Ultraviolet photodissociation of HCl in selected rovibrational states: experiment and theory

Abstract

Experimental and theoretical methods have been applied to investigate the effect of internal parent excitation on the iltraviolet photodissociation dynamics of HCl(X¹S ⁺) molecules. Jet-cooled H³⁵Cl molecules within a time-of-flight mass spectrometer were prepared by infra-red absorption in the following quanum states: v = 1, J = 0 and J = 5; v = 2, J = 0 and J = 11; v = 3, J = 0 and J = 7. The excited molecules were then photodissociated at l ~ 235nm and the Cl(²P_J) photofragments detected using (2+1) resonance enhanced multiphoton ionization. The results are presented as the fraction of total chlorine yield formed in the spin-orbit excited state, Cl(²P_1/2). The experimental measurements are compared with the theoretical predictions from a time-dependent, quantum dynamical treatment of the photodissociation dynamics of HCl(v=1-3,J=0). These calculations involved wavepacket propagation using the ab initio potential energy curves and coupling elements previously reported by M.H. Alexander, B. Pouilly, and T.Duhoo [J. Chem. Phys. 99 1752 (1993)]. The experimental results and theoretical predictions share a common qualitative trend, although quantitative agreement occurs only for HCl(v = 2).

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