Kurt M. Christoffel

Investigations of self-consistent field, scf ci and virtual stateconfiguration interaction vibrational energies for a model three-mode system

Abstract Self-consistent field vibrational energy eigenvalues are reported for a model three-mode system considered previously by Noid et al. These eigenvalues and those from configuration interaction calculations based on true SCF wavefunctions and virtual state wavefunctions are compared with the previous semiclassical and exact quantum ones of Noid et al.

Complex coordinate calculations of Feshbach resonance energies and widths for a collinear triatomic system

Complex resonance energies are calculated for a model triatomic system studied previously by Eastes and Marcus [W. Eastes and R. A. Marcus, J. Chem. Phys. 59, 4757 (1973)]. The complex coordinate method is employed to obtain resonance positions and widths for six states. The positions are all in excellent agreement with previous scattering and stabilization results and there is also good agreement with the one width obtained previously from scattering calculations. The additional widths obtained are given for the first time. Some speculations about possible laser induced absorption and emission among these resonances and true bound states are made.

Quantum and classical dynamics of a coupled double well oscillator

We consider the effect of coupling in a model, two mathematical dimension isomerization reaction. The isomerization is described by a symmetric double well potential and the other degree of freedom is a harmonic bond. The time evolution of the reaction is studied in detail by a variety of quantum and classical mechanical methods. We consider first and second order quantum perturbation theory, self‐consistent field theory, self‐consistent field‐configuration interaction theory, and vibrationally adiabatic theory. Classically, we consider exact trajectories and approximate ones based on a quantized vibrationally adiabatic theory. The effect of vibrational excitation of the harmonic degree of freedom on the isomerization rate is investigated as is the extent to which quantum and classical descriptions of this effect differ. We point out two quantum effects in this model system and note that one is due to the coupling between the two degrees of freedom. This effect has not been previously reported; however, i...

Three reaction pathways in the H + HCO --> H2 + CO reaction.

We report quasiclassical trajectory calculations of the H + HCO --> H(2) + CO reaction using a recent global potential energy surface. Three microscopic pathways are identified for this reaction. One is a direct abstraction, and the others both proceed via initial formation of a long-lived complex in the H(2)CO well followed by reaction (a) over the molecular saddle point transition state or (b) via a roaming pathway previously identified for the unimolecular photodissociation reaction [Townsend et al., Science 2004, 306, 1158]. Cross sections and product internal energy distributions for each pathway are calculated for five initial collision energies.

Complex coordinate, self‐consistent field calculations of vibrational resonance energies

Application of the complex coordinate rotation method to molecular vibrational resonances is made at the self‐consistent field (SCF) level. The highly coupled, two‐mode, model system of Waite and Miller [B.A. Waite and W. H. Miller, J. Chem. Phys. 73, 3713 (1980)] is used to test the accuracy of the complex coordinate SCF method. A substantial improvement over the zero‐order results is found.