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.

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

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

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 )

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)

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

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

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)

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)

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

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

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

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

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

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

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

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

Radio frequency discharge cell (under development)

Cell

1.4 MHz 5 kW

10 A100 A

50 CLOADCTUNE

LEXT LANT

Plasma tank circuit

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

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

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)

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)

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)

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 )

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…

Observed C2D2 terahertz transitions

1067920 1067950

251 12C2D2 lines observed

12C2D2 5 – 4

802375 802425

12C2D2 25 – (4+5)

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)

Multistate analysis of C2H2 and C2D2

1100

5454ll VV

Hamiltonian model for C2H2 and C2D2 (I)

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)

Block form of the Hamiltonian model for C2D2

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

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

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:

Herschel

ALMA

(cm2/molecule) of the Pee and Ree branch lines of the 5-4 band of C2H2

SOFIA

Terahertz spectroscopy and global analysis of H3O+

Yu et al., Astrophys. J. Suppl. Ser. 180 (2009) 119-124

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)

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

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

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

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

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…

Observed H3O+ terahertz transitions

11 34

Observed for the first time

8 H3O+ lines observed

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

Block form of the Hamiltonian model for H3O+

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

Terahertz spectroscopy of the ground state of methylamine (CH3NH2)

Introduction to CH3NH2

Torsional motion of CH3

Wagging motion of NH2

Woon, 2007

Barrier heights

536 cm-1

1366 cm-1

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)

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

Observed CH3NH2 spectrum

390-464 GHz

770-859 GHz

876-901 GHz

1061-1198 GHz

1575-1625 GHz

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

Hamiltonian model for CH3NH2 (I)

Ohashi et al, 1987

Hamiltonian matrix elements are expanded in Fourier series

Hamiltonian model for CH3NH2 (II)

Ohashi et al, 1987

Hamiltonian model for CH3NH2 (III)

K = ±2 term

Ohashi et al, 1987

Hamiltonian model for CH3NH2 (IV)

K = ±1 term

Ohashi et al, 1987

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

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

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

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

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                   

~20 lines/GHz

13CH3OH spectrum around 0.9 THz

CH3CH2CN spectrum around 0.5 THz

~140 lines/GHz

Acknowledgements

Drs. Brian Drouin, John Pearson and Herb Pickett

Tim Crawford and William Chun

Alma Cardenas and Rowena Dineros

NPP/ORAU

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

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+

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

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