AB-INITIO STUDIES ON THE DYNAMICAL PROPERTIES OF THE REACTION NH(X-3-SIGMA(-))-]N(S-4)+H-2(H)

The geometries of the reactant, product, and transition state of the t itled reaction were optimized at the UHF, UMP2, and UMP4 levels with t he double- and triple-zeta basis sets as well as polarization function s using the energy gradient method. The potential barrier for this rea ction was calculated to be 1.68 kcal/mol at the MP-SAC4/6-311G* level . The intrinsic reaction coordinate (IRC) was traced at the UMP2/6-311 G* level, and the energy profile along the LRC was refined with the s ubsequent MP-SAC4/6-311G* calculations. The calculated rate constants at the MP-SAC4/6-311G* level are in good agreement with the experime ntal values in the temperature range 2000-3000 K.