Equilibrium Nuclear Distance of Molecules

Abstract

A theory is given to compute the shift of equilibrium nuclear distance of molecule in every electronic state from initially assumed value, in terms of electron-vibration interaction. It is applied to the computation of the equilibrium nuclear distances of the ground, the first and the second singlet excited states of a naphthalene molecule. The calculated relative shifts of the equilibrium point of vibration (corresponding roughly to that of nuclear distance) between the ground and the first and the second singlet excited states are, in average, 3.3×10 -2 Å and 7.1×10 -2 Å respectively. The equilibrium nuclear distances of the molecule are also obtained with LCAO-ASMO-INDO-CI method. The shifts of equilibrium nuclear distances by this method between the ground and the first and the second singlet excited states are 0.5×10 -2 Å and 0.8×10 -2 Å respectively. The values calculated by the two methods are in reasonable agreement.