Energetics and Spin- and Lambda-Doublet Selectivity in the Infrared Multiphoton Dissociation DN3 yields DN(X 3 Sigma(-), a 1 Delta) + N2(X 1 Sigma g (+)): Experiment

摘要

Multiphoton vibrational excitation of deuterated hydrazoic acid, DN3, by a CO2 laser (I=10 GW/sq.cm.) leads to dissociation forming DN in both X 3 Sigma(-) (spin forbidden) and a 1 Delta (spin allowed) electronic states. Under collisionless conditions, the nascent DN fragments were probed via laser induced fluorescence, to determine initial product state distributions. The DN(X 3 Sigma(-) molecules are formed predominantly in the symmetric F1 and F3 spin-rotation states with little population (< or = 6%) in the antisymmetric F2 levels. There is no significant population (< 3%) in excited DN 3-Sigma(-) vibrational levels. The distribution of rotational states is Boltzmann-like, characterized by a rotational temperature of about 920 K for the F1, F3 states and 500 K for F2 levels. Doppler profiles showed a large kinetic energy release of about 10 100 cm total in the triplet channel. The DN(1 Delta) products are formed preferentially in the symmetric Delta(A'), e-labeled lambda doublet levels: Delta(A')/Delta(A )=1.44. The DN(1 Delta) is formed with no vibrational excitation (<2%); the rotational states are populated Boltzmann-like with a rotational temperature of 425 K. Doppler profiles give a total kinetic energy of about 1500/cm in this channel. The observed DN(3 Sigma(-) spin- and DN(1 Delta) Lambda-doublet selectivities reflect the symmetry properties of a planar transition state and that the low degree of DN(3 Sigma(-) rotational and vibrational excitation is also expected from the transition state geometry. Reprints. (jhd)