Infrared spectra, rotational correlation functions, band moments, and intermolecular mean squared torques of methane dissolved in liquid noble gases

Extensive measurements of the infrared (i.r.) absorption spectra of liquid methane and of methane dissolved in liquid argon, krypton, and xenon have been carried out. Band profiles for the v 3 and v 4 modes of CH 4 and CD 4 are reported. From these profiles the rotational correlation functions have been calculated. Comparison of the experimental functions with the functions calculated for the free rotators at the appropriate temperatures reveals that each molecule rotates freely for only 1.3 × 10 −13 s before it undergoes a hard collision; the same result was obtained for all the systems investigated. Difficulties in obtaining accurate values of the band moments are discussed and suggestions for overcoming them are presented. Values ranging from 6.9 to 8.2 × 10 4 cm −2 have been obtained for the mean squared torques acting on methane in the various solutions.