Vibrational anharmonicity in CF4

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Abstract
A simple anharmonic force field, consisting of a general quadratic force field in curvilinear coordinates, augmented with principal cubic and quartic valence‐bond stretching force constants based on a Morse function, has been determined by least‐squares adjustment to the vibrational energies of CF4. Since this model did not give a value of the cubic normal‐coordinate force constant k344 in agreement with experiment, we considered a second force field identical to the first one except for the introduction of cubic stretch–bend–bend interaction force constants. These force fields have been used to calculate the tetrahedral anharmonic splittings of overtone and combination levels of CF4 and the calculated splittings have been compared with observed values determined by re‐examining the previously published infrared spectra of CF4 in liquid–argon solution.