Pump-Probe Photoionization Spectroscopy of penta methyl cyclopentadiene

The ultrafast curve crossing from the excited electronic state to the ground state in cyclic dienes often proceeds via conical intersections.~ Time-resolved experiments were performed by exciting the first excited state of pentamethylcyclopentadiene, as well as other methylated cyclopentadiene derivatives, with femtosecond pulses at 260 nm.~ Photoionization with a time-delayed probe pulse yields delay-time dependent mass and photoelectron spectra that reveal the ultrafast character of the curve crossing dynamics.~