Alteration of Cl spin–orbit branching ratios via photodissociation of pre-excited fundamental CH 3 stretch of CH 3CFCl 2

Abstract

The fundamental symmetric CH 3 stretch ( ν 2) in the ground electronic state of CH 3CFCl 2 is efficiently prepared by stimulated Raman excitation. The excited molecules are photodissociated by ∼235 nm photons that further tag Cl( 2 P 3/2 ) and Cl( 2 P 1/2 ) [Cl *] photofragments via (2+1) resonantly enhanced multiphoton ionization. The yield of both photofragments increases as a result of pre-excitation, indicative of energy flow from the excited C–H to the C–Cl bond and hence a better Franck–Condon overlap between the components of the wavefunction along the C–Cl coordinate. The Cl */Cl branching ratio is 0.60±0.09 in ∼235 nm photolysis of vibrationally excited molecules and 0.40±0.07 in that of vibrationless ground state CH 3CFCl 2.