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Astron. Astrophys. 328, 419-425 (1997)

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Is SiS2 the carrier of the unidentified 21 micron emission feature?

G.F. Kraus 1, J.A. Nuth III 2 and R.N. Nelson 3

1 Physical Science Department, Charles County Community College, LaPlata, MD 20646, USA
2 Astrochemistry Branch, Code 691, NASA/GSFC, Greenbelt, MD 20771, USA
3 Chemistry Department, Georgia Southern University, Statesboro, GA 30460, USA

Received 23 February 1997 / Accepted 4 March 1997

Abstract

Spectra are presented of [FORMULA] samples in a variety of crystal forms taken at both room temperature and at 600 K over the wavelength range from 5-25 microns. All spectra show strong features at 22.5 and 9.5 microns as well as less intense bands at 7.5, 8.5, and 12.5 microns. All room temperature spectra also show a feature at 10.7 microns that disappears on heating. One form of [FORMULA] shows strong correlated absorption features at 20 and 17 microns that are rapidly quenched by exposure to humid air with no significant change to the 7-13 and 22 micron features also present in the sample. These [FORMULA] spectra are consistent with previous spectra obtained by Nuth et al. (1985), are marginally consistent with the identification of [FORMULA] as the source of the observed 21 micron peak in several carbon-rich stellar sources, and suggest additional observations of these stellar sources that might confirm or refute the presence of [FORMULA]. Specifically, if no feature at 17 microns is detected in objects that display the strong 21 micron emission feature then [FORMULA] should be ruled out as a candidate for this band.

Key words: line: identifications – stars: circumstellar matter – ISM: dust – infrared: lines and bands – methods: laboratory

Send offprint requests to: J.A. Nuth III

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© European Southern Observatory (ESO) 1997

Online publication: March 24, 1998

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