Ultrafast Molecular Spectroscopy Using a Hollow-Core Photonic Crystal Fibre Light Source

We demonstrate, for the first time, the application of rare-gas filled hollow-core photonic crystal fibres (HC-PCFs) as tuneable ultraviolet light sources in femtosecond pump-probe spectroscopy. The time-resolved photoelectron imaging technique reveals non-adiabatic dynamical processes operating on three distinct timescales in the styrene molecule following excitation over the 242-258 nm region. These include ultrafast (<100 fs) internal conversion between the S2(pipi*) and S1(pipi*) electronic states and subsequent intramolecular vibrational energy redistribution within S1(pipi*). Compact, cost-effective and highly efficient bench-top HC-PCF sources have huge potential to open up many exciting new avenues for ultrafast spectroscopy in the ultraviolet and vacuum ultraviolet spectral regions. We anticipate that our initial validation of this approach will generate important impetus in this area