Time-Resolved Study of Vacuum Ultraviolet Excited State Dynamics in Pyrrole Using 160 nm Femtosecond Laser Pulses Generated by Four-Wave Mixing in Argon

We have successfully utilized noncollinear four-wave mixing in argon to generate ~160 nm femtosecond laser pulses which can serve as the vacuum ultraviolet pump laser for time-resolved measurements. By performing a femtosecond time-resolved photoelectron imaging experiment, the ultrafast decay dynamics of pyrrole following single-photon excitation at ~160 nm is investigated. Two time constants of 50±15 and 250±50 fs are derived based on the analysis of the time-resolved photoelectron spectroscopy spectrum and assigned to the excited-state lifetimes of high-lying valence and Rydberg states. In particular, the analysis of the photoelectron angular distributions clearly indicates that the initially prepared valence * state(s) should be of somewhat Rydberg character.