DYNAMIC ISOTOPE EFFECT ON THE PRODUCT ENERGY PARTITIONING IN CH2OH-]CHO++H-2()

The deuterium isotope effect on the product energy partitioning in the title reaction was investigated both experimentally and theoretically . The measured kinetic energy release (KER) showed a significant depen dence on the position of deuteration. A reliable potential energy surf ace of the reaction was constructed from ab initio results using the r ecently developed interpolation algorithm. The classical trajectory ca lculation on this surface well reproduced the experimental finding. Cl ose inspection of the potential energy surface revealed that the isoto pe effect on KER and the product rotations arose from the alteration o f the symmetry of the reaction path near the transition state induced by the mass change upon isotopic substitution. The product vibrations were found to be affected by the change in the coupling constants whic h also arose from the mass-dependent change in the reaction path. Poss ibility of the quantum mechanical tunneling was also considered. Tunne ling-corrected classical trajectory results were in excellent agreemen t with the experimental ones, indicating that the reaction proceeds vi a barrier penetration below the threshold. (C) 1998 American Institute of Physics. [S0021-9606(98)03137-7].