VUV photodissociation dynamics of OClO: binary and triple dissociation

Abstract

Photodissociation of OClO at 157.6 nm excitation has been investigated using the photofragment transnational spectroscopic technique. Two distinctive chemical dissociation channels have been observed: one is the binary dissociation process, OClO + hv yields ClO + O; the other one is the triple dissociation process, OClO + hv yields 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 yields ClO (X<SUP>2</SUP> (Pi) ) + O(<SUP>3</SUP>P, <SUP>1</SUP>D) 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(<SUP>2</SUP>A<SUB>1</SUB>) and E(<SUP>2</SUP>B<SUB>1</SUB>) 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 + hv yields ClO(X<SUP>2</SUP> (Pi) ) + O(<SUP>1</SUP>S) and OClO + hv yields ClO(A <SUP>2</SUP>(Pi) ) + O(<SUP>3</SUP>P) channels might also exist in addition to the ClO(X<SUP>2</SUP>(Pi) ) + O(<SUP>3</SUP>P, <SUP>1</SUP>D) channel. In the triple dissociation process, experimental results show that the main product channel is the OClO + hv yields Cl(<SUP>2</SUP>P) + O(<SUP>1</SUP>D) + O(<SUP>3</SUP>P) channel, while the OClO + hv yields Cl(<SUP>2</SUP>P) + O(<SUP>3</SUP>P) + O(<SUP>3</SUP>P) 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.