Primary and secondary dissociation pathways in the ultraviolet photolysis of Cl_2O
The photodissociation of dichlorine monoxide (Cl_2O) at 308, 248, and 193 nm was studied by photofragment translational energy spectroscopy. The primary channel upon excitation at 308 and 248 nm was Cl–O bond fission with production of ClO+Cl. A fraction of the ClO photoproducts also underwent spontaneous secondary dissociation at 248 nm. The center-of-mass translational energy distribution for the ClO+Cl channel at 248 nm appeared to be bimodal with a high energy component that was similar in shape to the 308 nm distribution and a second, low energy component with a maximum close to the threshold for the 2Cl+O(3P) channel. Observation of a bimodal distribution suggests that two pathways with different dissociation dynamics lead to ClO+Cl products. The high product internal energy of the second component raises the possibility that ClO is formed in a previously unobserved spin-excited state a 4∑−. Following excitation at 193 nm, a concerted dissociation pathway leading to Cl_2+O was observed in addition to primary Cl–O bond breakage. In both processes, most of the diatomic photofragments were formed with sufficient internal energy that they spontaneously dissociated. The time-of-flight distributions of the Cl_2+O products suggest that these fragments are formed in two different channels Cl_2(3II)+O(3P) and Cl_2(X1∑)+O(1D).
© 1994 American Institute of Physics. Received 9 December 1993; accepted 24 February 1994. This work was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA), and was supported by the Caltech President's Fund, NASA contract NAS 7-918, National Science Foundation PYI Award CHE-8957243, and a Dreyfus Newly Appointed Faculty Award. C.M.N. acknowledges support of a NASA Graduate Research Fellowship. We thank Timothy Lee and Steven Langhoff for providing unpublished results. Arthur Amos Noyes Laboratory of Chemical Physics, Contribution No. 8901.
Published - NELjcp94.pdf