10min:

PRASHANT. CHANDRA. SINGH, L. SHEN, A. G. SUITS, Department of Chemistry, Wayne State University, Detroit, MI 48201; G. C. MCBANE, Grand Valley State University, Allendale, MI 49401; R. SCHINKE, Max Planck Institute for Dynamics and Self-organization, D-37073 Gottingen, Germany.

Ozone photodissociation below 234 nm gives rise to a bimodal recoil velocity dstribution in the minor channel giving O (³P_j) as a product, and the source of this bimodality has so far eluded definitive explanation. It has long been asribed to coincident production of highly vibraitonally excited O₂ possibly through some distinct intersection seam of the relevant potential energy surfaces, but extensive theoretical effort has failed to find a plausible pathway for this. We have used the DC sliced imaging method to reinvestigate the product O (³P_j) of ozone photodissociation at 226nm at very high velocity resolution. The experimental results are focused exclusively on the slow component for the O (³P_j) fragments formed in the photodissociation of ozone at the 226.06 nm for J=1 and 225.65 nm for J=2. The total translational energy distributios for the slow components show two distinct peaks that are coincident, within 0.01 eV, with the onset of v=0 and 1 of the A'³ _u state of O₂ as a cofragment. Furthermore, trajectory calculations show that, at this excitation energy, the region of the ozone “B” state that correlates with the Herzberg states of oxygen is accessible, and a fraction of trajectories reach this intersection region. These combined experimental and theoretical investigations provide compelling evidence that the origin of the slow peaks in the O(³P_j) product of ozone dissociation below 234 nm is the channel yielding the A'³ _u state of O₂ as a coproduct.