A method for the calculation of transition moments between electronic states of molecules using a different one‐electron basis set for each state

Abstract

AbstractA state‐specific approach to the calculation of transition moments between molecular electronic states requires that the wavefunction for each state is expanded in its optimum one‐electron basis and that nonorthonormal basis techniques are used for the calculation of the transition moment integrals. A method has been developed for carrying out such nonorthonormal basis calculations, based on the corresponding orbitals transformation and appropriately defined density matrices, which may be used with configuration interaction (CI) wavefunctions. Further improvements of the method have resulted in a decrease in the time required for the calculations and thus allow its application with moderately large CI expansions for each state. Nonorthonormal basis calculations on transition moments in H2O have been carried out using the above method. The results are in agreement with those of large MRD‐CI calculations.