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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.

Low-energy collision-induced dissociation (CID) of deprotonated l-cysteine S-sulfate, [cysS-SO 3 ] - , delivered in the gas phase by electrospray ionization, has been found to provide a means to form deprotonated l-cysteine sulfenic acid, which is a fleeting intermediate in biological media. The reaction mechanism underlying this process is the focus of the present contribution. At the same time, other novel species are formed, which were not observed in previous experiments. To understand fragmentation pathways of [cysS-SO 3 ] - , reactive chemical dynamics simulations coupled with a novel algorithm for automatic determination of intermediates and transition states were performed. This approach has allowed the identification of the mechanisms involved and explained the experimental fragmentation pathways. Chemical dynamics simulations have shown that a roaming-like mechanism can be at the origin of l-cysteine sulfenic acid.

The tsscds method, recently developed in our group, discovers chemical reaction mechanisms with minimal human intervention. It employs accelerated molecular dynamics, spectral graph theory, statistical rate theory and stochastic simulations to uncover chemical reaction paths and to solve the kinetics at the experimental conditions. In the present review, its application to solve mechanistic/kinetics problems in different research areas will be presented. Examples will be given of reactions involved in photodissociation dynamics, mass spectrometry, combustion chemistry and organometallic catalysis. Some planned improvements will also be described.

In this paper, we briefly review the boxed molecular dynamics (BXD) method which allows analysis of thermodynamics and kinetics in complicated molecular systems. BXD is a multiscale technique, in which thermodynamics and long-time dynamics are recovered from a set of short-time simulations. In this paper, we review previous applications of BXD to peptide cyclization, solution phase organic reaction dynamics and desorption of ions from self-assembled monolayers (SAMs). We also report preliminary results of simulations of diamond etching mechanisms and protein unfolding in atomic force microscopy experiments. The latter demonstrate a correlation between the protein's structural motifs and its potential of mean force. Simulations of these processes by standard molecular dynamics (MD) is typically not possible, because the experimental time scales are very long. However, BXD yields well-converged and physically meaningful results. Compared with other methods of accelerated MD, our BXD approach is very simple; it is easy to implement, and it provides an integrated approach for simultaneously obtaining both thermodynamics and kinetics. It also provides a strategy for obtaining statistically meaningful dynamical results in regions of configuration space that standard MD approaches would visit only very rarely.