Oscillating reactivity of the light atom transfer reaction Cl + HCl → ClH + Cl: Dependence on the nature of the potential energy surface

The hydrogen atom transfer reaction Cl + HCl → ClH + Cl was used as a model for investigating the occurrence of oscillations in the reactivity as a function of collision energy for reactions in which a light atom L is transferred between two heavy atoms H and H′, H + LH′ → HL + H′. Very extensive three-dimensional quasi-classical trajectory calculations, under a variety of conditions and employing three LEPS potential energy surfaces, were carried out for this purpose. The three surfaces have very similar properties for the collinear Cl-H-Cl configuration but considerably different widths of the reactive cone of acceptance. Significant oscillations were obtained for two of the surfaces. The surface for which the strongest oscillations were observed is characterized by strong anisotropic attractive forces which lead to reorientation of the reagents to a nearly collinear configuration even when the initial orientation angle (the angle between the relative velocity vector and the axis of the HCl molecule) is large. The results of this study indicate that the most promising experiments for detecting oscillations should be scattering experiments with oriented molecular beams.