Use of the CNDO Method in Spectroscopy. V. Spin—Orbit Coupling

We report here the use of CNDO/S wavefunctions in the calculation of oscillator strengths of singlet—triplet transitions and the corresponding triplet radiative lifetimes induced by spin—orbit coupling. The starting functions for the perturbation calculations are ground and excited state functions including limited configuration interaction. Numerical calculations are carried through for formaldehyde and azulene. The importance of the calculated ${\mathrm{\sigma \to \pi }}^{*}$ states is discussed.