Semiclassical calculations on the energy dependence of the steric effect for the reaction Ca(1D)+CH3F(jkm=111)→CaF+CH3

Abstract

In a previous article [A. J. H. M. Meijer, G. C. Groenenboom, and A. van der Avoird, J. Chem. Phys. 101, 7603 (1994)] we investigated the energy dependence of the steric effect of the reaction Ca ( *D)+CH3F (jkm = 111) ->CaF (A 2ri)+ C H 3 using a quasiclassical trajectory method. It was found that we could not reproduce the experimental results for this reaction [M. H. M. Janssen, D. H. Parker, and S. Stolte, J. Phys. Chem. 95, 8142 (1991)]. In this article, we reinvestigate this reaction using a semiclassical method, in which the rotation of the molecule and the electronic states of the interacting atom and molecule are treated quantum mechanically. For the chemical reaction we use a model which correlates the projection of the electronic orbital angular momentum of the Ca atom on the intermolecular axis with the projection of the electronic orbital angular momentum of the CaF product on the diatomic axis [M. Menzinger, Polon. Phys. Acta A 73, 85 (1988)]. This model is applied to examine the CaF (A 2U , B 22 + , A' 2A) exit channels separately. We conclude that we can reproduce the experimental results for the steric effect using this model. The improvement with respect to the classical trajectory results is shown to be due primarily to the extended reaction model rather than to the semiclassical description of the dynamics. We find trapping and reorientation in the semiclassical calculations, as in the previous classical trajectory results, but also non-adiabatic effects are present. The latter do not affect the reactive cross sections very much.

Transition State Spectroscopy of the Photoinduced Ca + CH3F Reaction. 2. Experimental and Ab Initio Studies of the Free Ca···FCH3 Complex

“…Isaacson and Muckerman on Ca+HCl [37], an extensive exploration of the ground state PES is available for Be/HF [38] as well as information on excited PES and the corresponding excited state dynamics for Ca/HCl [39,40,41,42] and Ca, Ba/CH 3 F [40,24].…”

“…The work on Ca/CH 3 F [40] is a semiclassical treatment of the dynamics, based on multipolar expansion of the electrostatic interaction between Ca and CH 3 F. It is aimed at unraveling steric effects in the bimolecular collision between Ca(4s3d 1 D) and CH 3 F, spatially oriented.…”

Entrance Channel Effects in the Reaction of Aligned Ca(1P) with HCl

“…[33][34][35][36] Actually, since one expects no activation barrier for a reaction of this type, we use a version of the ADLC model with zero energy barrier, in which it is simply assumed that reaction occurs if the angle R at the moment of impact (R ) R h ) is smaller than a certain cutoff angle 0 . [26][27][28] This defines a cone of reaction,…”

“…Although this model is extremely simple, it was successful in rationalizing the observed energy dependence of the steric effect in the reactions of Ca( 1 D) with CH 3 X, 5,6,29 as a consequence of the same type of long-range effects considered here. [25][26][27][28] In order to obtain the reactive cross section for the two exit channels Λ f (A 2 Π and B 2 Σ + ), the trajectory calculations must be performed for a number of impact parameters b and for different initial rotational states (j i , m i ). For a Σ polarized Ca-( 1 P) substate we start with µ i ) 0 and for a Π polarized substate with µ i ) (1.…”

“…The semiclassical calculations were performed with the same program as in ref 27. For details regarding numerical integration over the angles, the propagation, etc., see ref 27. …”