VIBRATIONAL SPECTROSCOPIC STUDIES OF $SO_{3}$ IN SOLID STATE

Sulfur trioxide is an interesting molecule for vibrational spectroscopic studies because of its structural complexities in the condensed state. In this investigation sulfur trioxide was prepared by thermal decomposition of anhydrous Ferric sulfate and copper sulfate invacuum ( $\\sim$ $10^{-6}$ torr). The evolved sulfur trioxide along with some sulfur dioxide was condensed on a Cesium Iodide plate at $\\sim$12K in a closed cycle helium cryo-cooler. Detailed analysis of the infrared and Raman spectra of the sample at several temperature between 12K and 300K has enabled us to follow the phase changes in solid sulfur trioxide. Structural aspects of different phases of $SO_{3}$ will be described in this report.