Cl∗(²P_½) production dynamics from chloroiodomethane (CH₂ICl) in the ultraviolet

Abstract

Dynamics of Cl∗(²P_½) production from chloroiodomethane dissociation has been investigated in the near ultraviolet (222≤λ_ex≤304 nm). The quantum yield of Cl∗((²P_½) production, φ∗(Cl), has been measured by monitoring nascent Cl(²P_3/2) and Cl∗ concentrations and compared with the quantum yield of I∗(²P_½) production at the same excitation wavelengths. In the near ultraviolet where most of the transition strength is carried by the σ∗(C-I)← n(I) transition, the measured Cl½ quantum yield decreases as a function of increasing photolysis wavelength. An interchromophore energy transfer mechanism between the C-I and C-Cl chromophores has been proposed to rationalize Cl∗ production since the direct excitation of the σ∗(C-I)← n(Cl) transition is less likely at wavelengths ~100 nm away from the peak of the C-Cl absorption band.