Coupled-cluster calculations of the electronic excitation spectrum of free base porphin in a polarized basis

Similarity transformed equation-of-motion coupled-cluster calculations on the excited states of free base porphin are reported. These are the first calculations to use polarization functions for all of the excited states, and the polarization functions are found to be very important for accurately describing the optically allowed states. These calculations strongly support the traditional interpretation of the electronic spectrum of free base porphin. (C) 1998 American Institute of Physics.