Spectroscopy in Liquid‐Rare‐Gas Solvents. Infrared Spectra of CH_4 in Argon and of HCl in Xenon

Abstract

A low‐temperature cell employing barium fluoride windows and indium metal gaskets has been built and is being used for the study of rotational, vibrational, and electronic motions of molecules in liquid rare gases. The ν_3 fundamental of CH_4 in liquid argon shows a single, relatively sharp Q branch. The P and R branches are probably present but apparently are lost in the wings of the Q branch. The infrared spectrum near 3.5 μ of HCl in liquid xenon shows well‐resolved P, Q, and R branches, but the individual rotational lines are not resolved. The O branch is not resolved from the tail of the P branch, but there is some indication of the S branch on the high‐frequency side of the spectrum. The Q branch is shifted 36 cm^(-1) to the low‐frequency side of its gas‐phase position. The appearance of O, Q, and S branches is expected because of the presence of an induced dipole moment through the polarizability of the solvent. The agreement between the observed spectrum and that anticipated on the basis of nearly free rotation gives good evidence for the existence of quantized rotational motions of HCl in liquid xenon.

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