Speed-Dependent Alignment and Angular Distributions of O(1D2)from the Ultraviolet Photodissociation of N2O

Photofragment ion imaging has been used to study the O(¹D₂) atoms produced in the ultraviolet ( 200 nm) photodissociation of nitrous oxide (N₂O) in a molecular beam. The images of O(¹D₂) reveal a speed-dependent angular distribution resulting from both variation in the spatial anisotropy of the recoil and alignment of the electronic angular momentum of the O(¹D₂) fragment. The orbital alignment effects are revealed by a change in the images when different transitions of the O atom are employed in the resonance enhanced multiphoton ionization (REMPI) process. By correlating the O atom anisotropies with previously measured values for the complementary N₂ fragments and comparing images collected on two different REMPI transitions, we calculate the relative branching ratios and anisotropies for the three different |m| values (defined along the product recoil axis) of the electronic angular momentum of the O(¹D₂) fragment. While m = 0 fragments have the highest probability for most O atom speeds, there is a significant change in the alignment and angular distributions for the slower O atoms. We use a simplified dynamical model supported by previous theoretical structure calculations to explain the measured trends and to estimate the relative branching in the excitation to two N₂O electronic states.

Speed-Dependent Alignment and Angular Distributions of O(1D2)from the Ultraviolet Photodissociation of N2O. David W. Neyer,Albert J. R. Heck,† and, David W. Chandler*, Janne M. Teule‡ and, and Maurice H. M. Janssen. The Journal of Physical Chemistry A 1999 103 (49), 10388-10397