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The thermal rate constant for the F + H2 reaction has been derived from the time integral of the flux-flux autocorrelation function. The contribution to the rate for total angular momentum J > 0 was treated both exactly and also by J-shifting and principal axis helicity-conserving approximations. The results obtained show good agreement with the experimental results obtained by Wurzberg et al at T = 300 K. However, it is expected that inclusion of the spin-orbit coupling in the potential energy surface will raise the effective classical barrier height by O.3 to 0.4 kcal/mol.

The association constants and their relations to the thermodynamic activation parameter were evaluated through studies of semiempirical model. It was observed that the free energy of activation of deltaG was linear with temperature. This suggested that the two parameters, free energy activation and the slope of delta G, can be used to calculate the association rate constant against temperature.

Ab initio calculations were done to characterize the kinetics of F- + CH3Cl S(sub N)2 nucleophilic substitution. In particular, the rate constant versus relative translational energy E(sub rel) and CH3Cl temperature T were calculated. The results were found to be suggestive that during the entrance channel capture dynamics, the F- + CH3Cl relative translation and CH3Cl rotation motions are strongly and weakly coupled at low and high E(sub rel), respectively.

The rate constants and products for the reactions of Cl-(D2O)n + CH3Br (n=1-3) were determined. The n=1 reaction was examined from 238 to 478 K. The reaction mechanism was found to be ligand switching to form cl-(CH3Br) followed by thermal decomposition of the complex. Cl-(CH3Br) decompositions produces greater than 90% Br- + CH3Cl with the remainder being Cl- + CH3Br. The n=2 and 3 reactions also proceeded by ligand switching followed by thermal decomposition. The n=2 reaction was examined from 203 to 298 K. The main product was Cl-(D2O) with a smaller amount of Cl-(D2O)(CH3Br).

Behavior dynamics of the Cl- - - -CH3Br complex were examined through direct dynamic simulations. AM1-SRP1 and AM1-SRP2 were taken as different potential energy surfaces and compared to previous simulations of the PES1(Br) analytic potential energy function. The three surfaces exhibited quantitative differences in stationary point properties, including geometries and frequencies.

Classical trajectory studies of the intramolecular and unimolecular dynamics of the Cl(-)---CH3Br complex reveal two different types in the dynamics of this complex. Excitation of low-frequency modes leads to Cl(-)+CH3Br, while excitation of intramolecular high-frequency CH3Br modes produce ClCH3---Br- complex. Central barrier region of the potential energy surface traps this complex and shows extensive barrier recrossing. A dynamical bottleneck for energy transfer exists between Cl(-)---CH3Br and ClCH3---Br- complexes.

Semiclassical methods in developing quantum effects in molecular dynamics are reviewed. Selective applications illustrate the potential and efficiency of these methods.

A detailed study has been conducted on the dynamics of the back ET process after photoexcitation. Particularly, the effects of intramolecular vibrational modes and solvent dynamics and the influence of important physical parameters such as the electronic coupling and the temperature have been investigated.

A trajectory study of the reaction F- + CH3Cl -> FCH3 + Cl- is performed using the PES(F, Cl) analytic potential energy function. Trajectories will be used to determine the reaction rate constant, orientational effects of the reaction probability, the F- --- CH3CL and FCH3 --- Cl- lifetimes. impact of mode specific excitation on the reaction rate and mechanism, product energy, angular momentum and scattering angle distributions. Results show good agreement with experimental results.