RECENT RESULTS FROM QUASI-CLASSICAL TRAJECTORY COMPUTATIONS OF ELEMENTARY CHEMICAL-REACTIONS

Recent quasi-classical trajectory (QCT) calculations of the dynamics o f some prototypic elementary reactions, from state-resolved differenti al cross-sections (DCS) to thermal rate constants, are reviewed. The r eactions studied are H + H-2, F + H-2, Cl + H-2 and O(D-1) + H-2, for which reliable potential-energy surfaces (PES) are available. The QCT results are analysed in the tight of the most recent quantum mechanica l (QM) calculations and experimental findings. Tn general, QCT integra l, differential reaction cross-sections and rate constants are found t o be in good agreement with their QM and experimental counterparts, in dicating that, for the systems considered, the motion of the nuclei du ring reactive encounters is largely classical and that quantum effects , such as tunnelling, play a relatively minor role in the overall dyna mics. The importance of the zero-point energy of the transition state is highlighted as one of the most important deficiencies of the QC tre atment. The need for precise QC and quantal simulations of the actual laboratory measurements, in order to identify experimental quantum eff ects dearly, is emphasized. Finally, the importance of the calculation and measurement of vector correlations in chemical reactions is stres sed and some examples are presented.