Origin of core-to-core x-ray emission spectroscopy sensitivity to structural dynamics
Origin of core-to-core x-ray emission spectroscopy sensitivity to structural dynamics
复制标题
核对核 X 射线发射光谱对结构动力学敏感性的起源
DOI：
10.1063/4.0000022
复制
发表时间：
2020
期刊：
影响因子：
--
通讯作者：
M. Lundberg
中科院分区：
文献类型：
--
作者：
M. Vacher;K. Kunnus;Mickaël G. Delcey;K. Gaffney;M. Lundberg
最近，通过Kα X射线发射光谱（XES）强度的振荡，观察到铁光敏剂激发态的相干结构动力学。了解的起源意想不到的敏感性的核心到核心的转变，结构动力学是重要的飞秒时间分辨XES方法的进一步发展，我们相信，一般必要的解释XES信号从高度非平衡结构，是无处不在的光物理学和光化学。在这里，我们使用多组态波函数计算与原子理论相结合，详细分析了发射过程。核-核跃迁对结构动力学的敏感性是由于1 s和2 p核-空穴态之间的最小能量金属-配体键距离的移动。一个关键的效应是非键3s和3 p轨道在1 s核心空穴状态下的额外收缩，这降低了电子-电子排斥并增加了金属-配体键的重叠。这种效应被认为是普遍的，特别是对具有强键的系统。3s和3 p轨道的重要作用与径向电荷和自旋密度的分析一致，并且可以与许多过渡金属络合物观察到的负化学位移相关联。XES对结构动力学的灵敏度可以通过调谐发射能谱仪来优化，其振荡高达当前系统最大强度的±4%。理论预测可用于设计实验，分离超快激发态动力学中的电子和核自由度。
Recently, coherent structural dynamics in the excited state of an iron photosensitizer was observed through oscillations in the intensity of Kα x-ray emission spectroscopy (XES). Understanding the origin of the unexpected sensitivity of core-to-core transitions to structural dynamics is important for further development of femtosecond time-resolved XES methods and, we believe, generally necessary for interpretation of XES signals from highly non-equilibrium structures that are ubiquitous in photophysics and photochemistry. Here, we use multiconfigurational wavefunction calculations combined with atomic theory to analyze the emission process in detail. The sensitivity of core-to-core transitions to structural dynamics is due to a shift of the minimum energy metal–ligand bond distance between 1s and 2p core-hole states. A key effect is the additional contraction of the non-bonding 3s and 3p orbitals in 1s core-hole states, which decreases electron–electron repulsion and increases overlap in the metal–ligand bonds. The effect is believed to be general and especially pronounced for systems with strong bonds. The important role of 3s and 3p orbitals is consistent with the analysis of radial charge and spin densities and can be connected to the negative chemical shift observed for many transition metal complexes. The XES sensitivity to structural dynamics can be optimized by tuning the emission energy spectrometer, with oscillations up to ±4% of the maximum intensity for the current system. The theoretical predictions can be used to design experiments that separate electronic and nuclear degrees of freedom in ultrafast excited state dynamics.
DOI：
10.1126/science.aam6203
发表时间：
2017-06-23
期刊：
Science (New York, N.Y.)
影响因子：
--
作者：
Mara MW;Hadt RG;Reinhard ME;Kroll T;Lim H;Hartsock RW;Alonso-Mori R;Chollet M;Glownia JM;Nelson S;Sokaras D;Kunnus K;Hodgson KO;Hedman B;Bergmann U;Gaffney KJ;Solomon EI
通讯作者：
Solomon EI