Transition probabilities found for M + CH4 reactions (M = zinc, copper)

Abstract

AbstractTransition probabilities between the lowest energy levels of M + CH4 (M = Zn, Cu) reactions were obtained through nonadiabatic crossings using a modification of the Landau–Zener (L–Z) theory. Hartree Fock self consistent field (HF‐SCF) ab initio calculations were utilized to obtain the reaction pathways by means of the PSHF program, while pseudopotentials for representing the core–core and core‐valence interaction were applied. The correlation energy is taken into account by means of multireference variational and perturbative configuration interaction calculations to second order using CIPSI code. The variational space generated in iterative manner includes more than 250 determinants, while the perturbative space is about 3 × 107 configurations. The perturbative contribution is about 40% of the total correlation energy recovered. The time dependent L–Z theory was developed through the reaction coordinate r (distance). An extension of the latter theory to the reaction coordinate θ (angle) was used in this case. Then, the nonadiabatic crossings depend on both the angular velocity and the moment of inertia, among other things. The transition probability of the system HMCH3 (M = Zn, Cu) leading from one energy level to another is calculated through an avoided crossing. This method has been previously tested on gallium‐methane and gallium‐silane reactions for which the theoretical probability transitions between potential energy surfaces of gallium‐methane reactions agree with experimental quenching branching fractions with great accuracy. © 2008 Wiley Periodicals, Inc., 2008