Solid organic residues produced by irradiation of hydrocarbon-containing H 2O and H 2O/NH 3 ices: Infrared spectroscopy and astronomical implications
Abstract
Methane clathrate (CH 4· nH 2O) - expected in cometary nuclei, in outer Solar System satellites, and perhaps in interstellar grains—aas well as ices prepared from other combinations of CH 4, C 2H 6, or C 2H 2 with H 2O (and sometimes with NH 3) were irradiated at 77°K by plasma discharge. CH 4 clathrate and other H 2O/hydrocarbon ices color and darken noticeably after a dose ≈10 8 to ≈10 9 erg cm -2 over a period of 1-10 hr. Upon evaporation of the now yellowish to tan irradiated ices, a colored solid film adheres to the walls of the reaction vessel at room temperature. Transmission measurements of these organic films were made from 2.5 to 5μm wavelength. The residue left after CH 4. irradiation exhibits IR bands which we tabulate and identify with alkane, aldehyde, alcohol, and perhaps alkene and substituted aromatic functional groups. Aldehydes are especially well indicated, and may be related to recent claims of polyoxymethylene in the coma of Comet Halley. Spectra presented here are compared with previous studies of UV or proton-irradiated, nonenclathrated hydrocarbon-containing ices and may be useful for interpreting infrared features found in the spectra of comets and interstellar grains.
- Publication:
-
Icarus
- Pub Date:
- June 1989
- DOI:
- 10.1016/0019-1035(89)90082-1
- Bibcode:
- 1989Icar...79..350K
- Keywords:
-
- Ammonia;
- Comet Nuclei;
- Interstellar Matter;
- Irradiation;
- Organic Compounds;
- Water;
- Absorption Spectra;
- Hydrocarbons;
- Ice;
- Infrared Spectra;
- Satellites;
- Spectrum Analysis;
- PLANETS;
- ORGANIC MATERIAL;
- RESIDUE;
- IRRADIATION;
- HYDROCARBONS;
- AMMONIA;
- WATER;
- ICE;
- INFRARED;
- WAVELENGTHS;
- SPECTROSCOPY;
- FORMATION;
- DIAGRAMS;
- ORIGIN;
- LABORATORY STUDIES;
- METHANE;
- CLATHRATES;
- PROCEDURE;
- EXPERIMENTS;
- ALDEHYDES;
- SPECTRA;
- COMPARISONS