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(P-2(3/2)) and Cl(P-2(1/2)) 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] + 4 nu(2) (A(1),E) levels. The ratio of Cl(P-2(1/2)) to Cl(P-2(3/2)) 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. (C) 1997 Elsevier Science B.V.