Photodissociation dynamics of dichlorocarbene at 248 nm

Abstract

The dynamics of the 248 nm photodissociation of the CCl₂ molecule have been investigated in a molecular beam experiment. The CCl₂ parent molecule was generated in a molecular beam by pyrolysis of CHCl₃, and both CCl₂ and the CCl photofragment were detected by laser fluorescence excitation. The 248 nm attenuation cross sections was estimated from the reduction of the CCl₂ signal as a function of the photolysis laser fluence. The internal state distribution of the CCl photofragment was derived from analysis of laser fluorescence excitation spectra in the A ²Δ − X ²Π band system. The CCl(X ²Π, v = 0) rotational state distribution was found to be bimodal, with maximum populations at N ≈ 10 and 85, and was dependent upon the source backing pressure, and hence upon the internal state distribution of the CCl₂ precursor. The 248 nm photodissociation dynamics appears to involve two separate channels, namely nearly impulsive rotational energy release and predissociation with little rotational energy imparted to the CCl fragment.