Computational X-ray Spectroscopy

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In recent years, advances in X-ray light sources have led to resurgence in interest in spectroscopy in the X-ray region, and the development of X-ray free-electron lasers that can deliver short femtosecond pulses of hard X-rays has opened up a new vista in time-resolved X-ray absorption measurements that hold the promise of resolving ultrafast chemical processes at an atomic level. The chemical selectivity of these techniques make it ideal as a local probe, providing both the local geometric structure and the electronic environment around a given atom. A common aspect of many studies exploiting these techniques is the use of computational simulations to interpret and analyse the experimental data. This has led to a pressing need for quantitatively accurate calculations of X-ray spectroscopy that can be applied to a wide spectrum of problems. However, the development of methods to simulate spectroscopy in the X-ray region has lagged behind comparable methods able to treat spectroscopy in the UV region, and currently there is no software available that is able to provide quantitatively accurate X-ray absorption and emission spectra for a wide range of systems.This proposal aims to re-address this balance through the development of specifically designed functionality for the computation of X-ray absorption and emission spectroscopies within the framework of time-dependent density functional theory. This will result in software capable of providing accurate simulations of X-ray absorption and emission spectra that can be applied to a diverse range of systems that can be used by a non-expert user and is capable of treating very large molecules and excitations from transition metal elements. A complementary strand of the work will be to exploit the techniques developed to address systems of key interest, including the interpretation of the X-ray spectroscopic measurements of liquid water, ionic liquids and picosecond X-ray absorption spectroscopy of photo-excited transition metal complexes. This aspect of the project will be enabled through the award of a PhD studentship funded by the School of Chemistry at Nottingham.