INFRARED-SPECTRA AND STRUCTURE OF SOLID-PHASES OF SULFUR-TRIOXIDE - POSSIBLE IDENTIFICATION OF SOLID SO3 ON IO SURFACE

The IR spectra of solid sulfur trioxide (SO3) have been examined betwe en 20 and 290 K. The spectral features of an amorphous low-temperature deposit and four additional phases (monomeric, gamma, alpha, and beta ) are presented. Two of the emission peaks in the thermal spectrum of Io recorded by the Voyager IRIS instrument are suggested to be possibl y due to solid SO3 mixed with crystalline SO2. (C) 1995 Academic Press , Inc.