Collision energy and product polarization effects in the Ca*(1D2)+ HCl → CaCl*(A, B)+ H reaction

Abstract

The collision energy dependence of the Ca(¹D₂)+ HCl → CaCl(A)+ H reaction cross-section has been measured over the low-energy range using the time-of-flight technique under crossed-beam conditions. The excitation function shows a step-like functionality which seems to be of a non-classical nature. These steps could be associated with the opening of internal transition states that become available as the total energy increases.

In addition beam–gas experiments have been carried out to measure the polarization of the CaCl*(B) emission to the ground electronic state. The collision-energy effects and the deviation from the kinematic limit of the product polarization have been also measured and they show a strong product rotational momentum alignment. The reaction stereodynamics are discussed with the aid of a dynamical model for kinematically constrained reactions. Finally a comparison of the present (full-collision) cross-beam reaction with the van der Waals (half-collision) photoinitiated reaction is also made.