## Examination of the 2 /sup 1/A/sub 1/ states of formaldehyde and ketene including analytic configuration interaction energy first derivatives for singlet excited electronic states of the same symmetry as the ground state

In an accompanying paper by Lee, Allen, and Schaefer (J. Chem. Phys. 87, xxxx (1987)), an efficient formulation for the analytic evaluation of two-configuration self-consistent-field configuration interaction (TCSCF-CI) energy first derivatives is presented. In this paper the TCSCF-CI gradient method is adapted and applied to singlet excited electronic states of the same symmetry as the ground state. Since single-configuration self-consistent-field configuration interaction (SCF-CI) wave functions are unreliable for such electronic states due to the possibility of variational collapse, the TCSCF-CI method based on excited-state orbitals is the simplest means by which dynamical electron correlation can be incorporated effectively. Geometrical structures,more »