Ultrafast Deep and Vacuum Ultraviolet Gas-Filled Hollow-Core Fibre Sources for Time-Resolved Photoelectron Spectroscopy

Summary form only given. Soliton-driven resonant dispersive-wave (RDW) emission is an established route to the generation of frequency tunable ultrafast pulses. In gas-filled anti-resonant guiding hollow-core photonic-crystal fibre (HC-PCF), continuous tuning of RDW generation in both the vacuum (VUV) and deep ultraviolet (DUV) to visible (110 nm to 550 nm) has been achieved [1] and fully characterised to have a temporal duration of a few fs in DUV [2]. Due to the high conversion efficiency (up to 10%), relatively low pump energies are required (few μJ) to get useful UV energy, and so high repetition-rate pump sources can be used [3]. Furthermore, the generated UV emission reproduces the polarization state of the pump pulse. Combined, all of these features make RDW-emission in gasfilled HC-PCF an ideal, and rather unique, source for ultrafast pump-probe spectroscopy in the ultraviolet region. Here we show, for the first time, the use of RDW-emission for time-resolved molecular spectroscopy (see Fig. 1) in the DUV [5]. The time-resolved photoelectron velocity -map imaging technique we use reveals complex non adiabatic dynamical processes operating at timescales of few tens of fs in the styrene molecule following excitation by RDW-emission over the 242-258 nm region, in conjunction with a third harmonic probe derived from out 800 nm pump laser. The high temporal resolution already achieved allows us to follow the non-adiabatic molecular dynamics [5]. By using RDW-emission as both the pump and probe in the DUV and VUV, we expect to soon improve the temporal resolution to a few fs.