with surfaces – deposition and desorption).

DEA in rarefied media - DEA in rarefied media - Modelling of ionized gases (BF3, SF6, CH4, SiH4, …)

Sensitivity on vibrational excitation of H2 from the wall1-D Monte-Carlo model for neutral particle transport (Kotov and Reiter,

2005)

10-5

10-4

10-3

10-2

10-1

100

H2(

v) p

opul

atio

n (c

m-3

)43210

Distance from wall (cm)

v=0

1

H2

23

4

5

67

89

Te=2.0eV

ne=1014

cm-3

nH2=1.0 cm-3

573K at wall

10-5

10-4

10-3

10-2

10-1

100

H2(

v) p

opul

atio

n (c

m-3

)

43210

Distance from wall (cm)

v=0

1

H2

23

4

5

6

7

8

9

Te=2.0eV

ne=1014

cm-3

nH2=1.0 cm-3

573K at wall

All H2 from the wall in v=0

H2(v) from the wall to edge plasma

All H2 from the wall in v=4

1017 m−3 < ne < 1020 m−3, 1eV < Te < 100 eV, 10−3 ne < nI < 10−1ne, nHo ≈ 10−3ne

This is a classic example of application of DEA for plasma This is a classic example of application of DEA for plasma developmentdevelopment

From : M. Bacal, Nuclear Fusion 46 (2006) S250

Applications and needs

Rarefied media – Rarefied media – Volume H- (D-) ion sources

From : M. Bacal, Nuclear Fusion 46 (2006) S250

Applications and needs

Rarefied media – Rarefied media – Volume H- (D-) ion sources

Vibrationally excited H2 are precursor for HH-- ion production by ion production by DEADEA

They are produced by• e-V:e-V: H2 + e (slow) H2(X 1g

+, v’’) + e

• E-VE-V: H2 + e (fast) H2(B 1u+,C 1u) H2(X 1g

+, v’’) + h

• Cascade:Cascade: H2(X 1g+, v=0) + e H2(E, F 1g

+)

H2(B 1u+) H2(X 1g

+, v’’) + h

• Recombinative desorption:Recombinative desorption: H + H + wall H2(X 1g+ , v’’ = 1,

2)

followed by the E-V excitation of the X1g+ state with the low v’’:

H2(X 1g+, v’’ = 1, 2) + e (fast) H2(B 1u

+,C 1u)

H2(X 1g+, v’’ 1, 2) + h

READ – Reversed Electron Attachment READ – Reversed Electron Attachment DetectorDetector

From :Boumsellek and Chutjian. 1992 and Darrach et al. 1998

Applications and needs

Rarefied media - Rarefied media - Sensitive gas detectors

Low energy electron attachment is very efficient to producing characteristic anions for low level pollution monitoring.

Applications and needs

Rarefied media - Rarefied media - Aeronomy and astrochemisty (from Earth and other planetary atmospheres to cosmology)

DEA is potentially important in the environments where low energy electrons are present and neutral molecules and radicals – mainly indirect evidence from modelling.

L. Campbell and coworkers have been showing the importance of accurate data on e-molecule collisions for actrochemistry modelling.

2 3 4 5 6 7 8 9 10 11

H2 C3 c-C3H  C5 C5H  C6H  CH3C3N  CH3C4H  CH3C5N?  HC9N 

AlF  C2H l-C3H  C4H l-H2C4 CH2CHCN  HCOOCH3 CH3CH2CN  (CH3)2CO 

AlCl  C2O C3N  C4Si C2H4  CH3C2H  CH3COOH  (CH3)2O  NH2CH2COOH ? 12

C2 C2S C3O  l-C3H2 CH3CN HC5N  C7H CH3CH2OH  C6H6

CH  CH2 C3S  c-C3H2 CH3NC  NH2CH3 H2C6 HC7N 

CH+  HCN C2H2 CH2CN CH3OH HCOCH3 CH2OHCHO  C8H  13+

CN HCO CH2D+ ?  CH4 CH3SH  c-C2H4O  HC11N

CO HCO+ HCCN  HC3N HC3NH+  CH2CHOH  PAHs

CO+ HCS+ HCNH+  HC2NC HC2CHO  C60+

CP HOC+ HNCO HCOOH NH2CHO

CSi  H2O HNCS  H2CHN C5N 

HCl  H2S HOCO+  H2C2O

KCl  HNC H2CO H2NCN

NH HNO H2CN  HNC3

NO  MgCN H2CS SiH4

NS  MgNC H3O+ H2COH+

NaCl N2H+ NH3

OH N2O SiC3

PN  NaCN

SO OCS

SO+  SO2

SiN  c-SiC2

SiO  CO2

SiS  NH2

CS H3+

HF SiCN

SHFeO

AlNC

>160 Interstellar Molecules

National Radio Astronomy Observatory, (http://www.cv.nrao.edu/~awootten/allmols.html

The number of molecular species observed in various regions in space is steadily increasing

(Adapted from N. J. Mason, 2010)

Role of anions - data needs for modelling

Hydrocarbon anions are observed in different environments in space (e.g. Millar et al., 2007, Harada&Herbst, 2008) and detailed modelling of these requires data for various processes.

Result of modeling of the time evolution of CnH and CnH- following the evaporation of methane ice as applied to explain the observations from L1527, an envelope of a low-mass star-forming region - from Harada&Herbst, 2008.Recent relevant study of DEA in H−C≡C−C≡C−H by May et al. PR A 77,

040701R (2008) and on RVE by Allan et al., PR A 83, 052701 (2011)

Planetary atmospheres – Titans in particular

Composition ≈ 97% N2 + 2% CH4 + 1% C2H2, C2H4,….Ar(?)

From: S. Atreya, Titan Workshop, Kauai, 12. April 2011http://www.chem.hawaii.edu/Bil301/Titan2011.html

V. Vuitton et al., Negative ion chemistry in Titan’s upper atmosphere, Planetary and Space Science 57 (2009) 1558–1572

Role of anions - data needs for modelling

- The Electron Spectrometer (ELS), revealed the existence of numerous negative ions in Titan’s upper atmosphere. - Up to 10,000 amu/q, two (three) distinct peaks at 22 ± 4 and 44 ± 8 (and 82 ± 14 ) amu/q,- Ionospheric model of Titan including negative ion chemistry. - DEA mostly to HCN initiate the chain of reactions.

- Radiative electron attachment is fast for bigger carbon chain molecules as for C6H but very slow for light ones.- Anions from thermal energy electron capture – not taken into account.- Data for DEA are used (CH4,C2H2, estimate for C4H2 and C6H2. - Ion pair production by photons (but not by electrons)- Photo-detachment, cation-anion recombination, anion-neutral associative detachment.- Proton transfer is very efficient (e.g. H- + C2H2 →C2H- + H2).- Polymerization (e.g. C2nH- + C2H2 → C2n+2H- + H2).

5 10 15 20

0,0

0,1

0,2

0,3

0,4

0,5

AP

(CH

3+ +H

- )-M

itsuk

e_93

No

rm.

ion

yie

ld

Electron energy [eV]

CH4 - H

2O

H2O-fit

CH4

5 10 15 20

0,00

0,05

0,10

0,15

0,20

0,25

C2H

2

Nor

m. i

on y

ield

Electron energy [eV]5 10 15 20

0,0

0,1

0,2

0,3

0,4

0,5

0,6

Nor

m. i

on y

ield

Electron energy [ eV ]

C2H

4

5 10 15 200,0

0,1

0,2

0,3

0,4

AP

(C2H

5+ +H

- )-M

itsuk

e_93

Nor

m. i

on y

ield

Electron energy [ eV ]

C2H6

5 10 15 200,0

0,1

0,2

0,3

0,4

AP

(C3H

7+ +H

- )-M

itsuk

e_93

No

rm.

ion

yie

ld

Electron energy [eV]

C3H

8

Low energy H- yield from DEA to small hydrocarbons

Potential relevance of DEA to small Potential relevance of DEA to small hydrocarbons stimulated an experimental hydrocarbons stimulated an experimental study of the low energy Hstudy of the low energy H-- ion yield from ion yield from some small HCs. some small HCs.

Two processes contribute:Two processes contribute:-- Dissociative electron attachment for Ee Dissociative electron attachment for Ee <15 eV<15 eV- Polar dissociation (ion pair production) Polar dissociation (ion pair production) for Ee > 15 eV.for Ee > 15 eV.

Activity within COST CM0805 – The Activity within COST CM0805 – The Chemical cosmosChemical cosmosČadež, Rupnik and Markelj, Eur. Phys. J. D (2012) 66:

73

Applications and needs

Similar resonant states exist in molecules incorporated in dense media but their properties (energy, symmetry and lifetime) are modified:- by substrate if adsorbed on the surface- by the close neighbor molecules (thick layers, clusters, in the bulk).

Different scenarios occur regarding released anion from DEA - it can be emitted out of the system (e.g. condensed layers) or can induce further reactions.

Dense media and surfacesDense media and surfaces

DEA at surfaces – dense layers

Group of R. E. Palmer at the University of Birmingham: molecule manipulation by STM at room temperature

Some public titles following the Some public titles following the paper in Nature (Google):paper in Nature (Google):

- “Quantum electron “submarines” - “Quantum electron “submarines” help push atoms…” - (New help push atoms…” - (New Scientist)Scientist)- “Nano-surgeons break the atomic - “Nano-surgeons break the atomic bond (The Telegraph)”bond (The Telegraph)”- “Birmingham Scientists Witness - “Birmingham Scientists Witness the Birth of an Atom”the Birth of an Atom”

Sloan and Palmer, Nature 434 (2005) 367

Selective dissociation of chlorine atoms from individual oriented chlorobenzene molecules adsorbed on a Si(111)- 7x7 surface at room temperature.

Proposed two electron mechanism: first electron (b) excites C-Cl wag vibrations (c) and second electron (d) induce dissociation of C-Cl bond. Free Cl sticks to the surface (e).

DEA at surfaces – dense layers

• Group of L. Sanche, Univ. of Sherbrooke, Quebec, Canada• Group of R. Azria, A. Lafosse… , UPS, Orsay, France

DD-- from amorphous ice at 190 K from amorphous ice at 190 KSimpson et al., J.Chem.Phys. 107 (1997) 8668

Lafosse et al., Phys. Chem. Chem. Phys. 8 (2006) 5564–5568

Radiation DamageElectron driven rections

(From E. Illenberger, 2007)

DEA in biomolecules

ThymineThymine

DEA in biomolecules

F. Martin, P. D. Burrow, Z. Cai, P. Cloutier, D. Hunting, and L. Sanche, PRL 93 (2004) 068101

Data – production and needs

UsersModelling

Sensitivity analysisData formatting

DATABASE

Data productionData collection, evaluation and

recommendations

Needs

Data – production and needs

Data productionData production

Experiments of “light”(more individual work) - new processes- basic properties- benchmark cases- new exp. methods

Experiments of “fruit”(more collective work)- choice of subject- application of methods- data production- Interpretation of data

Theory - In-depth explanation of processes - development of models - data production and model evaluation

Data usageData usage

Modelling of complex processes, new technological procedures, processes in other sciences.

Sensitivity analysis

Feedback to data producers.

Data evaluationData evaluation

Collection from all available sources, new and old.

Evaluation of applied methods and claimed accuracy.

Recomdation of best data to be used.

Feedback with data producer.

Recommendations for new measurements or calculations.

Data “shaping”Data “shaping”

Formation of standardised data bases

Appropriate data formats

Accessibility

List of laboratories actively participating in present DEA research

Sherbrooke, Canada (Léon Sanche, biomolecules, surfaces, experiment, theory)Lincoln, Nebraska (Paul Burrow, Gordon Gallup, experiment; Ilya Fabrikant, theory)Davis & Berkeley, CA (Ann Orel, Tom Rescigno, Bill McCurdy : theory; H. Adaniya :

DEA experiment – COLTRIMS)Belfast (Tom Field; Gleb Gribakin, ToF DEA, biomolecules; theory)Innsbruck (Paul Scheier, Tilmann Märk, Stefan Denifl, biomolecules, collisions in He

nanodroplets)Fribourg (Michael Allan)Berlin (Eugen Illenberger, biomolecules)Open University, Milton Keynes (Nigel Mason, Jimena Gorfinkiel, experiment, theory)Bratislava, Slovakia (Štefan Matejčik)University of Podlasie, Poland (Janina Kopyra, electron transport)Prague, Charles University (Jiří Horáček, Martin Čížek, Karel Houfek (+ Wolfgang

Domcke), theory)Orsay (Robert Abouaf, Roger Azria, Ann Lafosse, surfaces)London (JonathanTennyson, R-matrix theory)Island (Oddur Ingólfsson, experiment)Tata Institute, Mumbai (E. Krishnakumar, S. V. K. Kumar, V. Prabhudesai, experiment:

velocity slice imaging)Hefei, China (S. X. Tian, B. Wu, experiment: velocity slice imaging)

(adapted from M. Allan, ICPEAC, 2011)

Current activities

Available data

List is too long to be presented here – only examples:

Diatomic: H2, O2, CO, NO, S2, Cl2, Br2, HF, HCl, HBr

Triatomic: H2O, CO2, CS2, H2S, O3, SO2, N2O, NO2, HCN

Small polyatomic: CH4, NH3, BF3, C2H2, CCl2F2, C6H6, SF6, many chloro- and fluorocarbons, CH3CN, N2O5

Big molecules: C60, HCOOH, C2H5NO2, uracil, glicine, nitrotoluene, cyclopentanone, tetrahydrofuran, HFFA (CF3)2C=N-N=C(CF3)2), tymine, various molecular clusters

Perspectives

• More data on DEA to excited molecules (both, ro-vibrational and electronic) are needed.

• Angular distribution of ions from DEA to larger molecules and experiments on oriented targets.

• Resonances (and DEA) in E&B field. • Applications in future might be related to well

defined time scale of e-impact induced molecular breakdown.

• DEA in dense media is a separate field of research of high importance with its own new experimental and theoretical development.

Collaborations on DEA and acknowledgement

Milan KurepaRatko Janev

Aleksandar StamatovićVlada Pejčev

Florance Fiquet-FayardRichard Hall

Catherine SchermannNada Djurić

Will CastlemanSabina MarkeljNigel Mason

E. Krishnakumar

Some references

• R. E. Palmer and P. J. Rous, Resonances in electron scattering by molecules on surfaces, Rev. Mod. Physics 64 (1992) 383

• S Matejcik, A Kiendler, P Cicman, J Skalny, P Stampfli, E Illenberger, Y Chu, A Stamatovic and T D M¨ark, Electron attachment to molecules and clusters of atmospheric relevance: oxygen and ozone, Plasma Sources Sci. Technol. 6 (1997) 140

• A. CHUTJIAN, A. GARSCADDEN, J.M. WADEHRA, ELECTRON ATTACHMENT TO MOLECULES AT LOW ELECTRON ENERGIES, Physics Reports 264 (1996) 393-470

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