PARTIALLY COUPLED ELECTRICAL MODEL OF VIBRATIONAL FREQUENCY-SHIFTS INWEAK ATOM DIATOMIC AND DIATOMIC DIATOMIC COMPLEXES

A simple model has been found to account for the blue and red shifts i n the stretching transition frequencies of diatomic molecules that occ ur because of weak bonding to rare-gas atoms or to other diatomics. Th e primary element in the model is that of electrical interaction betwe en the interacting species. This affects transition frequencies becaus e the electrical properties change upon vibrational excitation. A seco nd important element is the coupling of the intramolecular stretch to the weak mode vibrations. This comes about because of a change in the shape of the potential surface upon excitation of the diatomic and bec ause of the change in the on-average bond length of the diatomic. Calc ulations with this model were carried out for a number of complexes, a nd comparison with 19 available experimental values indicates that shi fts are predicted with a mean error of 10 cm-1, excluding one interest ing anomalous case, the HF frequency shift in OC-HF. The model is appl icable in cases of both blue and red shifts.