Photodissociation of isomeric dichloroethylenes in the ultraviolet: Effect of the second chlorine atom substitution on the dynamics

Abstract

We report the $C1^\ast(^2P_{1/2})$ production dynamics in the near-UV dissociation of three isomers (cis-, gem-, and trans-) of dichloroethylene using the conventional resonance enhanced multiphoton ionization technique. Substantial amounts of $C1^\ast$ are produced in the wavelength range 222–304 nm. The $C1^\ast$ quantum yield $(\phi^\ast)$ is maximum at 304 nm for all the isomers and $\phi^\ast_{cis}$ is markedly higher than $\phi^\ast_{gem}$ and $\phi^\ast_{trans}$ except at 222 nm. Existence of both direct and indirect dissociation pathways at these wavelengths complicates the $C1^\ast$ production dynamics. The higher value of $\phi^\ast_{cis}$ originates from a large contribution from direct dissociation via the $(n,\sigma^\ast)$ state.