Soft X-ray spectroscopy and correlated many-electron dynamics of molecular systems from first principles theory

X射线光谱技术引起了相当大的关注，因为它们允许对分子和分子络合物的局部电子结构进行原子特有的探测。与理论建模相结合，它可以是一个非常有用的工具来解开吸收原子的状态及其与环境的相互作用，特别是在激光脉冲引发的动力学得到及时解析的情况下。这个项目旨在开发和实施一种通用的理论方法，用于不同类型的软X射线光谱仪，基于包括自旋-轨道耦合在内的多参考技术。重点讨论了俄歇和其他自电离过程的计算。由此，填补了一阶和二阶光子输入/光子输出和光子输入/电子输出事件统一描述的空白。这种发展将通过提供关于相互竞争的衰变通道的补充信息，使不同类型的稳态软X射线谱的联合分析更加方便和信息丰富。此外，有了所有态之间的耦合和各自的衰减率，将实施基于密度矩阵的形式来研究超快电子和自旋动力学，并找到通过改变超短脉冲特征来引导它的方法。

X-ray spectroscopic techniques attract considerable attention, because they allow for an atom-specific probe of the local electronic structure of molecules and molecular complexes. Combined with theoretical modeling, it can be a very informative tool unraveling the state of the absorbing atom and its interactions with the environment, especially when dynamics initiated by a laser pulse is resolved in time. This project aims developing and implementing a general purpose theoretical approach to different types of soft X-ray spectroscopies, based on multi-reference techniques including spin-orbit coupling. The particular focus is put on the calculations of Auger and other autoionization processes. With this, it fills in the gap in the unified description of first-order and second-order photon-in/photon-out and photon-in/electron-out events. Such a development will make the joint analysis of different types of steady-state soft X-ray spectra more convenient and informative by providing complementary information on competing decay channels. Further, having all the couplings between states and respective decay rates at hand, a density matrix-based formalism will be implemented to study ultrafast electron and spin dynamics and to find ways to steer it by changing ultrashort pulse characteristics.