Probing the ultrafast ring-reconfiguration reaction from quadricyclane to norbornadiene *

We report the results of an experiment studying the UV-induced ring-reconfiguration reaction of a multicyclic hydrocarbon, quadricyclane, using time-resolved XUV photoelectron spectroscopy (TRPES). Utilizing a time-of-flight magnetic bottle spectrometer and 19-eV photons from the seeded free-electron laser FERMI, we probe the excitation to 3p and 3s Rydberg states induced by the absorption of a 200-nm photon, the subsequent ultrafast relaxation dynamics to the electronic ground state, and the isomerization dynamics to the bicyclic norbornadiene. The results are compared to a previous UV-TRPES study conducted at a slightly different excitation wavelength of 208 nm.