arXiv subjects

Yuri A. Litvinov

Publications and source records attributed to Yuri A. Litvinov.

23 records · Page 2Linked to original sources

arXiv2014

Dominant Secondary Nuclear Photoexcitation with the X-ray Free Electron Laser

The new regime of resonant nuclear photoexcitation rendered possible by x-ray free electron laser beams interacting with solid state targets is investigated theoretically. Our results unexpectedly show that secondary processes coupling nuclei to the atomic shell in the created cold high-density plasma can dominate direct photoexcitation. As an example we discuss the case of $^{93m}$Mo isomer depletion for which nuclear excitation by electron capture as secondary process is shown to be orders of magnitude more efficient than the direct laser-nucleus interaction. General arguments revisiting the role of the x-ray free electron laser in nuclear experiments involving solid-state targets are further deduced.

nucl-th↗

arXiv2014

SPARC Collaboration: New Strategy for Storage Ring Physics at FAIR

SPARC collaboration at FAIR pursues the worldwide unique research program by utilizing storage ring and trapping facilities for highly-charged heavy ions. The main focus is laid on the exploration of the physics at strong, ultra-short electromagnetic fields including the fundamental interactions between electrons and heavy nuclei as well as on the experiments at the border between nuclear and atomic physics. Very recently SPARC worked out a realization scheme for experiments with highly-charged heavy-ions at relativistic energies in the High-Energy Storage Ring HESR and at very low-energies at the CRYRING coupled to the present ESR. Both facilities provide unprecedented physics opportunities already at the very early stage of FAIR operation. The installation of CRYRING, dedicated Low-energy Storage Ring (LSR) for FLAIR, may even enable a much earlier realisation of the physics program of FLAIR with slow anti-protons.

physics.acc-ph↗

arXiv2013

Measurements of neutron-induced reactions in inverse kinematics

Neutron capture cross sections of unstable isotopes are important for neutron induced nucleosynthesis as well as for technological applications. A combination of a radioactive beam facility, an ion storage ring and a high flux reactor would allow a direct measurement of neutron induced reactions over a wide energy range on isotopes with half lives down to minutes.

nucl-ex↗

arXiv2013

Hyperfine-induced effects on the linear polarization of the K$α_1$ emission from helium-like ions

The linear polarization of the characteristic photon emission from few-electron ions is studied for its sensitivity with regard to the nuclear spin and magnetic moment of the ions. Special attention is paid, in particular, to the K$α_1$ ($1s 2p_{3/2} ^{1,3}P_{1,2} \to 1s^2 ^1S_0$) decay of selected helium-like ions following the radiative electron capture into initially hydrogen-like species. Based on the density matrix theory, a unified description is developed that includes both, the many-electron and hyperfine interactions as well as the multipole-mixing effects arising from the expansion of the radiation field. It is shown that the polarization of the K$α_1$ line can be significantly affected by the mutipole mixing between the leading $M2$ and hyperfine-induced $E1$ components of $1s2p ^3P_2, F_i \to 1s^2 ^1S_0, F_f$ transitions. This $E1$-$M2$ mixing strongly depends on the nuclear properties of the considered isotopes and can be addressed experimentally at existing heavy-ion storage rings.

nucl-th↗

arXiv2009

Can Hyperfine Excitation explain the Observed Oscillation-Puzzle of Nuclear Orbital Electron Capture of Hydrogen-like Ions?

Modulated in time orbital electron capture (EC) decays have been observed recently in stored H-like $^{140}$Pr$^{58+}$ and $^{142}$Pm$^{60+}$ ions. Although, the experimental results are extensively discussed in literature, a firm interpretation has still to be established. Periodic transitions between the hyperfine states could possible lead to the observed effect. Both selected nuclides decay to stable daughter nuclei via allowed Gamow-Teller transitions. Due to the conservation of total angular momentum, the allowed EC decay can only proceed from the hyperfine ground state of parent ions. In this work we argue that periodic transitions to the excited hyperfine state (sterile) in respect to the allowed EC decay ground state cannot explain the observed decay pattern.

nucl-th↗