Atomic interactions in supercritical fields: preliminary investigations for SPARC in-kind contributions

Project description


The goal of the present project proposal is to contribute to the above mentioned experimental programme. The knowledge of atomic structure- energy levels, transition amplitudes, oscillator strength- is needed for processes which provide theoretical information for spectroscopy. Accurate understanding and interpretation of phenomena in the presence of supercritical fields involves complementary studies on atoms and optical processes, and needs for a large data basis of atomic parameters, as well as a good knowledge of atomic processes dynamics in electromagnetic fields. A direction of this project is the use of full relativistic Dirac-Atomic R- matrix theory to study the state-selective photo recombination process in highly charged ions (HCI). These studies will provide accurate information at the borderline between atomic and nuclear physics.

Another direction of this project proposal represents the optimization and development of the theoretical and computational methods to study the atomic structure and the interaction of atoms with laser pulses. We shall extend our previous results obtained for linearly polarized fields [Phys. Rev. A 92, 033421 (2015)] and to theoretically investigate the 1s-nl inelastic scattering of fast electrons by hydrogen atoms in the presence of a circularly polarized laser field in order to elucidate the role of the laser field polarization.

We are also proposing here the study of the proof-of- principle experiment dedicated to the investigation of the fine-structure transitions in HCI at HESR. The XUV pulses (about 10 5 -10 8 photons/pulse in the range of 14-80eV) are produced by laser-induced high-order harmonic generation in gas. This radiation is monochromatized and works with high-resolution bandwidth selection. This new light source is well suited for fundamental and applied ultrafast science at HESR. In combination with the storage ring the system appears to be a suitable instrument for studies of high-energy transitions in highly charged ions. We aim to contribute designing the optical experiments taking into account the optical Doppler effect and the ionization threshold shift in the atom due to fs fundamental laser beam followed by the XUV one-photon ionization process.

As a next step we will carry out the commissioning of the experimental setup configuration which will be the XUV-storage ring coupling unit.