Infrared spectra and band strengths of CH3SH, an interstellar molecule.

Three solid phases of CH3SH (methanethiol or methyl mercaptan) have been prepared and their mid-infrared spectra recorded at 10-110 K, with an emphasis on the 17-100 K region. Refractive indices have been measured at two temperatures and used to estimate ice densities and infrared band strengths. Vapor pressures for the two crystalline phases of CH3SH at 110 K are estimated. The behavior of amorphous CH3SH on warming is presented and discussed in terms of Ostwald's step rule. Comparisons to CH3OH under similar conditions are made, and some inconsistencies and ambiguities in the CH3SH literature are examined and corrected.