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Dave Townsend

Publications and source records attributed to Dave Townsend.

2 recordsLinked to original sources

Direct Asymmetric Photochemistry with Synthetic Chiral Light

Circularly polarized light has long been used to distinguish the two mirror images of chiral molecules. Recently, a conceptual breakthrough has predicted that a new form of optical fields - synthetic chiral light - could usher in an 'electric-dipole revolution' in chiroptical interactions. We report the first experimental evidence for this prediction in the optical domain, using a three-dimensional laser electric field synthesized to trace a chiral pattern. The ionization and fragmentation of chiral molecules was found to depend on both the molecular handedness, and the handedness and geometry of the synthetic chiral field. Supported by two theoretical models, our results demonstrate that synthetic chiral light can induce strong chiroptical interactions, opening new horizons for asymmetric photochemistry and chiral analysis.

physics.chem-ph

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

physics.chem-ph