167 research outputs found
Many-electron effects on the x-ray Rayleigh scattering by highly charged He-like ions
The Rayleigh scattering of x-rays by many-electron highly charged ions is
studied theoretically. The many-electron perturbation theory, based on a
rigorous quantum electrodynamics approach, is developed and implemented for the
case of the elastic scattering of (high-energetic) photons by helium-like ion.
Using this elaborate approach, we here investigate the many-electron effects
beyond the independent-particle approximation (IPA) as conventionally employed
for describing the Rayleigh scattering. The total and angle-differential cross
sections are evaluated for the x-ray scattering by helium-like Ni,
Xe, and Au ions in their ground state. The obtained results
show that, for high-energetic photons, the effects beyond the IPA do not exceed
2% for the scattering by a closed -shell.Comment: 15 pages, 11 figure
Nuclear recoil effect on the magnetic-dipole decay rates of atomic levels
The effect of finite nuclear mass on the magnetic-dipole transition
probabilities between fine-structure levels of the same term is investigated.
Based on a rigorous QED approach a nonrelativistic formula for the recoil
correction to first order in m_e/M is derived. Numerical results for
transitions of experimental interest are presented.Comment: 9 page
Level sequence and splitting identification of closely-spaced energy levels by angle-resolved analysis of the fluorescence light
The angular distribution and linear polarization of the fluorescence light
following the resonant photoexcitation is investigated within the framework of
the density matrix and second-order perturbation theory. Emphasis has been
placed on "signatures" for determining the level sequence and splitting of
intermediate (partially) overlapping resonances, if analyzed as a function of
the photon energy of the incident light. Detailed computations within the
multiconfiguration Dirac-Fock method have been performed especially for the
photoexcitation and subsequent fluorescence emission of atomic sodium. A
remarkably strong dependence of the angular distribution and linear
polarization of the fluorescence emission is found upon the level
sequence and splitting of the intermediate overlapping resonances owing to their finite lifetime
(linewidth). We therefore suggest that accurate measurements of the angular
distribution and linear polarization might help identify the sequence and small
splittings of closely-spaced energy levels, even if they can not be
spectroscopically resolved.Comment: 9 pages, 7 figure
Quantum electrodynamics of heavy ions and atoms
The present status of quantum electrodynamics (QED) theory of heavy
few-electron ions is reviewed. The theoretical results are compared with
available experimental data. A special attention is focused on tests of QED at
strong fields and on determination of the fundamental constants. A recent
progress on calculations of the QED corrections to the parity nonconserving
6s-7s transition amplitude in neutral Cs is also discussed.Comment: Talk at ICAP 2006, Innsbruck, Austri
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