EXPANDED LOCAL MODE APPROACH FOR XY(2) (C-2V) MOLECULES

For XY(2) (C-2 nu symmetry) molecules, the local mode method is modifi ed on the basis of a careful analysis of the transformation coefficien ts l(N alpha lambda) and the properties of the intramolecular potentia l function, and an expanded local mode approach is derived. It is show n that relationships between known spectroscopic parameters, found in the spectroscopic literature, can be improved. New relationships betwe en the centrifugal distortion coefficients are obtained. It is shown t hat knowledge of the centrifugal distortion coefficients of the ground vibrational state allows the possibility of predicting values of both the band centres and the spectroscopic parameters of deformational ba nds, even under conditions of a total absence of initial information o n these deformational bands. The prediction possibility of the derived expanded local mode approach is analyzed.