Photodissociation of vibrationally excited CH3Cl: modification of the dissociation dynamics

Vibrationally excited CH3Cl is prepared by laser excitation in the fourth CH stretch overtone transition and photodissociated at fixed wavelengths near 238 nm which also probe the Cl(2P32) and Cl(2P12) photofragments through (2 + 1) resonance enhanced multiphoton ionization in a time-of-flight mass spectrometer. Jet cooling reveals two partially resolved bands, which are assigned as transitions to the local-mode [5,0,0]A1,E and [3,0,0] + 4ν2 (A1,E) levels. The ratio of Cl(2P12) to Cl(2P32) spin-orbit populations was found to be 1.08 ± 0.08 for 238 nm photolysis of vibrationally excited CH3Cl, significantly larger than the spin-orbit population ratio (0.27 ± 0.01) in Cl fragments from the 235 nm photolysis of ground state CH3Cl.