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The quasi-classical trajectory method is used to study the effect of vibrational energy excitation of methane in the collision-induced dissociation (CID) by argon at hypothermal energies. The results have indicated that the energy transfer in Ar + C[H.sub.4] is enhanced by exciting the stretch vibrational modes of the colliding molecule and there is a strong impact of vibrational excitation on the CID of methane-like molecules at low-earth orbit (LEO) hyperthermal conditions.

The interpolation method of Collins and co-workers was used to construct an ab initio interpolated potential energy surface (PES) for the F + CH4 reactive system. The PES was used to carry out a detailed quasiclassical trajectory study of integral and differential cross sections, product rovibrational populations and internal energy distributions for the F + CH4 and F + CD4 reactions.

Large-scale classical trajectory calculations is performed to study the reaction Ar + CH4 -> CH3 + H + Ar in the temperature range 2500 (less than or equal to) T/K (less than or equal to) 4500. The energy-transfer parameters is obtained from trajectory calculations and compared with available values estimated from experiment using the master equation formalism.

A study of accurate single-valued double many-body expansion (DMBE) potential energy surface for the ground electronic state of HSO based on novel MR CISD ab initio energies suitably corrected for the complete one-electron basis-set/complete CI limit is presented. A n-body distributed polynomial approach, which implies using individual multinomial developments at the various stationary points is suggested.

The photodissociation of formic acid at 248 and 193 nm was investigated by classical trajectory and RRKM calculations using an interpolated potential energy surface, iteratively constructed using the B3LYP/aug-cc-pVDZ level of calculation. It was also found that the calculated CO vibrational distributions after disscociation of the parent molecule at 248 nm are in agreement with the experimental data.

The dynamics of the S + c-C3H reaction are theoretically studied. The collision process and the evolution of the reaction are the two steps that are found in the reactive collisions and the results suggest that the overall reaction rate is high and the production of SC3 + H may have a branching ratio of about 50%, SC + C2H being the other main product.