Collision dynamics of Cs + ICH3→ Csl + CH3: backward vs. sideways scattering as a function of collision energy

Abstract

Differential reaction cross-sections for the Cs + ICH₃→ CsI + CH₃ system have been measured as a function of the collision energy using a simple molecular-beam apparatus. A new oven design suitable for producting stable beams of highly reactive metals was used to produce a Cs beam via the (oven) chemical reaction Ba(s)+ CsCl(s)→ BaCl(s)+ Cs(v). The Csl was detected over the whole angular laboratory range as a function of collision energy, E_T, from 0.15 to 0.56 eV. The analysis of the centre-of-mass angular and recoil velocity distributions of the product indicated (a) a backward peak corresponding to a direct, rebound mechanism, (b) increasing forward scattering as the collision energy increases, and (c) that the average translational energy of the products, E′_T, increases approximately linearly with increasing collision energy, E_T, as follows: E′_T/kJ mol^–1= 0.62E_T/kJ mol^–1+ 64.6. The backward to near-sideways scattering evolution with increasing E_T is discussed in the light of a possible insertion mechanism in addition to the (low collision energy) abstraction mechanism.