CALCULATION OF CENTRIFUGAL DISTORTION CONSTANTS AND INERTIA DEFECTS OF H2S D2S H2SE AND D2SE INTRODUCING INFLUENCE OF ANHARMONICITY

Several of the harmonic frequencies of these molecules have been empirically determined to two decimal places in cm-1. These, together with the rest estimated by other authors to the same degree of accuracy, have been used to evaluate quadratic potential constants in the most general force field. In relation to this, a comparison is given between accuracies of some prevailing methods of estimating harmonic frequencies for the bent XH2 and XD2 molecules. It has been confirmed that the Dennison's isotopic rule, which states that the anharmonic correction is proportional to the harmonic frequency, supplies a simple and efficient method when combined with the Wilson's splitting of high frequencies from low for vibration calculation. This method increases its accuracy rapidly with increasing mass of the central atom. The calculated harmonic frequencies and potential constants have enabled evaluation of the centrifugal distortion constants and inertia defects. A major part of the hitherto involved uncertainties, which are due to partial or complete neglect of anharmonicities, seems to have been removed by the present work. The obtained centrifugal stretching constants in the ground state are as follows (Mcps): {A table is presented} The calculated inertia defects are in good agreement with experiments. © 1969.