Quantum study of the Li+HF→LiF+H reaction

Abstract

Exact quantum stereodynamics: The steric effect for the Li+HF→LiF+H reactionIn this work we present a new global fit for the potential energy surface of the LiFH system. This fit is an improvement of a recently published one ͓Aguado et al., J. Chem. Phys. 106, 1013 ͑1997͔͒ for which more ab initio points have been calculated ͑from 644 to 2323͒. The reaction dynamics is studied using a time dependent treatment in reactant Jacobi coordinates in a body-fixed frame in which the internal coordinates are represented on a grid while Eulerian angles are described in a basis set. The centrifugal sudden approach is tested for total angular momentum Jϭ5 and used to calculate the reaction cross section. The reaction cross section shows oscillations as a function of kinetic energy. This is a consequence of strong interference effects between reactant and product channels and is in agreement with the recent experimental data.

Quantum stereodynamics of the Li+HF(v,j) reactive collision for different initial states of the reagent

“…In the present work the reaction dynamics is studied using a wave packet treatment described previously in detail, 19 and only a brief description is included here. Reactant Jacobi coordinates are used in which r is the HF internuclear vector, R is the vector joining the center of mass of HF to the Li atom, and ␥ is the angle between them.…”

“…16,19 In addition, there are molecular beam experiments for HF(vϭ0) 45 as well as experiments on the influence of the initial alignment of HF(vϭ1,jϭ1) on the reaction. 46,30 In this work we study the effect of the initial state excitation of the reactants on the LiϩHF(v, j) reactive collision, placing special emphasis on the correlation between the relative velocity of reactants and the rotational polarization of HF.…”

“…It is particularly interesting the determination of the role of the transition state on the reaction dynamics, mainly for energies close to the threshold, and the M ϩHX systems present a wide variety of situations, the reactions being endothermic, exothermic or thermoneutral depending on the nature of the metal atom ͑M͒ and of the hydrogen halide molecule ͑HX͒, and on the initial excitation of the reactants. Nowadays, there is an increasing number of theoretical works on these systems [15][16][17][18][19][20] due to the development of the methodology to describe the reaction dynamics of three atoms systems and to the appearance of accurate global potential energy surfaces ͑GPES͒ for some of these systems like LiϩHF 16,19 or NaϩHF. [20][21][22] Another source of valuable information is the reaction dynamics dependence on the relative velocity vectors between reactants and products and on the angular momenta involved in the process.…”

“…1. The reaction dynamics is studied with a time-dependent treatment within a body-fixed frame 19 using the centrifugal sudden approximation, which is described in Sec. II.…”

“…46,30 In this work we study the effect of the initial state excitation of the reactants on the LiϩHF(v, j) reactive collision, placing special emphasis on the correlation between the relative velocity of reactants and the rotational polarization of HF. We use a global PES recently published by us 19 whose main features are shown in Fig. 1.…”