Molecular frame photoelectron angular distribution as a sensitive access to electronic structure and dynamics

• Applicant: Professor Dr. Philipp Demekhin
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 492619011

The molecular frame photoelectron angular distributions (MFPADs) are known to be very sensitive probes for molecular structure and dynamics. When escaping from the ion, the emitted electrons accumulate detailed information on the target and on the dynamics of a process itself, illuminating the molecular potential from within. Given by a coherent superposition of all transition amplitudes for an emission of the electron partial continuum waves, MFPADs provide the most complete information, which is not accessible otherwise. In the last two decades, a plenty of experimental and theoretical studies have demonstrated a power of MFPADs to deeper understand different fundamental physical processes. Our group was involved in the theoretical interpretation of many relevant experiments. The proposed theoretical project aims at considering fundamental and timely applications to available angle-resolved experiments and also stimulating new experiments with simplest diatomic molecules CO, O2, and N2. In the first funding period, we have systematically studied MFPADs of secondary photoelectrons, emitted during the single-site and two-site double core hole (DCH) generation. In addition, we uncovered an influence of nondipole (retardation) effects, caused by high-energy photons, on MFPADs of high-energy photoelectrons. Finally, we systematically investigated electron emission time delays in the 1s-photoionization by linearly polarized light as a function of the electron kinetic energy and an emission angle with respect to the molecular axis. In the second funding period, we plan to theoretically consider three applications, which are currently under experimental investigation by our cooperation partners. In particular, we propose to access photoemission time-delays of fixed-in-space N2 molecules by circularly polarized light, which triggers simultaneous emission of the σ- and π- photoelectron waves. In addition, we intend to study recoil-induced asymmetry of nondipole MFPADs in the K-shell photoionization of CO molecule with 20 keV photons, where the emission side of the molecule, which receives recoil, is known. Finally, we suggest a systematic study of MFPADs of electrons, released by the Compton scattering from fixed-in-space CO molecules by 20 keV photons, as functions of the absolute value and orientation of the respective photon momentum transfer relatively to the molecular axis.

• DFG Programme: Research Grants