Photodissociation dynamics of vibrationally excited CH2Cl2 molecules

Photodissociation of dichloromethane excited to the second C–H stretch overtone was performed by ∼235 nm photons that also tagged the Cl 2P3/2 [Cl] and spin–orbit excited Cl 2P1/2 [Cl*] photofragments via resonantly enhanced multiphoton ionization. The measured time-of-flight profiles together with the determined Cl*/Cl branching ratio suggest fast dissociation and involvement of several upper states of different symmetries mixing via curve crossing to release both Cl and Cl*. The determined ratio is higher than that obtained previously in the direct, almost isoenergetic, photodissociation of CH2Cl2 implying higher non-adiabaticity for vibrationally excited than for vibrationless ground state molecules.