Dynamic electron correlations in one- and two-center atomic systems
Final Report Abstract
We have theoretically studied a number of dynamical processes driven by one- and two-center electron correlations. Regarding one-center problems, we have developed a fully relativistic theory for electron loss from a hydrogen-like highly charged ion by electron impact for near-threshold impact energies where the interaction with the nucleus of the ion is effectively very strong that has a crucial influence on the electron motion and the electron-electron correlations. This theory, combined with a relativistic description of electron loss by proton impact, enabled us to calculate also electron loss cross sections in collisions of highly charged ions with hydrogen and helium atoms. We have moreover proposed an ab-initio relativistic QED theory for elastic electron scattering on hydrogen-like highly charged ions at electron impact energies where autoionizing states of the corresponding helium-like ion may play an important role in the process. The theory describes in a unified and self-consistent way both the direct (Coulomb) scattering and resonant scattering proceeding via formation and consequent decay of autoionizing states. Using this theory we have calculated scattering cross sections for elastic electron scattering on B4+ , Ca19+ , Fe25+ , Kr35+ , and Xe53+ . The theory was also generalized to collisions of hydrogen-like highly charged ions with atoms considering the latter as a source of (quasi)free electrons. Regarding two-center problems, we focused on the processes of photoionization and impact ionization where, in a first step, an autoionizing resonance of the two-center system is excited that afterwards decays via dynamic interatomic electron correlations. While our earlier treatment of resonant two-center photoionization (2CPI) assumed the positions of the atomic nuclei to be fixed, we have now included effects from the nuclear motion in a molecule, considering the Li-He van-der-Waals dimer as example. The nuclear motion was shown to cause a splitting of the single ’atomic’ resonance into a multiplet of resonances that arise from the various vibrational states in the electronically excited intermediate state of Li-He. Qualitatively one may say, that the nuclear motion distributes the strength of the previously examined ’atomic’ resonance over several ’molecular’ resonances. Based on our results, we explained why the resonant enhancement of photoionization due to 2CPI in Li-He is vastly larger than in He-Ne where 2CPI was experimentally observed. The remarkable reason is the close interatomic distance in He-Ne that leads to a suppression of the photoexcitation probability. Besides, we have shown that 2CPI can strongly dominate over direct ionization also in slow atomic collisions which is surprising since in the latter case the average distance between the atoms reaches tens of thousands of Angstroems. The presence of a neighboring atom was also found to enable distinct effects in electron-impact ionization. It manifests in very pronounced resonance peaks in the energy spectrum of emitted electrons, displaying an enormous enhancement as compared with the direct (single-center) impact ionization. The enhancement in Li-He is so strong that the contribution to the total cross section from an energy intervall of order 1 eV around a resonance can be doubled because of the two-center ionization pathway. Besides, by considering impact ionization of an asymmetric diatomic system by relativistic charged projectiles we have shown that significant effects are caused by the collision velocity approaching the speed of light. However, the role of the other type of relativistic effects – the retardation in the interaction between the atoms of the dimer – turned out to be very weak. In addition, we have studied in two-center systems the processes of dielectronic recombination (2CDR), resonant electron scattering, resonant double photoionization, and multiphoton 2CPI in strong laser fields. 2CDR and interatomic coulombic electron capture were also considered in slow atomic collisions. Finally, it was shown that an analogue of 2CDR can be used to form antihydrogen ions via radiative positron attachment to antihydrogen in the presence of a neigboring (matter) atom.
Publications
- Electron loss from hydrogen-like highly charged ions in collisions with electrons, protons and light atoms. J. Phys. B 51, 055204 (2018)
K. N. Lyashchenko, O. Yu. Andreev and A. B. Voitkiv
(See online at https://doi.org/10.1088/1361-6455/aaaa11) - Resonant electron scattering and dielectronic recombination in two-center atomic systems. Phys. Rev. A 98, 012710 (2018)
A. Eckey, A. Jacob, A. B. Voitkiv and C. Müller
(See online at https://doi.org/10.1103/PhysRevA.98.012710) - Dynamic two-center resonant photoionization in slow atomic collisions New J. Phys. 21, 103010 (2019)
A. B. Voitkiv, C. Müller, S. F. Zhang and X. Ma
(See online at https://doi.org/10.1088/1367-2630/ab4616) - Two-center electron-impact ionization via collisional excitation-autoionization Phys. Rev. A 100, 032702 (2019)
F. Grüll, A. B. Voitkiv and C. Müller
(See online at https://doi.org/10.1103/PhysRevA.100.032702) - Formation of H¯+ via radiative attachment of e+ to H¯+. Phys. Rev. Res. 2, 013105 (2020)
A. Jacob, S. F. Zhang, C. Müller, X. Ma and A. B. Voitkiv
(See online at https://doi.org/10.1103/PhysRevResearch.2.013105) - Interatomic-distance dependence of resonant energy-transfer phenomena. Phys. Rev. Res. 2, 033303 (2020)
F. Grüll, A. B. Voitkiv and C. Müller
(See online at https://doi.org/10.1103/PhysRevResearch.2.033303) - Influence of nuclear motion on resonant two-center photoionization. Phys. Rev. A 102, 012818 (2020)
F. Grüll, A. B. Voitkiv and C. Müller
(See online at https://doi.org/10.1103/PhysRevA.102.012818) - QED theory of elastic electron scattering on hydrogen-like ions involving formation and decay of autoionizing states. Phys. Rev. Res. 2, 013087 (2020)
K. N. Lyashchenko, D. M. Vasileva, O. Yu. Andreev and A. B. Voitkiv
(See online at https://doi.org/10.1103/PhysRevResearch.2.013087) - Single ionization of an asymmetric diatomic system by relativistic charged projectiles. Phys. Rev. A 103, 042804 (2021)
A. Jacob, C. Müller and A. B. Voitkiv
(See online at https://doi.org/10.1103/PhysRevA.103.042804)
