Characterization of anomalies in nuclear forward scattering under XFEL conditions

Mössbauer spectroscopy is well-established as a method to study material properties and nuclear environments of solids. One of the most common Mössbauer isotopes is 57Fe with nuclear excitation energies in the x-ray regime. With the advent of x-ray free electron lasers (XFELs), the availability of extremely brilliant and highly coherent x-ray beams has opened up new grounds of research, including Mössbauer science under previously inaccessible conditions. Recent experiments at the European XFEL (EuXFEL) facility in Schenefeld, have revealed unexpected behavior and deviations from synchrotron physics. A dedicated beamtime to investigate these anomalies was conducted in Spring 2025 at the EuXFEL. This thesis aims to systematically analyze the collected data from the beamtime and develop an understanding of the observed anomalies, to provide a foundation for further research. We will systematically analyze data from time spectrum measurements and angular scans in different experimental configurations, and discuss dependencies on various parameters. Fit models will be discussed for both types of measurements, and the results will be used to draw quantitative conclusions about the anomalies. As a key result, various degrees of freedom in the experimental setup are tested and subsequently reduced to a few parameters relevant to the anomalies. Different aspects of the anomalies are investigated by considering different samples and analysis methods. This will provide crucial insights into the character of the anomalies and may open new perspectives for investigating XFEL-induced dynamics using Mössbauer spectroscopy.