EXCITED-STATE POTENTIAL-ENERGY CURVES FROM TIME-DEPENDENT DENSITY-FUNCTIONAL THEORY - A CROSS-SECTION OF FORMALDEHYDES (1)A(1) MANIFOLD

This work reports the first density-functional theory (DFT) treatment of excited-state potential energy surfaces exhibiting avoided crossing s. Time-dependent DET (TD-DFT) results, using a recently proposed asym ptotically corrected local density approximation functional, are compa red with multireference doubles configuration interaction (MRD-CI) res ults for the (1)A(1) manifold of the CO stretching curves of planar fo rmaldehyde. TD-DFT is found to reproduce the qualitative features esse ntial for understanding the spectroscopy of this manifold, specificall y the strong mixing of the (1)(pi, pi) With Rydberg transitions and t he resultant avoided crossings. (C) 1998 John Wiley & Sons, Inc.