ABIOTIC FORMATION OF CARBOXYLIC ACIDS (RCOOH) IN INTERSTELLAR AND SOLAR SYSTEM MODEL ICES
The present laboratory study simulated the abiotic formation of carboxylic acids (RCOOH) in interstellar and solar system model ices of carbon dioxide (CO{sub 2})-hydrocarbon mix C{sub n} H{sub 2n+2} (n = 1-6). The pristine model ices were irradiated at 10 K under contamination-free, ultrahigh vacuum conditions with energetic electrons generated in the track of galactic cosmic-ray particles. The chemical processing of the ices was monitored by a Fourier transform infrared spectrometer and a quadrupole mass spectrometer during the irradiation phase and subsequent warm-up phases on line and in situ in order to extract qualitative (carriers) and quantitative (rate constants and yields) information on the newly synthesized species. Carboxylic acids were identified to be the main carrier, together with carbon monoxide (CO) and a trace of formyl (HCO) and hydroxycarbonyl (HOCO) radicals at 10 K. The upper limit of acid column density at 10 K was estimated as much as (1.2 {+-} 0.1) x 10{sup 17} molecules cm{sup -2} at doses of 17 {+-} 2 eV molecule{sup -1}, or the yield of 39% {+-} 4% from the initial column density of carbon dioxide. The temporal column density profiles of the products were then numerically fit using two independent kinetic schemes of reaction mechanisms. Finally, we transfer this laboratory simulation to star-forming regions of the interstellar medium, wherein cosmic-ray-induced processing of icy grains at temperatures as low as 10 K could contribute to the current level of chemical complexity as evidenced in astronomical observations and in extracts of carbonaceous meteorites.
- OSTI ID:
- 21474379
- Journal Information:
- Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 725; ISSN ASJOAB; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON MONOXIDE
CARBON OXIDES
CARBOXYLIC ACIDS
CHALCOGENIDES
COSMIC RADIATION
ELECTRONS
ELEMENTARY PARTICLES
EVOLUTION
FERMIONS
FOURIER TRANSFORM SPECTROMETERS
HYDROCARBONS
ICE
INFRARED SPECTROMETERS
IONIZING RADIATIONS
KINETICS
LEPTONS
MASS SPECTROMETERS
MEASURING INSTRUMENTS
METEORITES
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PLANETS
RADIATIONS
RADICALS
REACTION KINETICS
SATELLITES
SIMULATION
SOLAR SYSTEM
SPECTROMETERS
STAR EVOLUTION
STARS
TAIL ELECTRONS