Photoelectron elliptical dichroism spectroscopy of resonance-enhanced multiphoton ionization the 3s, 3p and 3d Rydberg series in fenchone

The resonance-enhanced multiphoton ionization of chiral molecules by elliptically polarized laser pulses produces photoelectron angular distributions that are forward/backward asymmetric with respect to the light propagation axis. We investigate this photoelectron elliptical dichroism in the (2 + 1)-photon ionization of fenchone molecules, using wavelength tunable femtosecond UV pulses. We show that the photoelectron elliptical asymmetry is extremely sensitive to the intermediate resonant states involved in the ionization process, and enables electronic couplings to be revealed that do not show up so clearly when using circularly polarized light. In 2 + 1 fs-REMPI of chiral molecules, recording the forward-backward asymmetry in the photoelectron distribution as a function of the ionizing light ellipticity reveals the non-adiabatic couplings occurring during the 70 fs duration of the pulses.