Collision energy effects in the Cs+ICH3→CsI+CH3 reaction

Abstract

Differential and total reaction cross sections for the Cs+ICH3→CsI+CH3 system have been measured as a function of the collision energy by using the crossed beam technique. The analysis of the center-of-mass angular and recoil velocity distribution of the products indicated: (a) a backward peak character corresponding to a direct rebound mechanism at low collision energy; (b) over the collision energy range from 0.15 up to 0.56 eV, the backward character shifts to near sideways scattering. A direct interaction with product repulsion (DIPR) model analysis of this collision energy evolution showed an increasing participation of bent transition state configurations, which might be in competition with the purely collinear one at lower collision energy; (c) that the average products’ translational energy Ē′T increases approximately linearly with increasing collision energy ĒT as follows: Ē′T/kJ mol−1 =0.62 ĒT/kJ mol−1+58.5. Complete laboratory differential reaction cross-section measurements were carried out at 21 different relative velocities, then integrated and normalized to yield the total flux and reaction cross section in relative units. Over the available range of ET, σR(ET) shows a minimum at ET≂0.23 eV. A comparison of the present excitation function shape with current theoretical treatments is also reported.