VUV-induced Dynamics of the Electronically Excited C2D4 Molecule in a Single-Color Pump-Probe Experiment

The ultrafast non-adiabatic dynamics of the electronically excited ethylene molecule C2H4 and its deuterated isotopologue C2D4 are studied with time-resolved photoelectron spectroscopy after π→π∗ excitation via irradiation with light in the vacuum ultraviolet spectral range. Sub-20-fs pulses, generated as the fifth harmonic of a Ti:Sa laser system, are split and delayed in an all-reflective Michelson-type interferometer, enabling a single-color pump-probe experiment. In addition to the ultrafast non-adiabatic relaxation process of C2H4, we find more complex dynamics exhibited by the delay-dependent photoelectron yield of C2D4, identified as a signature of the delayed dissociative ionization of the parent ion.