Femtosecond Time-Resolved Photoelectron Angular Distributions Probed during Photodissociation ofNO2

Femtosecond time-resolved photoelectron angular distributions (PADs) are measured for the first time in the molecular frame of a dissociating molecule. Various stages of the dissociation process, ${\mathrm{NO}}_2\to \mathrm{NO}\left(C{}_{}{}^2{}_{}{}^{}\Pi \right)+\mathrm{O}\left({}_{}{}^3{}_{}{}^{}P\right)$, are probed using ionization of the $\mathrm{NO}\left(C{}_{}{}^2{}_{}{}^{}\Pi \right)$ fragment to ${\mathrm{NO}}^{+}\left(X{}_{}{}^1{}_{}{}^{}\Sigma _{}^{+}{}_{}{}^{}\right)$. The PADs evolve from forward-backward asymmetric with respect to the dissociation axis at short time delays ( $\le 500$ fs) to symmetric at long time delays ( $\ge 1$ ps). Changes in the PADs directly reflect the time-dependent separation and reorientation of the dissociating photofragments.