laboratory terahertz spectroscopy of gaseous molecules and ions for herschel, sofia and alma...
TRANSCRIPT
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Laboratory Terahertz Spectroscopy of Gaseous Molecules and Ions
for Herschel, SOFIA and ALMA
Shanshan Yu, Brian Drouin and John Pearson
Copyright 2009 California Institute of Technology. Government sponsorship acknowledged.
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Outline Introduction
Application of molecular spectroscopy in astrophysics Laboratory spectroscopic work needed for Herschel, SOFIA and ALMA Experimental setup Data analysis and modeling
Experiment, data analysis and modeling of Acetylene (C2H2 and C2D2) Protonated water (H3O+) Methylamine (CH3NH2)
Laboratory measurements of interstellar weeds
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Molecular spectroscopy Studying the interaction of light and molecules
Interaction causes molecules to transit from one energy level to another
Molecules absorb light: transit from lower to higher energy level
Molecules emit light: transit from higher to lower energy level
The energy levels of a molecule are quantized and unique
Electronic energy levels (electronic transitions in visible and UV)
Vibrational energy levels (vibration transitions in infrared)
Rotational levels (pure rotation transitions in microwave)
Selection rules govern molecular transitions
Transition dipole moments govern transition intensities
Vibration of the nuclei rotation
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Information contained in high-resolution spectra
Geometries, chemical bonding and electronic structure of molecules (line positions) Temperatures of molecules (relative line intensities) Concentrations of molecules (absolute line intensities)
High resolution spectra of water (H2O) and carbon monoxide (CO) around 2000 cm-1
(Brown et al. Journal of Molecular spectroscopy (2005) 774, 111)
C OCO stretching
H
O
H
H2O bending
Frequency (cm-1 )
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Radio astronomy: cold objects, including interstellar gas and dust clouds (10-200K)
Infrared astronomy: objects colder than stars, such as planets
Optical astronomy: stars, galaxies and nebulae
Ultraviolet, X-ray and gamma ray astronomy: very energetic processes such as binary pulsars, black holes, magnetars
Astrophysical observations
1
/2)(
/
5
kThce
hcT
The Planck function
The Planck function at various temperatures (www.ecse.rpi.edu)The Planck function at various temperatures (www.ecse.rpi.edu)
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Visible vs. infrared images of the constellation Orion
Features that cannot be seen in visible light show up very brightly in the infrared.
Visible Infrared
http://www.ipac.caltech.edu
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Terahertz spectroscopy has historically been a technique challenge: limited radiation sources and detectors
Recent technical advances in terahertz sources and mixers have led to the development of powerful terahertz systems for astrophysics
Terahertz spectroscopy: a new era for the cool Universe
λ(μm) 1.00×10-6 1.00×10-4 1.00×10-3 (3.80-7.80)×10-1 3.00×102 1.00×106
Cosmic Rays γ-Rays X-Rays UV Visible Infrared Microwave Radio
(Hz) 3.00×1020 3.00×1018 3.00×1016 (7.89-3.84)×1014 1.00×1012 3.00×108
(cm-1) 1.00×1010 1.00×108 1.00×106 (2.63-1.28)×104 3.33×10 1.00×10-2
The electromagnetic spectrum
Terahertz
1 terahertz = 1012 Hz = 300 μm = 33.3 cm-1
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Herschel-HIFI (Heterodyne Instrument for the Far-IR) ESA and NASA joint mission Launch: 2009 (3 years lifetime) Telescope: 3.5 meter diameter, <100 K temperature The only space facility dedicated to the terahertz part of the spectrum Spectral coverage: 151–212 μm (1910–1410 GHz); 240–625 μm (1250–480 GHz) Objectives: life cycle of gas and dust
New terahertz telescopes (I)
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SOFIA (Stratospheric Observatory For Infrared Astronomy ) NASA and DLR, German Aerospace Center joint mission
Operation: 2010 (20 years lifetime)
The largest airborne observatory in the world
Telescope: 2.5 meter diameter, 240 K temperature
Spectral coverage: 1–700 μm (300000–430 GHz)
Objectives: identification of complex molecules in space, star birth and death etc.
New terahertz telescopes (II)
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New terahertz telescopes (III)
ALMA (Atacama Large Millimeter/Submillimeter Array)
Global collaboration mission: East Asia, Europe, and North America
Location: Chile, 5000 meters above sea level
Operation: 2012 (50 years lifetime)
Telescope: a system up to 66 high-precision dish antennas
Spectral coverage: 300-9600 μm (1000–31 GHz)
Objectives: the physics of the cold Universe
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Laboratory work needed for these missions (I)
H2 H2+ CH3
+ CH5+ CH4 CH2 3
+ CH2 2 CH3 + CH3 3+ CHm nCH2
+ CH4 + CH4 2+ CH4 3
+CH+H3+C H2 H2 e- e- C+ H2H2 C+ H2 H2 H2h H2
CH3 C4+
e-
H2
C+
CH4CH3 2
e- e-
CH2 HCN3 3+
HCN3 HC N2 +1m
HCNe- e-
CH2 5+
CH2 4
HCO2 3+
CO3
CH3+ CO
e- e-
OH+
HO2 +
HO3 +
HO2OH
O
H2
H2
e-e-
NH2 +
N2
CH
CHCO3+ CHOH3 2
+
CHCO2 CHOH3
HCO,CHOH,CHOCH
2
2 5
3 3
COHO2CHOH,3
e-e-
e- e-
CHCNH2 5+
CHCNH3+CHNH3 2
+
HCNH+
HCN
CHNH3 2
CHNH,2 CHCN3
CHCN2 5
NNH3 HCN
CHCN3
e-
e- e-
e-
Interstellar chemistry (Herbst & Klemperer 1973)
Many ions necessary for chemical network to function have not yet been indentified due to lack of laboratory data, e.g. CH2
+, CH3+, NH+, NH2
+, NH3+
Observed molecular ions in space (as of May 2009):Seventeen positive ions: CH+, CO+, SO+, SH+, CF+, HCO+, HCS+, HOC+, N2H+,
H3+, H2D+, HD2
+, HCNH+, HCO2+, H3O+, H2COH+, HC3NH+
Four negative ions: C4H –, C8H –, C3N –, C5N–
Woon, 2007
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Laboratory work needed for these missions (II)
Requiring lab frequency measurements better than 1 MHz for all known molecules to secure identifications of spectral features
Ziurys, 2006
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C2H2
Experimental setup
RF Synthesizer
FM
PC
Source Si bolometer at 2.4 K
Lock-in
Reference
Gas cell
Nine sources: 0.3 - 1.6 THz
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Static quartz cells for stable molecules
Length = 1or 3 m
~100mm
Bomco 2.75" conflatquartz-to-metal seal
25-35 mm
15 o
3 mm thick flat quartz window
Leaking rate: ~1 mTorr/week
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H3O+
DC discharge cell for ions
PumpPrecusors, Ar/He
Coolant out
DC discharge
Coolant In
2 kV, 100 mA
Proton affinity:
H2: 422 KJ/mol
N2: 502 KJ/Mol
CH4: 546 KJ/Mol
CO: ~590 kJ/mol
H2O: 691 KJ/Mol
CH3OH: 754 KJ/Mol
Forming protonated species, MH+: H2 H2
+ + e-
H2+ + H2 H3
+ + H H3
+ + M MH+ + H2
The proton affinity is the energy released in the M+H+ MH+ reaction
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DC glow discharge
A.V. Engel, Ionized Gases, 1965
Voltage
Electric field
Densities of positive charges
Densities of negative charges
Current densities of negative charges
Current densities of positive charges
Positive column: high voltage, high density of negative charges, high current
Negative glow: high voltage, high density of positive charges, low current
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Extended negative glow discharge cell (under development)
2.8 m
2.6 m
ElectrodeElectrode
2.4 M
2.6 M
Courtesy of Prof. T. Amano at U of Waterloo
Keys:
Diameter of the cell
Shape and material of the electrodes
Magnetic field
Low cell temperature (liquid N2 temperature)
Low pressure inside the cell
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Radio frequency discharge cell (under development)
Cell
1.4 MHz 5 kW
10 A100 A
50 CLOADCTUNE
LEXT LANT
Plasma tank circuit
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Data analysis and modeling
Adjust molecular parameters
Calculated positions
Observed positions
Comparison
Molecular parameters
Hamiltonian model
Converge
NO
Yes
Output parameters
)","( JVE
)','( JVE
)","()','( JVEJVE Line positions: 32 )]1([)]1([)1(),( JJHJJDJJBGJVE VVVV
Hamiltonian for 1 states (simplest case):
GV , BV , DV
GV , BV , DV
Perturbation of two states using second order-perturbation theory
)0(2E
E)0(
1E
EVE 2)0(
2
EVE 2)0(
1
)0(
1
)0(2
EV
VE
InteractionV
Fitting software: SPFIT/SPCAT
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Terahertz spectroscopy and global analysis of the bending vibrations of C2H2 and C2D2
Yu et al., Astrophys. J. 698 (2009) 2114-2120 Yu et al., Astrophys. J. (in press)
HC CH
+ +– –
Zero net dipole moment: 0 iiz qz
z
x
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Vibrational modes of C2H2 and C2D2
HC CH
HC CH
HC CH
HC CH
HC CH
3373 cm-1
1974 cm-1
3295 cm-1
612 cm-1
729 cm-1
C2H2
1
2
3
4
5
2705 cm-1
1765 cm-1
2439 cm-1
512 cm-1
539 cm-1
C2D2
5 - 4 117 cm-1 27 cm-1
(~3500 GHz) (~900 GHz)
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Introduction to C2H2
12C2H2 is highly abundant in the interstellar medium Observed in the cold (<100K) gas with abundances from ~10-9 to 10-8 and in the
warm (100-1000K) gas with abundances up to ~10-7 to 10-6 (e.g., Evans et al. 1991; Carr et al. 1995; Lahuis and van Dishoeck 2000; Farrah et al. 2007; Sonnentrucker et al. 2007)
12C2H2 is present as traces in the upper atmosphere of Titan (Coustenis et al. 2007) Jupiter (Ridgway 1974) Uranus (Encrenaz et al. 1998)
12C2H2 is also present as pollutant in The terrestrial troposphere (Kanakidou et al. 1988) the urban atmosphere (Goldman et al. 1981)
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C2D2: a potential interstellar species
Observed multiply deuterated interstellar molecules [D2CO]/[H2CO] = 0.002-0.4 (Turner 1990; Ceccarelli et al. 1998, 2001, 2002;
Loinard et al. 2000, 2001; Parise et al. 2006; Roberts and Millar 2007)
[NHD2]/[NH3] = 0.005-0.05 (Roueff et al. 2000, 2005; Loinard et al. 2001; Gerin et al. 2006)
[ND3]/[NH3] = 0.0005-0.001 (Lis et al. 2002; van der Tak et al. 2002; Roueff et al. 2005)
[CHD2OH]/[CH3OH] =0.06-0.25 (Parise et al. 2002, 2004, 2006)
[CD3OH]/[CH3OH] = 0.01 (Parise et al. 2004)
[D2S]/[HDS] = 0.1 (Vastel et al. 2003)
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Previous studies on C2H2 and C2D2
Spectroscopic information on all the five vibrational modes of C2H2 and C2D2 are available
But Spectroscopic study of 12C2H2 and 12C2D2 in the region of their 5–4 difference bands was very sparse
12C2H2
only ~300 lines measured by FTIR in 52–192 cm-1 with uncertainty of 9 MHz (Kabbadj et al. 1991)
12C2D2
only 10 lines were measured with microwave precisions (Lafferty et al. 1977; Deleon and Muenter, 1987 )
~260 lines were measured in 30–100 cm-1 with uncertainty of 2.4 MHz (Huhanantti et al. 1979; Huet et al. 1991 )
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Experimental setup
150 mTorr C2H2/C2D2 generated by passing H2O/D2O through CaC2 powder
Parabolic mirror
FM
RF Synthesizer
Multiplier chainPC
Si detector
Lock-in
Beamsplitter
Sample cell
Pump
Rooftop reflector
2.8 meters
Sample cellSample
×6×2
×3…
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Observed C2D2 terahertz transitions
1067920 1067950
251 12C2D2 lines observed
12C2D2 5 – 4
802375 802425
12C2D2 25 – (4+5)
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Observed C2H2 terahertz transitions
20 12C2H2 lines observed
10050701005035 1005040 1005045 1005050 1005055 1005060 1005065
Frequency (M Hz)
12C 2H 2 5 - 4 P ff(36)
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Multistate analysis of C2H2 and C2D2
1100
5454ll VV
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Hamiltonian model for C2H2 and C2D2 (I)
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2. Elements representing the vibrational l-type resonance and doubling
3. Elements accounting for the Darling-Dennison type interactions (C2D2 only)
1. Elements responsible for the rotational l-type resonance and doubling
Hamiltonian model for C2H2 and C2D2 (II)
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Block form of the Hamiltonian model for C2D2
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A data set of 2092 transitions was constructed72 parameters fitted to 1938 transitions (154 IR lines rejected) Reduced RMS = 1.3 Microwave RMS = 0.094 MHz (261 MW data)IR RMS = 0.00011 cm-1
Fitting results for 12C2D2
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A data set of 1406 lines was constructed
34 parameters fitted to 1390 transitions
Reduced RMS = 0.5
Microwave RMS = 0.072 MHz (20 MW data)
IR RMS = 0.00016 cm-1
Fitting results for 12C2H2
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Information obtained for the astronomy community
)()('00
0 lNgSl eIeII
: the line position
El: the lower state energy
Eu: the upper state energy
The partition function
0
/
//
,,
23
3
8)('
n
KTEn
KTEb
KTEa
zyxii
n
ul
eg
egeg
hcTS
S': line strength or line intensity
g(-0): line shape function
(Nl): column density
The following parameters can be calculated based on our fitting results:
Which can be used to calculate line strength:
Line strength useful for simulating astrophysical spectra:
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Herschel
ALMA
(cm2/molecule) of the Pee and Ree branch lines of the 5-4 band of C2H2
SOFIA
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Terahertz spectroscopy and global analysis of H3O+
Yu et al., Astrophys. J. Suppl. Ser. 180 (2009) 119-124
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Introduction to H3O+ (I)
H3O+ has a pyramidal structure and is iso-electronic to ammonia (NH3)
NH3: well-known radio frequency (~24 GHz) inversion splitting
H3O+: ground-state inversion splitting of ~1.6 THz
H3O+ is a key molecular ion in interstellar oxygen chemistry
H3O+ + e H2O + H
H3O+ + e OH + 2H; OH + O O2 + H
H3O+ has been detected in the interstellar medium
Orion/KL, OMC-1 and Sgr B2 regions (Hollis et al. 1986; Wootten et al. 1986) OMC-1 and Sgr B2 regions (Wootten et al. 1991) W3 IRS 5, G34.3+0.15 and Sgr B2 (Phillips et al. 1992; Goicoechea &
Cernicharo 2001; van der Tak et al. 2006; Polehampton et al. 2007) Orion/KL, W3(OH), W51 M, and Orion BN-IRc2 (Phillips et al. 1992;
Timmermann et al. 1996; Leratee et al. 2006) Two prototypical active galaxies: M 82 and Arp 220 (van der Tak, 2008)
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Introduction to H3O+ (II)
H3O+ was identified in the laboratory before its discovery in space
Infrared intensity ratios: 1:11:12:3 (Colvin et al 1983)
HH
HO
1: O-H symmetric stretching 2: inversion bending
3: O-H asymmetric stretching 4: perpendicular bending
HH
HO
HH
HO
HH
HO
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Previous infrared studies on H3O+
3: J ≤16 assigned
C and DK determined by observed K-l)=3 forbidden transitions Begemann et al. 1983, 1985; Stahn et al. 1987; Ho et al. 1991; Uy et al. 1997;
Tang & Oka 1999
2: J ≤ 16 assigned 0– – 0+ inversion splitting determined to be 55.3462(55) cm-1
Haese & Oka 1984; Lemoine & Destombes 1984; Davies et al. 1984, 1985; Liu & Oka 1985; Liu et al. 1986; Zheng et al. 2007
1: J ≤ 10 assigned Tang & Oka 1999
4: J ≤ 7 assigned Gruebele et al. 1987
(2+3) – 2 and 22+ – 2
– Davies et al. 1986; Ho et al. 1991
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Previous submillimeter studies on H3O+
4 transitions around 350 GHz measured with an uncertainty of 100 kHz
Plummer et al. 1985; Bogey et al. 1985
24 transitions in 0.9-3.1 THz measured with uncertainties of 0.9-2 MHz by laser sideband spectroscopy
Verhoeve et al. 1988, 1989; Stephenson & Saykally 2005
Jmax=11
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Perturbations in H3O+
Tang and Oka, 1999
In previous studies:
Strong Coriolis interaction between 1 and 3 was not taken into account
About 200 assigned high-J lines could not be fitted
The largest observed-calculated frequency was 4.831 cm-1
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Experimental setup
H2O: 30 mTorr, H2: 5 mTorr
DC discharge: 80 mA, 2 kV
Cell temperature: 230 K
Magnetic field: 150 Gauss
Coolant out
Discharge
H2O, H2 Coolant in
Sample cell
Pump
BeamsplitterRooftop reflector
FM
Rf Synthesizer Multiplier chain
PC
Si detector
Lock-in
×6×2
×3…
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Observed H3O+ terahertz transitions
11 34
Observed for the first time
8 H3O+ lines observed
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Multistate analysis of H3O+
0 - (55 cm -1 )
2-(954 cm -1 )
2+ (581 cm -1 )
2(A 1 )
2
3
1- (3491 cm -1 )
1+ (3445 cm -1 )
45
1 (A 1 )
0 +
3-(3574 cm -1 )
3+ (3536 cm -1 )
l=1 l= -1 l=1 l= -1
6789
3(E)
4-(1693 cm -1 )
4+ (1626 cm -1 )
10111213
l=1 l= -1l=1 l= -1
4(E)
0 1
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Block form of the Hamiltonian model for H3O+
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Fitting results for H3O+
A data set of 1114 transitions was constructed
113 parameters fitted to 1042 transitions (72 transitions rejected)
Reduced RMS = 1.6; Microwave RMS = 1.22 MHz; IR RMS = 0.019 cm-1
RMS of the eight lines measured in the present work: 0.273 MHz
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Terahertz spectroscopy of the ground state of methylamine (CH3NH2)
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Introduction to CH3NH2
Torsional motion of CH3
Wagging motion of NH2
Woon, 2007
Barrier heights
536 cm-1
1366 cm-1
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Previous work on the ground state of CH3NH2
~700 lines in 3-470 GHz with uncertainties of 20–500 kHz
~1200 lines in 6-140 cm-1with uncertainties of 0.0007–0.001 cm-1
Hershberger and Turkevich (1947): first microwave spectrum
The Shimoda, Nishikawa and Itoh group (1954, 1956, 1957)
The Lide group (1952, 1953, 1954, 1957)
Ohashi et al (1987): far-infrared transitions
Kreglewski and Wlodarczak (1992)
Kreglewski et al (1992)
Ilyushin et al (2005)
Ilyushin and Lovas (2007)
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Our interest in CH3NH2
CH3NH2 exists in the simulated atmosphere of Titan (Drouin, 2006)
• CH3NH2 observed in the interstellar medium (Fourikis et al. 1974; Kaifu et al. 1974)
CH3NH2: G12 symmetry
Isoelectronic to CH3OH2+
Comprehensive experimental data available
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Observed CH3NH2 spectrum
390-464 GHz
770-859 GHz
876-901 GHz
1061-1198 GHz
1575-1625 GHz
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Energy levels of CH3NH2: G12 group
Ohashi and Hougen, 1987
B2
B1
A2
A1
Selections rules:
A1 A2; B1 B2
E1 E1; E2 E2 (+1 +1; -1 -1; +1 -1)0 A1
A2 1
2 B1
B2 3
E1 4
5
E1+1E1-1
E2 6
7
E2+1E2-1
J, K = Ka
J, K = Ka
J, K, ′
Near-prolate asymmetric top
J, K = Ka
SPFIT
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Hamiltonian model for CH3NH2 (I)
Ohashi et al, 1987
Hamiltonian matrix elements are expanded in Fourier series
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Hamiltonian model for CH3NH2 (II)
Ohashi et al, 1987
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Hamiltonian model for CH3NH2 (III)
K = ±2 term
Ohashi et al, 1987
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Hamiltonian model for CH3NH2 (IV)
K = ±1 term
Ohashi et al, 1987
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SPFIT operators
A1 A2 B1 B2 E1+1 E1-1 E2+1 E2-1 coscos cos –cos –cos coscos(/3)+sinsin(/3) coscos(2/3)+sinsin(2/3)
= 2
"'
3
2 KK
2 2 1000000000 -3.0984147127856E+003 1.000000E+037 h2v A1 3 2 -1000000011 -3.0984147127856E+003 1.000000 A2 4 2 -1000000022 3.0984147127856E+003 -1.000000 B1 5 2 -1000000033 3.0984147127856E+003 -1.000000 B2 6 2 -1000000044 -1.5492073563928E+003 0.500000 E1+1 7 2 -11000000055 -2.6833058527323E+003 0.866025 E1-1 8 2 -1000000066 1.5492073563928E+003 -0.500000 E2+1 9 2 -11000000077 -2.6833058527323E+003 0.866025 E2-1
1: ×cos11: ×sin
Regular operators
SPFIT operators
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Fitting results for CH3NH2
A data set of 2800 transitions was constructed (~900 lines from the present study))
60 parameters fitted to 2500 transitions (300 lines rejected) Reduced RMS = 1.5 Microwave RMS = 0.231 MHzIR RMS = 0.00082 cm-1
Rejected lines are all from K = ±1 transitions with K′ or K″=1
Observed-calculated values range from 0.5 – 1 MHz
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Observed vs. calculated CH3NH2 spectrum
J′=24, K′=5 J″=23, K″=5
A2
A1
B1
B2E2-1
E2-1 E2+1
E2+1
E1-1
E1-1
A1
A2
B2
B1 E1+1
E1+1
1062370 1062450
Nuclear spin weights:
A1:A2:B1:B2:E1+1:E1-1:E2+1:E2-1
4 : 4 :12 :12: 6 : 6 : 2 : 2
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Experiments for interstellar weeds (I)
Weeds1.6 1.1 1.0 0.9 0.8 0.7 0.6 0.4 0.3 THz
1157-1626 1055-1175 970-1050 850-930 770-850 600-700 530-620 390-530 290-320 GHz
CH3OH X X X X X X X X X
CH3OCHO X / X
CH3OCH3 X X X X X
CH3CH2CN X X X X X
SO2 DONE
isotopologues
What are interstellar weeds?Abundant (10-7 relative to H2)
Low-lying vibrational statesDense rotational lines Making observing less abundant species difficult
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Experiments for interstellar weeds (II)Species 1.6 1.1 1.0 0.9 0.8 0.7 0.6 0.4 0.3 THz
1157-1626 1055-1175 970-1050 850-930 770-850 600-700 530-620 390-530 290-320 GHz
CH3OD x x
CH318OH x
x
13CH3OH / / / x
CH2DOH x x x x x x x x
13CH3OCHO
CH3O13CHO
CH318OCHO
CH3OCH18O
CH2DOCHO
CH3OCDO
13CH3OCH3
CH2DOCH3
CH318OCH3
13CH3CH2CN
CH313CH2CN
CH3CH213CN
CH3CH2C15N
CH2DCH2CN
CH3CHDCN
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~20 lines/GHz
13CH3OH spectrum around 0.9 THz
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CH3CH2CN spectrum around 0.5 THz
~140 lines/GHz
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Acknowledgements
Drs. Brian Drouin, John Pearson and Herb Pickett
Tim Crawford and William Chun
Alma Cardenas and Rowena Dineros
NPP/ORAU
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H2O 22, 66,1 – 75,2
Work in progress
Global fitting of the X 3g–, a 1g, b 1g
+ and B 3u– states of the six
isotopologues of O2
Terahertz spectroscopy and global analysis of the ground state, 2, 22 and 4 states of NH3
Terahertz spectroscopy and global analysis of the ground state, 22, 1, 3 states of H2O absorption
emission
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Future work
H2 H2+ CH3
+ CH5+ CH4 CH2 3
+ CH2 2 CH3 + CH3 3+ CHm nCH2
+ CH4 + CH4 2+ CH4 3
+CH+H3+C H2 H2 e- e- C+ H2H2 C+ H2 H2 H2h H2
CH3 C4+
e-
H2
C+
CH4CH3 2
e- e-
CH2 HCN3 3+
HCN3 HC N2 +1m
HCNe- e-
CH2 5+
CH2 4
HCO2 3+
CO3
CH3+ CO
e- e-
OH+
HO2 +
HO3 +
HO2OH
O
H2
H2
e-e-
NH2 +
N2
CH
CHCO3+ CHOH3 2
+
CHCO2 CHOH3
HCO,CHOH,CHOCH
2
2 5
3 3
COHO2CHOH,3
e-e-
e- e-
CHCNH2 5+
CHCNH3+CHNH3 2
+
HCNH+
HCN
CHNH3 2
CHNH,2 CHCN3
CHCN2 5
NNH3 HCN
CHCN3
e-
e- e-
e-
CH+, CH2+, CH3
+, CH2D+, etc.
H2D+, HD2+
HD2O+, H2DO+
H2O+
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Application of our results to astrophysics (I)
Our model prediction for CO(CH2OH)2 (DAH) transitions at 300K
Submillimeter Array observations at 330 GHz towards G19.6
330390.425 GHz
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Application of our results to astrophysics (II)
Our model prediction for CO(CH2OH)2 (DAH) transitions at 300K
Submillimeter Array observations at 340 GHz towards G19.6