Far-Infrared Spectra of Gas Molecules Trapped in β-Quinol Clathrates

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Abstract
We have studied the far‐infrared spectra of 12 different gases trapped in the cages of β‐quinol clathrates. The data are most extensive for Ar, Kr, Xe, CO, N2, NO, and O2 in the frequency range from 15 to 85 cm−1. In these cases, monatomic and nonpolar diatomic gas molecules show a single absorption line, which we have assigned to translational motion of the molecule within its cage. Polar diatomic molecules show an additional line, which we have assigned to hindered rotation. These lines are an order of magnitude less intense than ordinary electric dipole transitions. The absorptions due to translational motion arise through dipole moments induced by interaction between the gas molecule and the clathrate cage. The frequencies and shapes of the infrared absorptions as a function of temperature from 1.2° to 170°K, as well as the frequencies of hindered rotation for N2 and O2 deduced from other experiments, were used to evaluate the parameters of potential‐well models for these seven gases. The specific heats associated with the enclosed molecules were computed and found to be in excellent agreement with measured specific heats. Spectra of H2, CH4, CH3F, CHF3, and NF3 clathrates and of α‐quinol are also discussed.

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