millimeter/submillimeter spectroscopy of prebiotic molecules formed from the o( 1 d) insertion into...
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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