X-ray techniques have been largely developed in the last few years due to their capacity to probe the electronic structure of molecules and materials. This development has led to the construction of modern synchrotrons and x-ray free electron laser (XFEL) facilities, which make it possible to perform experiments so sophisticated that they were barely imaginable a few years ago. As these experiments become more and more complex, so does their interpretation. In fact, the experimental spectra obtained nowadays at these installations are of little or no use without the corresponding theoretically calculated spectra that enable their interpretation.
Therefore, the advances seen on the experimental side need to go together with advances on the theoretical side. It is thus paramount to develop new and accurate methods that can keep up with the experimental progress.
In this talk I will present the work I did during my PhD on the development of coupled-cluster methods, considered to be among the most accurate in quantum chemistry, to simulate X-ray spectroscopy. Among the various x-ray techniques, I will focus primarily on K-edge and L-edge near-edge x-ray absorption fine structure (NEXAFS) and x-ray photo-electron spectroscopy (XPS), as well as their time-resolved (TR) variants.