Three ab initio potential energy surfaces of 2B2, 2A1 and 2R states for the Na+12 collision system are calculated on the QCISD(T)/LANL2DZ level. Three reaction channels, neutral reaction, chemical ionization and collision ionization, have been obtained based on analyzing the minimum energy reaction paths. The valence potential energy surfaces 2A1 and the ionic state 2B2 are crossed approximately at Rc=0.508nm. Na+I2→Na++I2 is an electronic non-adiabatic process.

A new quantum scattering approach, linear combination of arrangement channels-scattering wavefunction(LCAC-SW) proposed by Deng and co-workers [Sci. China B 24 (1994) 463] is used to calculate the collinear state-to-state reaction probabilities for the F+H2(0)→HF(υ)+H system on the 6SEC potential energy surface(PES). The calculated results reflect the character of PES accurately (there is a 'shallow hollow' along the reaction coordinate on the 6SEC potential energy surface). They are compared with other theoretical research reported in the literature. It is shown that the LCAC-SW approach is one of the successful quantum scattering methods.

In this Letter the LCAC-SW method has been extended to study the reaction dynamics for ion-pair formation processes on an M+X2→M+ +X2-reaction system involving two potential energy surfaces, i.e., the covalence state (M+X2). and the ionic state (M+ +X2-), and their crossing effect. The working equations for calculating the state-to-state probability have been derived based on the above two-state model, and the collinear state-selected probabilities for M+I2→M+ +I2-(M=Na, K, Cs)ion-pair formation systems have been obtained.

For the Cs+I2 collision system, a systematic theoretical study is first reported using the ab initio method. Three of eight possible channels are considered. The nonadiabatic coupling between the covalent state and the ionic one is calculated from different angles, especially the T-shape collision. The complete ion-pair formation potential energy surfaces of the T-shape collision in two electronic states (ionic 2B2 state and covalent 2A1 state) and the reactive surface of the linear collision are constructed at the QCISD(T)/SDD level. The main features of potential energy surfaces, such as the minimum energy reaction path, the crossing radius (Rc), and energy minimum geometries, are analyzed. The cross section of this titled system is calculated based on the harpoon mechanism and compared with the available experimental data and those obtained for the M+I2 (M=Li, Na) systems.

A theoretical study for the water-assisted mechanism in one-carbon unit transfer reaction catalyzed by glycinamide ribonucleotide transformylase (GAR Tfase) is investigated in which the proton transfers in an indirect way and the energy barrier for each transition state has been lowered about 80-100 kJ/mol when compared with the corresponding one in a nowater-involved mechanism. There are two possible pathways in each mechanism: one is concerted and the other is stepwise. Our results have verified the presumption from experiments that one water molecule can assist to achieve the whole reaction. Because the addition of this water molecule in the transition states can relax the strong strain in the unstable system and greatly lowered the energy barrier. The water-assisted paths are preferable to the no-water-involved ones and the bulk solvent effect of water is also discussed.