Photodissociation dynamics of OClO at 157 nm

Abstract

Photodissociation of OClO at 157.6 nm excitation has been investigated using the photofragment translational spectroscopic technique. Two distinctive chemical dissociation channels have been observed; one is the binary dissociation process, OClO+hν→ClO+O; the other one is the triple dissociation process, OClO+hν→Cl+O+O. The branching ratio of the binary dissociation channel to the triple dissociation channel is determined to be 0.59:0.41. Bimodal vibrational distribution of the ClO product has been observed for the OClO→ClO(X 2Π)+O(3P,1D) channel, implying that two distinctive dissociation routes possibly exist in the binary dissociation process. The bimodal distribution is likely caused by the two dissociation pathways from two excited electronic states: the D(2A1) and E(2B1) states of OClO. These arguments are further supported by the results of the anisotropy parameter measurements for the binary dissociation channels. Experimental results also show that the OClO+hν→ClO(X 2Π)+O(1S) and OClO+hν→ClO(A 2Π)+O(3P) channels might also exist in addition to the ClO(X 2Π)+O(3P,1D) channel. In the triple dissociation process, experimental results show that the main product channel is the OClO+hν→Cl(2P)+O(1D)+O(3P) channel, while the OClO+hν→Cl(2P)+O(3P)+O(3P) channel is the minor one. The branching ratio of these two channels is determined to be 0.89:0.11. From the modeling of the time of flight spectra of the O atom product, it is believed that the triple dissociation process of OClO is a simultaneous process within the time scale of one rotation period. Two-photon dissociative ionization process OClO+hν→Cl++O2+e− has also been observed.