Computational X-ray Spectroscopy

近年来，x射线光源的进步导致了对x射线区域光谱学的兴趣的复苏，x射线自由电子激光器的发展，可以提供短飞秒的硬x射线脉冲，为时间分辨x射线吸收测量开辟了新的前景，有望在原子水平上分辨超快化学过程。这些技术的化学选择性使其成为理想的局部探针，提供了局部几何结构和给定原子周围的电子环境。利用这些技术的许多研究的一个共同方面是使用计算模拟来解释和分析实验数据。这导致了对x射线光谱定量精确计算的迫切需要，这种计算可以应用于广泛的问题。然而，在x射线区域模拟光谱的方法的发展落后于能够处理紫外区域光谱的可比方法，目前还没有可用的软件能够为广泛的系统提供定量准确的x射线吸收和发射光谱。本提案旨在通过在时间相关密度泛函理论框架内开发专门设计的x射线吸收和发射光谱计算功能来重新解决这种平衡。这将导致软件能够提供x射线吸收和发射光谱的精确模拟，可以应用于非专业用户可以使用的各种系统，并且能够处理非常大的分子和过渡金属元素的激发。工作的补充链将是利用开发的技术来解决关键感兴趣的系统，包括液态水的x射线光谱测量的解释，离子液体和光激发过渡金属配合物的皮秒x射线吸收光谱。该项目的这一方面将通过诺丁汉化学学院资助的博士奖学金来实现。

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.