MULTIPHOTON ABSORPTION STRENGTHS FROM SIMPLE AB INITI WAVEFUNCTIONS

Abstract

We are pursuing simple methods for predicting the multiphoton absorption strengths of relevance to REMPI spectroscopy. The usual perturbation expressions are valid when there are no intermediate near-resonances. In the present study, vibrational and rotational structure are ignored to simplify the calculation further. Within this approximation, only electronic energy levels and electric dipole matrix elements are needed. One-color, two-photon and three-photon absorption strengths will be presented, based upon simple singles-only configuration interaction (CIS) wavefunctions. Comparisons with experimental results will be made where possible. Convergence behavior will also be discussed, both with respect to the one-electron basis set and the number of intermediate states in the perturbation expansion.