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
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