Capability for Science of the Future: Ultrafast Spectroscopy Laser Centre at Sheffield, USLS

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We propose to build an ultrafast laser spectroscopy system which, by exploiting modern technological advances, will allow us to examine in many different ways what happens to molecules and materials after they absorb light, both immediately after absorption and then the longer-term consequences.The interaction of light with matter is one of the most important areas in modern science. It underpins the emerging technology of new photonics-based materials that can be used in the communications, computing, displays and lighting devices of the future; the economic impact of this technology sector in the short-to-medium term is predicted to be very large. Interaction of light with matter is also the basis of the conversion of sunlight into energy by photosynthesis - which is fundamental to life on earth. Natural photosynthesis is quite well understood and is sufficiently effective for Nature's needs: the goal now is to build artificial systems that mimic the key properties of natural photosynthetic systems so that we can, finally, harvest sunlight as an energy source and make a major contribution to mankind's long-term sustainable energy generation that is not fossil-fuel dependent and is not polluting. The tasks of artificial photosynthesis are extensive: not only do we need to construct molecular systems or materials that can capture light effectively, but they need to be able to use it to either generate energy directly (e.g. as electricity in photovoltaic cells), or to drive chemical reactions that provide 'stored energy' as a solar fuel (e.g. by providing energy for conversion of the waste-product CO2 to the fuel methanol).All research in light/matter interactions - whether it is directed at understanding nature, harnessing energy, or constructing new optical communications devices - requires the ability to measure the extremely fast changes that occur in molecules and materials immediately after light is absorbed. The initial changes take place on a timescale of femtoseconds and may involve movement of electron density, or changes in bond vibrations, which can be detected. Subsequent to this the captured energy 'flows' through the molecular assembly or material, and this movement of charge or energy from place to place - which can occur on timescales from picoseconds to microseconds - can again be visualized in detail. Finally any subsequent chemical changes that may occur on timescales as slow as milliseconds will be visualized. The result will be the ability to monitor exactly what happens in materials and molecular assemblies once the photon of light is absorbed; as the energy or an electron subsequently moves through the material and/or results in structural changes; and as the energy is finally used in various ways from luminescence to triggering chemical reactions.The facility that we will build will be unique in the UK university system as it will combine diverse aspects of ultrafast spectroscopy in a single, integrated facility which will enable the most comprehensive set of measurements possible at a single site with a single sample. The facility will combine a wide range of timescales that can be measured (all events from femtoseconds to milliseconds, which spans 11 orders of magnitude); a continuous spectrum of energies from low-energy vibrations to high-energy electronic transitions; and a wide range of interrogation techniques that allow changes in structure and electronic properties to be probed in real time. This will provide researchers both in Sheffield and the wider UK community - with whom the facility will be shared, by creating an "ultrafast hub" - access to a state-of-the-art tools for studying light-matter interactions. This will facilitate a wide range of science in areas of national importance and potentially benefit society from technological developments (such as new photonics-based materials and devices) and from cleaner and cheaper energy generation using sunlight.