Imaging the isotope effects in the ground state reaction of Cl CH4 and CD4

The ground state reactions of Cl + CH4 and CD4 were studied in a crossed-beam experiment, in which the ground state methyl products were probed using a time-sliced velocity imaging technique. By taking the images over the energy range of chemical significance - from reaction threshold to about 10 kcal/mol, the reactive excitation functions as well as the dependences of product angular distributions and of the energy disposals on initial collision energies were obtained. Comparing the dynamical attributes of the two isotopic reactions revealed an interesting isotope effect in product angular distributions. The previous reduced-dimensional quantum scattering calculations of Yu and Nyman appear to reproduce this isotope effect rather well. Yet, a physical understanding of its origin awaits further theoretical investigations.