Millimeter/Submillimeter Spectroscopy of Prebiotic Molecules Formed from the O(1D)

Insertion Into Methylamine

Brian Hays, Althea Roy,

and Susanna Widicus Weaver

Emory University

H2O + hn OH + HH2 + O

CH3OH + hn CH3 + OHCH3O + HCH2OH + H

NH3 + hn NH2 + H

hn

H2O, CO, CH3OH, NH3 , H2CO Ice mantle

Complex Chemistry in the ISM

Garrod, Widicus Weaver, & Herbst, 2008Charnley, 2001

H2O + hn OH + HH2 + O

CH3OH + hn CH3 + OHCH3O + HCH2OH + H

NH3 + hn NH2 + H

CH2OH + NH2 HOCH2NH2

Aminomethanol

hn

H2O, CO, CH3OH, NH3 , H2CO Ice mantle

Complex Chemistry in the ISM

Garrod, Widicus Weaver, & Herbst, 2008Charnley, 2001

H2O + hn OH + HH2 + O

CH3OH + hn CH3 + OHCH3O + HCH2OH + H

NH3 + hn NH2 + H

hn

H2O, CO, CH3OH, NH3 , H2CO Ice mantle

Complex Chemistry in the ISM

aminomethanol glycine protonatedaminomethanol

HCOOH

or H3+

CH3OH2+

-H2O C

C

OO

H

NHH H

H

C

OH

NHH H

HC

OH H

NHH H

H

+

CH2OH + NH2 HOCH2NH2

Aminomethanol

Garrod, Widicus Weaver, & Herbst, 2008Charnley, 2001

Proposed Formation Route for Laboratory Spectroscopy

• Molecules reactive under terrestrial conditions so no laboratory spectra exist

Proposed Formation Route for Laboratory Spectroscopy

• Molecules reactive under terrestrial conditions so no laboratory spectra exist

• Molecules can be produced using barrierless O(1D) insertion reactions

• O(1D) primarily inserts into bonds that are H-X where X=C, N, O, H

1.968 eV energy

E

O(1D)

O(3P)

O(1D) Insertion Into Methane

Chang and Lin, Chem. Phys. Lett. 363 (2002) 175-181

2H

Gas-Phase O(1D) Insertion Reactions

Microwave Synthesizer

Millimeter/SubmillimeterFrequency Multiplier

50 GHz – 1.2 THz

Hot Electron Bolometer

Excimer Laser

Pulsed Valve + Fused Silica Capillary

O3 + hν (248 nm) O2(1Δ) + O(1D)

O(1D) + Precursor Product

Oscilloscope

Supersonic Expansion

Ar, CH4, O2, O3

Ozone Depletion O3 + hν (248 nm) O2(1Δ) + O(1D)

Methanol ProductionO(1D) + CH4

CH3OH

_

Methanol from O(1D) Insertion

• First detection of O(1D) insertion products with a supersonic expansion

• First millimeter/submillimeter spectrometer that probes laser-induced bimolecular reaction products in a supersonic expansion

• Also detected: H2CO, HO2, CH3O

Methylamine Reaction

Hays & Widicus Weaver 2013, JPCA, 117, 7142

CCSD(T)//MP2/aug-cc-pVTZ

Methylamine Reaction

CH3NH2 + O3 ?????• Significant dark

reactions behind pulsed valve

• Reduces ozone concentration before photolysis

• Chokes valve

Methylamine Reaction

• Gases are mixed immediately before the photolysis region

• Dark reactions between precursor gases are minimized

• Valves are more stable because side products cannot form in gas line

O3

CH3NH2

CH3NH2 + O3 ?????

Methylamine ReactionO(1D) + CH3NH2 products

Laser RFIDepletion

Methylamine + O(1D) ReactionsCH3NH2 + O(1D) →

HOCH2NH2 (aminomethanol) CH3NHOH (n-methyl hydroxylamine)

CH3ONH2 (aminomethyl ether)Known molecules that have been detected:CH3OH, H2CO, CH3O,

HO2, NO, CH2NH, NH2CHO

HNCO, HCNO, HNOHCN, HNC, HOOH

HONO, H2CN(?)

Possible products requiring other

frequency windows:NH3, H2O, OH

Methylenimine CH2NH

JKa,Kc = 11,0 – 10,1

F=0–1 2–1 1–2F=2–2 1–0 1–1

• Several unknown transitions have been found• Some are close to predicted H2CN transitions

but no previously observed H2CN transitions have been found

• Guided by ab initio calculations

Towards detection of aminomethanol

• Hyperfine splitting indicates an N-containing molecule• Frequency does not match for any known N-containing products• Near calculated ZPE corrected predicted lines, but …

Toward detection of aminomethanol

• Line intensities increase with increased methylamine conc.

• As these lines increase, lines from other secondary products (i.e., formaldehyde, methanol) decrease

• Evidence indicates that these lines arise from a primary insertion product

Toward detection of aminomethanol

• Several more lines detected around several predicted cold aminomethanol transitions that don’t match any catalog spectra

Toward detection of aminomethanol

Conclusions and Future Work• O(1D) insertion reactions are efficient for forming

astrochemical target molecules• Methane experiments demonstrate efficiency of

O(1D) insertion mechanism• Methylamine experiments give a wide variety of

products• Once confirmed, aminomethanol spectra will be

compared with 32 CSO spectral line surveys

Conclusions and Future Work• O(1D) insertion reactions are efficient for forming

astrochemical target molecules• Methane experiments demonstrate efficiency of

O(1D) insertion mechanism• Methylamine experiments give a wide variety of

products• Once confirmed, aminomethanol spectra will be

compared with 32 CSO spectral line surveys Nadine Wehres -RF10, Thursday

afternoon ALMA session

Acknowledgements

• Widicus Weaver group – Nadine Wehres, Jake Laas, Bridget Deprince

• Dr. Michael Heaven for loan of laser and ozone generator

• Sven Thorwirth• Cherry L. Emerson Center

@ Emory for calculations• NSF #CHE-1150492• NASA #NNX11AI07G