Paul Scherrer Institute, Swiss Light Source, 5232 Villigen, Switzerland.
Phys Chem Chem Phys. 2010 Jun 7;12(21):5551-61. doi: 10.1039/b927033g. Epub 2010 Mar 17.
Ultrafast X-ray absorption spectroscopy is a powerful tool to observe electronic and geometric structures of short-lived reaction intermediates. The ab initio FEFF9 code is applied to simulate the Pt L(3)-edge XANES spectrum of the photocatalytic diplatinum molecule Pt(2)(P(2)O(5)H(2))(4) and the photo-induced changes that occur therein. The spectra are interpreted within a XAFS-like scattering theoretical framework (bound-continuum transitions) or in terms of a final-state local l-projected density of states (LDOS) (bound-bound transitions). By using a novel Bayesian fitting procedure, we show that the ground-state structures obtained independently from the XANES and EXAFS regions of the spectrum are in good agreement with each other. The semi-quantitative result obtained for the Pt-Pt contraction in the excited state is in line with recently published values. The improved theoretical treatment of inelastic losses has shown to result in more accurate peak positions in the above-continuum region of the spectrum which is an important prerequisite for obtaining quantitative structural information from (time-resolved) XANES spectra.
飞秒 X 射线吸收光谱是一种强大的工具，可用于观察短寿命反应中间体的电子和几何结构。从头算 FEFF9 代码被应用于模拟光催化双铂分子Pt(2)(P(2)O(5)H(2))(4)的 Pt L(3)-边 XANES 光谱及其在其中发生的光诱导变化。光谱在 XAFS 样散射理论框架内（束缚-连续态跃迁）或在最终态局部 l-投影态密度（LDOS）（束缚-束缚态跃迁）的基础上进行解释。通过使用新的贝叶斯拟合程序，我们表明从光谱的 XANES 和 EXAFS 区域独立获得的基态结构彼此吻合良好。对于激发态中 Pt-Pt 收缩的半定量结果与最近发表的值一致。对非弹性损耗的改进理论处理已显示出在光谱的上连续区中导致更准确的峰位置，这是从（时间分辨）XANES 光谱获得定量结构信息的重要前提。
