Initio Multiconfiguration Self-consistent Field Research Articles

A theoretical investigation of the UV spectrum of ethyl radical

A b initio multiconfiguration self-consistent field and configuration interaction calculations show that the ethyl radical when vertically excited from its ground state to the lowest 3p Rydberg state dissociates without a barrier to ground state methyl radical and 1B1 methylene, which accounts for the continuous nature of the ethyl spectrum. It is also shown that the 3p Rydberg states of ethyl are lower in energy in the nonclassical (hydrogen bridged) equilibrium structure of the ethyl cation than in the classical ground state ethyl radical equilibrium structure or at their respective adiabatic dissociation limits. This suggests the equilibrium structures of the 3p Rydberg states are nonclassical.

Formaldehyde: A b i n i t i o MCSCF+CI transition state for H2CO → CO+H2 on the S surface

A b initio multiconfiguration self-consistent field (MCSCF) and configuration interaction (CI) calculations have yielded an activation energy of 80.9±3.0 kcal/mol for the dissociation of formaldehyde to H2 and CO on the ground state potential energy surface. The error limits are estimates based on an analysis of the effects of one-particle basis set, electron correlation, and transition state structure on the activation energy. Accurate structures and harmonic frequencies are presented for H2CO (X 1A1) and the transition state.