Channel-resolved ultrafast dissociation dynamics of NO2 molecules studied via femtosecond time-resolved ion imaging

Abstract

The ultrafast dissociation dynamics of NO $_2$ molecules was investigated by femtosecond laser pump-probe mass spectra and ion images. The results show that the kinetic energy release of NO $^+$ ions has two components, 0.05 eV and 0.25 eV, and the possible dissociation channels have been assigned. The channel resolved transient measurement of NO $^+$ provides a method to disentangle the contribution of ultrafast dissociation pathways, and the transient curves of NO $^+$ ions at different kinetic energy release are fitted by a biexponential function. The fast component with a decay time of 0.25 ps is generated from the evolution of Rydberg states. The slow component is generated from two competitive channels, one of the channel is absorbing one 400 nm photon to the excited state $A^2$ B $_2$ , which has a decay time of 30.0 ps, and the other slow channel is absorbing three 400 nm photons to valence type Rydberg states which have a decay time less than 7.2 ps. The channel and time resolved experiment present the potential of sorting out the complex ultrafast dissociation dynamics of molecules.