Investigating the UV-induced isomerization of Norbornadiene to Quadricyclane using ultrafast X-ray scattering*

The UV-induced isomerization of norbornadiene (NB) to quadricyclane (QC) is investigated using femtosecond gas-phase X-ray (16 keV) scattering. The 200-nm UV excites NB to the 3p Rydberg state, from where it isomerizes to QD via a conical intersection within sub-100-fs. Our preliminary results indicate that subsequent to the isomerization, which can be resolved due to the short pulse durations of both UV and X-ray pulses, the molecule is likely to dissociate into smaller products. Time-resolved identification of the isomerization and dissociation products and involved transient intermediates will elucidate this photochemical reaction. These findings are supported by ab initio calculations.