Methanol Photodissociation and its Role in the Complex Chemistry of the Interstellar...
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Methanol Photodissociation and its Role in the Complex Chemistry of the Interstellar Medium Jacob C. Laas † , Mary L. Radhuber † , Robin T. Garrod, ‡ and Susanna L. Widicus Weaver † † Department of Chemistry, Emory University, Atlanta, GA 30322 ‡ Department of Astronomy, Cornell University, Ithaca, NY 14853 Final Abundances for High-Mass Hot Core Chemical Abundances During Hot Core Warm-Up Objectives • Accurately determine methanol photolysis branching ratios using molecular spectroscopy • Use astrochemical models to study effects of photolysis branching ratios on complex interstellar chemistry Motivation • Methanol photolysis branching ratios are largely unmeasured, but are thought to play a major role in complex interstellar chemistry: CH 3 OH CH 2 OH + H CH 3 O + H CH 3 + OH CH 2 O + H 2 CH 2 + H 2 O HCOH + H 2 hν Highly reactive radicals! HCO glycolaldehyde methyl formate acetaldehyde Methanol Photolysis • Methanol photolysis is efficient at many wavelengths from 120-200 nm; branching ratios change with wavelength • THz spectroscopy is being used for quantitative monitoring of gas-phase photolysis products Astrochemical Modeling • Ice composition was set to match observations and earlier model 1 • Branching ratios of three primary methanol photolysis product channels were adjusted • Two-stage physical model involving collapse and gradual warm- up was used • Molecular abundances were monitored as a function of time References 1 Robin T. Garrod, Susanna L. Widicus Weaver, & Eric Herbst 2008, Ap. J., 682, 283-302. Acknowledgements Eric Herbst, Thomas Orlando, & Michael Heaven Results & Future Work • Photolysis branching ratios influence relative abundances of structural isomers and formation of complex organic molecules • Branching ratios with CH 3 at 90% gave best match to Sgr • Quantitative gas-phase measurements of branching ratios are needed to guide future models • Wavelength dependence of photolysis should also be determined and incorporated into models • Future collaboration with Orlando group at GA Tech planned for condensed-phase measurements
Transcript of Methanol Photodissociation and its Role in the Complex Chemistry of the Interstellar...
Methanol Photodissociation and its Role in the
Complex Chemistry of the Interstellar MediumJacob C. Laas†, Mary L. Radhuber†, Robin T. Garrod,‡ and Susanna L. Widicus Weaver†
†Department of Chemistry, Emory University, Atlanta, GA 30322‡Department of Astronomy, Cornell University, Ithaca, NY 14853
Final Abundances for High-Mass Hot Core
Chemical Abundances During Hot Core Warm-Up
Objectives• Accurately determine methanol photolysis
branching ratios using molecular spectroscopy
• Use astrochemical models to study effects of
photolysis branching ratios on complex
interstellar chemistry
Motivation• Methanol photolysis branching ratios are
largely unmeasured, but are thought to play a
major role in complex interstellar chemistry:
CH3OH CH2OH + H
CH3O + H
CH3 + OH
CH2O + H2
CH2 + H2O
HCOH + H2
hν
Highly reactive radicals!
HCOglycolaldehyde
methyl formate
acetaldehyde
Methanol Photolysis• Methanol photolysis is efficient at many
wavelengths from 120-200 nm; branching
ratios change with wavelength
• THz spectroscopy is being used for
quantitative monitoring of gas-phase
photolysis products
Astrochemical Modeling• Ice composition was set to match observations and earlier model1
• Branching ratios of three primary methanol photolysis product
channels were adjusted
• Two-stage physical model involving collapse and gradual warm-
up was used
• Molecular abundances were monitored as a function of time
References1 Robin T. Garrod, Susanna L. Widicus Weaver, & Eric Herbst 2008, Ap. J., 682, 283-302.
AcknowledgementsEric Herbst, Thomas Orlando, & Michael Heaven
Results & Future Work• Photolysis branching ratios influence relative abundances of
structural isomers and formation of complex organic molecules
• Branching ratios with CH3 at 90% gave best match to Sgr
• Quantitative gas-phase measurements of branching ratios are
needed to guide future models
• Wavelength dependence of photolysis should also be determined
and incorporated into models
• Future collaboration with Orlando group at GA Tech planned for
condensed-phase measurements
