Femtosecond time-resolved photoelectron–photoion coincidence imaging studies of dissociation dynamics

We present the first results using a new technique that combines femtosecond pump–probe methods with energy- and angle-resolved photoelectron–photoion coincidence imaging. The dominant dissociative multiphoton ionization (DMI) pathway for ${\mathrm{NO}}_{\mathrm{2}}$ at 375.3 nm is identified as three-photon excitation to a repulsive potential surface correlating to $\mathrm{NO}{\mathrm{(C\hspace{0.17em}}}^2\mathrm{\Pi )+}\mathrm{O}{(}^3\mathrm{P)}$ followed by one-photon ionization to ${\mathrm{NO}}^{\mathrm{+}}{\mathrm{(X\hspace{0.17em}}}^1{\Sigma }^{+}\mathrm{).}$ Dissociation along this surface is followed on a femtosecond timescale.