The 248 nm photodissociation of ClNO2 studied by photofragment translational energy spectroscopy

The photodissociation of nitryl chloride (ClNO2), a potentially active spec ies in atmospheric chemistry, has been studied following excitation into th e weakly structured band at 248 nm using photofragment translational energy spectroscopy. Among the energetically accessible decay channels, only the formation of the primary fragments Cl + NO2 has been found to be active inv olving the fission of the weakest bond (D-0(Cl-NO2) = 138 kJ/mol). The two fragments exhibit a well-structured translational energy distribution. The structure is attributed to different decay routes which include the formati on of NO2 fragments in different electronic states. Thus, about 30% are pro duced in the ground state while the rest, in accordance with the kinetic en ergy structure and the available fragment energy, is consistent with produc tion in the A(2)B(2) and (BB1)-B-2 excited electronic states. The similar r ovibrational energy channeled into NO2 along the three decay routes suggest s an indirect decay with an exit barrier. In addition, at high laser fluenc es secondary photodissociation of the hot or electronically excited NO2 pro ducts to NO + O was observed.