The Influence of Temperature and State on Infrared Absorption Spectra: Methyl Iodide

The spectra of methyl iodide were determined in the range 2 to 15 microns for the vapor at 25°C, the liquid at 25° and −50°C, and the solid at −78°, −196°, and −269°C. Differences were observed in frequencies, intensities, and band shapes resulting from changes in state and temperature. There is band narrowing with reduction in temperature even in the solid. At the lowest temperatures, band splitting could be resolved in the degenerate bands as well as in the 1252 cm−1 nondegenerate fundamental. Several additional assignments are offered.