A theoretical study on an isotope effect in the CH3+H2 → CH4+H reaction

Vibrationally adiabatic ground-state potential curves for the CH3+H2 → CH4+H (I) and CD3+H2 → CD3H+H (II) reactions were obtained by adding zero-point energies of harmonic vibrations orthogonal to intrinsic reaction coordinate (IRC) to the bare potential curves along IRC. It was clarified that both the barrier height and barrier width of reaction II are smaller than those of reaction I. This computational result qualitatively explains the experimental observation of T. Momose, H. Hoshina, N. Sogoshi, H. Katsuki, T. Wakabayashi, T. Shida [J. Chem. Phys. 108 (1998) 7334] that reaction II occurs but reaction I does not occur in solid parahydrogen at 5 K.