THEORETICAL CONSIDERATION OF SYMMETRY-FORBIDDEN ELECTRONIC $TRANSITIONS^{*}$

Abstract

A theoretical formalism for describing vibronically-induced, symmetry-forbidden, electronic transitions in polyatomic molecules is examined. The electronic transition moment is calculated from its Maclaurin expansion about the equilibrium configuration of the initial state. The terms in the expansion are calculated directly from semi-empirical wavefunctions. Applications is made to $^{1} U$ ($\pi=^{*}$) $\leftarrow$ $S_{o}$ in formaldehyde and in other carbonyl containing molecules.