THEORETICAL-STUDY OF H(D)- EFFECTS OF PRESSURE, TEMPERATURE, AND QUANTUM-MECHANICAL TUNNELING ON H(D)-ATOM DECAY AND OH(D)-RADICAL PRODUCTION(N2O )

RRKM; calculations based on the theoretical BAC-MP4 potential energy d ata and molecular parameters for H(D) + N2O reactions have been carrie d out by solving master equations which incorporate tunneling effect c orrections for the H-atom (or D-atom) addition and migration processes . The generalized reaction mechanism involves an energetic adduct (HNN Odagger or DNNOdagger), which can redissociate back to the reactants, undergo an H-atom (or D-atom) migration to form products, or it could be stabilized via collisional deactivation. The thermal rate coefficie nts for the unimolecular decomposition and bimolecular chemical activa tion according to this mechanism were obtained from the numerical solu tion of master equations based on the Nesbet algorithm, microscopic re versibility, and Gaussian elimination, with the weak collision assumpt ion using the exponential-down model. The convoluted effect of pressur e and tunneling accounts for the observed curvature in the Arrhenius p lots for the reactions of both H and D atoms. The calculated results a re in excellent agreement with the experimental data of Marshall et al . (J. Phys. Chem. 1989, 93, 1922).