Cl∗(2P1/2) production dynamics from chloroiodomethane (CH2ICl) in the ultraviolet

Dynamics of Cl∗(2P1/2) production from chloroiodomethane dissociation has been investigated in the near ultraviolet (222 ⩽ λex ⩽ 304 nm). The quantum yield of Cl∗(2P1/2) production, ϕ∗(Cl), has been measured by monitoring nascent Cl(2P3/2) and Cl∗ concentrations and compared with the quantum yield of I∗(2P1/2) 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 Cl∗ 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–Cl) ← n(Cl) transition is less likely at wavelengths ∼100 nm away from the peak of the C–Cl absorption band.