Deep core photoelectron spectroscopic studies of atoms and molecules using hard X-rays

Electronic properties and structure of the matter play a major role in our life and in several applications. Use of different spectroscopic techniques provides fascinating avenues for a better understanding of these properties. One of these techniques used in this thesis is known as electron spectroscopy. It is especially suited to study different processes resulting from photo-matter interaction, such as photoabsorption, photoexcitation, photoionization, fluorescence and Auger decay via the measurement of kinetic energies and intensities of ejected electrons.

Nowadays, the availability of hard x-ray synchrotron radiation has opened new avenues in gas-phase atomic and molecular photoelectron spectroscopy. The possibility to create a very deep core hole via single-photon excitation enables studies of multitudes of interesting phenomena, like ultrafast electronic and molecular dynamics in sub-femtoseconds time scale.

In this thesis, the focus was put on the use hard x-rays as a source of excitation for the investigation of the deep core orbitals in atoms and molecules such as iodine in CH3I and CF3I molecules, krypton, and bromine in HBr molecule. The recorded electron spectra revealed different relaxation processes, which were interpreted with aid of theoretical relativistic atomic and molecular frameworks (MCDF/DF theory), Relativistic effects and quantum electrodynamic corrections were found to be crucial for a precise interpretation of the data.