Intermolecular Potentials and Infrared Spectra

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Abstract
In an effort to learn more about the angle dependence of intermolecular potentials, pressure broadened infrared spectra have been compared with calculations from a trial potential. Infrared spectra of the CO fundamental absorption band were measured at densities of helium gas perturber from 10 to 100 amagats at room temperature. The same spectra were calculated from the potential using a semiclassical impact theory of overlapping lines. The comparisons show that the potential accounts quite well for the spectra except at low pressures, suggesting that the long‐range part of the potential was too strong. Satisfactory agreement was obtained even at pressures which were so high that the impact theory is not rigorously applicable. The success of these calculations should encourage the use of this technique for, on the one hand, testing intermolecular potentials and, on the other, predicting pressure broadened spectra of molecular gases over a wide range of pressures.