The SiH Vibrational Stretch as an Indicator of the Chemical State of Interstellar Grains
Abstract
The infrared spectra of amorphous silicate grains and films formed in a variety of laboratory experiments have been measured. It is found that the frequency of the SiH fundamental stretch is extremely sensitive to the chemical environment of the grain in which the silicon is bound and varies from 2270/cm in oxidized grains to 2110/cm in a reducing environment. It is proposed that features previously observed in W33A could be due to -SiH groups in amorphous silica, partially reduced silica, silicon nitride or slightly oxidized silicon carbide. It is predicted that observations at 2270/cm will reveal a feature due to -SiH groups in highly oxidized interstelar and circumstellar grains. Such a feature might also appear in the spectra of comets.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 1991
- DOI:
- 10.1086/186044
- Bibcode:
- 1991ApJ...373L..31M
- Keywords:
-
- Interstellar Chemistry;
- Interstellar Matter;
- Metal Hydrides;
- Silicates;
- Astronomical Spectroscopy;
- Cosmic Dust;
- Infrared Spectra;
- Stellar Envelopes;
- Atomic and Molecular Physics;
- INFRARED: SPECTRA;
- INTERSTELLAR: GRAINS;
- LABORATORY SPECTRA;
- LINE IDENTIFICATIONS;
- MOLECULAR PROCESSES;
- STARS: CIRCUMSTELLAR SHELLS