Reactions of N(22D) with CH3OH and Its Isotopomers

The reaction pathways of N( 2 D) with methanol and its isotopomers were specified by laser pump-and-probe experiments and molecular orbital calculations. It was shown experimentally that CH 3 OH deactivates N( 2 D) efficiently to produce ground-state NH and OH radicals. The nascent state distributions of these radicals are not statistical, suggesting that the intermediate species decompose before energy randomization. A similar result was obtained for ND and OD formed in the N( 2 D)/CD 3 OD system. NH, ND, OH, and OD radicals were identified in partially deuterated systems. The ND/NH population ratio measurements show that NH and ND radicals are produced from both hydroxyl and methyl positions, but the former plays more important roles, one order of magnitude, than the latter. This is consistent with the result of ab initio molecular orbital calculations that the most favorable initial step is the addition of N( 2 D) to the O atom. The OD/OH ratio in the CD 3 OH system as well as the OH/OD ratio in the CH 3 OD system is 0.5. OH(OD) is produced mainly by the C−O bond scission just after the insertion of N( 2 D) into a C−H(C−D) bond, but the bond scission after intramolecular H/D scrambling is also important. This is also consistent with the result of calculations that the barrier height for the H(D) atom migration is much lower than the available energy.