Self-Consistent Molecular Orbital Methods. X. Molecular Orbital Studies of Excited States with Minimal and Extended Basis Sets

Abstract

Molecular orbital theory is applied to the excited states of a group of small molecules. Vertical transition energies are calculated using minimal and extended basis sets both with and without configuration interaction between singly excited states. The separate effects of extending the basis set and including CI are examined, and an evaluation of the over‐all performance at each level is made by comparing calculated results with experimental values. Minimal basis calculations with limited CI are found to describe adequately ${\mathrm{n\to \pi }}^{*}$ transition energies. Although triplet ${\mathrm{\pi \to \pi }}^{*}$ energies are reasonably described at this level, an extended basis set is necessary to obtain even a moderate approximation to singlet ${\mathrm{\pi \to \pi }}^{*}$ energies.