Ultraviolet (UV) radiation has a key role in a vast range of scientific areas, including light-harvesting technologies, atmospheric chemistry and biochemistry. In laboratories, the generation and utilization of few-femtosecond UV pulses, i.e., <5 fs, is extremely challenging, but promises to reproduce ultrafast molecular processes that occur in nature and to identify their underlying mechanisms. We will exploit the recent advances of ultraviolet light sources to develop a unique UV-pump UV-probe beamline for time-resolved spectroscopy through the generation of few-cycle UV pulses at a high repetition rate (200 kHz). Such a setup will be circumventing the limited temporal resolution and signal-to-noise ratio of current state-of-the-art beamlines. The experimental scheme includes the pulse compression of an ultrafast high-power Ytterbium fiber laser using the multipass cell technology, followed by the generation of ~ 3 fs UV pulses via dispersive wave emission in a gas-filled stretched hollow-core fiber.
The output of the fiber will be coupled to a high-vacuum chamber where a dispersion-free characterization of the ultrabroadband UV radiation, another important technological challenge, will be performed using an interferometric approach that was developed at the Universität Hamburg. The light source will allow UV-pump UV-probe time-resolved experiments in which the high repetition rate will be exploited for covariance spectroscopy, benefiting from high statistics. A number of applications are envisaged, notably the investigation of UV-induced dynamics in polyatomic molecules such as amino-acids and DNA bases.