Dissociative multiphoton ionization of NO[sub 2] studied by time-resolved imaging

André T. J. B. Eppink, Benjamin J. Whitaker, Eric Gloaguen, Benoit Soep, A. Marcela Coroiu, David H. Parker
2004 Journal of Chemical Physics  
We have studied dissociative multiphoton ionization of NO 2 by time-resolved velocity map imaging in a two-color pump-probe experiment using the 400 and 266 nm harmonics of a regeneratively amplified titanium-sapphire laser. We observe that most of the ion signal appears as NO ϩ with ϳ0.28 eV peak kinetic energy. Approximately 600 fs period oscillations indicative of wave packet motion are also observed in the NO ϩ decay. We attribute the signal to two competitive mechanisms. The first
more » ... three-photon 400 nm absorption followed by dissociative ionization of the pumped state by a subsequent 266 nm photon. The second involving one-photon 400 nm absorption to the 2 B 2 state of NO 2 followed by two-photon dissociative ionization at 266 nm. This interpretation is derived from the observation that the total NO ϩ ion signal exhibits biexponential decay, 0.72 exp(Ϫt/90Ϯ10)ϩ0.28 exp(Ϫt/4000Ϯ400), where t is the 266 nm delay in femtoseconds. The fast decay of the majority of the NO ϩ signal suggests a direct dissociation via the bending mode of the pumped state.
doi:10.1063/1.1795654 pmid:15485239 fatcat:dsj3vmfq2rd6pfeeg3l6vndjly