OPTICAL PROPERTIES OF GLASSY SiS_2 AND THE 21 MICRON FEATURE

摘要

We present optical constants for glassy SiS_2 in the infrared that are of relevance for the hitherto unidentified 21 μm feature observed in the spectra of proto-planetary nebulae. Preparation and infrared spectroscopy were performed under inert conditions to prevent an oxidation of the samples. The laboratory spectra show a strong band at about 20 μm and a band of medium strength at 16.5 μm. Calculations with these data indicate that cool small SiS_2 particles allow a satisfactory representation of the observed 21 μm band. A crucial test of this identification would be the detection of the 16.5 μm band of SiS_2 by Infrared Space Observatory.