Gert Due Billing

Vibrational relaxation of oxygen. State to state rate constants

Abstract A semi-classical collision model has been used to calculate V-V (vibration—vibration) and V—T/R (vibration—translation/rotation) rate constants for vibrational transitions in oxygen. The potential energy surface is obtained from a recent atom—atom fit to ab initio data. In the semi-classical model used the translational and rotational motion of the two molecules is treated classically whereas the vibrational motion of both molecules is quantized.

On a semiclassical approach to energy transfer by atom/molecule-surface collisions

Abstract A semiclassical theory for energy transfer in polyatomic molecules has been extended to atom/molecule-surface scattering problems. The solid is treated

Classical path method in inelastic and reactive scattering

Abstract The semiclassical (classical path) method has over the years probably been the most commonly used approximate method for describing many molecular dynamical processes in inelastic, non-adiabatic and recently also in reactive scattering. Here an overview of the development of the theory is given. Its connection to various other approximate dynamic theories such as the eikonal, time-dependent self-consistent field, Gaussian wave packet and the Feynmann path theory is discussed. Various numerical and technical schemes for solving the mixed quantum-classical equations through algebraic, state and grid expansion methods are also given.

On the applicability of the classical trajectory equations in inelastic scattering theory

Abstract By using the classical trajectory equations and an average trajectory we have been able to predict the single quantum transitions for the one-dimensional atom—diatom collision problem to within 10–30%. The double quantum transitions P 02 are correct to within at least a factor of two.

Quantum corrections to the classical path theory

We discuss an effective numerical method for obtaining the best trajectory to be used in the classical path approach. The method is based upon a time dependent variational method, which yields from first principles the classical path equations. In its simplest formulation the classical path equations contain an optimal momentum determined self‐consistently. A variational method, which satisfies detailed balance is also discussed.

Theory of V–V and V–T/R energy transfer for HF (n=1 to 7)+HF (0)

Rate constants for vibrational relaxation of HF in vibrational states n=1 to 7 are calculated semiclassically for HF(n)+HF. The variation with n agrees well with experiment. The absolute values are about 55% of the experimental results. Orbiting collisions are important. The relaxation mechanism found disagrees with three well‐known more approximate theories. V–T/R transfer is found to be important especially for the higher levels. A renormalization procedure is suggested as a remedy for the well‐known numerical inaccuracy of trajectories with very long‐lived collision complexes. This renormalization was not important for the present work.

Semiclassical calculation of VV and VT rate coeffecients in CO

Abstract We have calculated 66 rate constants for vibration-vibration (V-V) and vibration-translation/rotation (V-T/R) energy transfer in CO by using a semiclassical collision model. Extensive comparison with experimental data and more approximate theoretical predictions is carried out.

The Role of Degenerate States in Chemistry

Early Perspectives on Geometric Phase (M. S. Child).The Electronic Non-Adiabatic Coupling Term in Molecular Systems: A Theoretical Approach (By Michael Baer).Non-Adiabatic Effects in Chemical Reactions: Extended Born-Oppenheimer Equations and Its Applications (Satrajit Adhikari and Gert Due Billing).Complex States of Simple Molecular Systems (R. Englman and A. Yahalom).Quantum Reaction Dynamics for Multiple Electronic States (Aron Kuppermann and Ravinder Abrol).Electron Nuclear Dynamics (Yngve Ohrn and Erik Deumens).Applying Direct Molecular Dynamics to Non-Adiabatic Systems (G. A. Worth and M. A. Robb).Conical Intersections in Molecular Photochemistry: The Phase-Change Approach (Yehuda Haas and Shmuel Zilberg).The Crude Born-Oppenheimer Adiabatic Approximation of Molecular Potential Energies (K. K. Liang, J. C. Jiang, V. V. Kislov, A. M. Mebel, and S. H. Lin).Conical Intersections and the Spin-Orbit Interaction (Spiridoula Matsika and David R. Yarkony).Renner-Teller Effect and Spin-Orbit Coupling in Triatomic and Tetraatomic Molecules (Miljenko Peric- and Sigrid D. Peyerimhoff).Permutational Symmetry and the Role of Nuclear Spin in the Vibrational Spectra of Molecules in Doubly Degenerate Electronic States: The Trimers of 2S Atoms (J. C. Varandas and Z. R. Xu).Author Index.Subject Index.

Hydrogen atom recombination on graphite at 10 K via the Eley–Rideal mechanism

Abstract This work reports results on the recombination of hydrogen atoms on a graphite surface at 10 K obtained using a detailed semi-classical molecular dynamics method in connection with the use of recently proposed ab initio potential energy surfaces. The calculated recombination probabilities together with the vibrational distributions of the formed H 2 molecules obtained assuming that the surface reaction proceeds via the Eley–Rideal mechanism can have an impact on the chemistry of H 2 formation in interstellar space.

Temperature dependence of HF vibrational relaxation

Semiclassical calculations of rate constants for energy transfer in an HF gas from 300 to 3500 K are reported. The potential hypersurface used was an analytic fit to recent SCF calculations plus the experimental dispersion potential. Good agreement with experiments was obtained without further adjustment of the potential parameters.