36 research outputs found
QED and relativistic corrections in superheavy elements
In this paper we review the different relativistic and QED contributions to
energies, ionic radii, transition probabilities and Land\'e -factors in
super-heavy elements, with the help of the MultiConfiguration Dirac-Fock method
(MCDF). The effects of taking into account the Breit interaction to all orders
by including it in the self-consistent field process are demonstrated. State of
the art radiative corrections are included in the calculation and discussed. We
also study the non-relativistic limit of MCDF calculation and find that the
non-relativistic offset can be unexpectedly large.Comment: V3, May 31st, 200
The nonrelativistic limit of Dirac-Fock codes: the role of Brillouin configurations
We solve a long standing problem with relativistic calculations done with the
widely used Multi-Configuration Dirac-Fock Method (MCDF). We show, using
Relativistic Many-Body Perturbation Theory (RMBPT), how even for relatively
high-, relaxation or correlation causes the non-relativistic limit of states
of different total angular momentum but identical orbital angular momentum to
have different energies. We show that only large scale calculations that
include all single excitations, even those obeying the Brillouin's theorem have
the correct limit. We reproduce very accurately recent high-precision
measurements in F-like Ar, and turn then into precise test of QED. We obtain
the correct non-relativistic limit not only for fine structure but also for
level energies and show that RMBPT calculations are not immune to this problem.Comment: AUgust 9th, 2004 Second version Nov. 18th, 200
Relativistic correlation correction to the binding energies of the ground configuration of Beryllium-like, Neon-like, Magnesium-like and Argon-like ions
Total electronic correlation correction to the binding energies of the
isoelectronic series of Beryllium, Neon, Magnesium and Argon, are calculated in
the framework of relativistic multiconfiguration Dirac-Fock method. Convergence
of the correlation energies is studied as the active set of orbitals is
increased. The Breit interaction is treated fully self-consistently. The final
results can be used in the accurately determination of atomic masses from
highly charged ions data obtained in Penning-trap experiments.Comment: version soumise 3/08/200
Coordinate-space approach to the bound-electron self-energy: Self-Energy screening calculation
The self-energy screening correction is evaluated in a model in which the
effect of the screening electron is represented as a first-order perturbation
of the self energy by an effective potential. The effective potential is the
Coulomb potential of the spherically averaged charge density of the screening
electron. We evaluate the energy shift due to a , ,
, or electron screening a , ,
, or electron, for nuclear charge Z in the range . A detailed comparison with other calculations is made.Comment: 54 pages, 10 figures, 4 table
Relativistic transition wavelenghts and probabilities for spectral lines of Ne II
Transition wavelengths and probabilities for several 2p4 3p - 2p4 3s and 2p4
3d - 2p4 3p lines in fuorine-like neon ion (NeII) have been calculated within
the multiconfiguration Dirac-Fock (MCDF) method with quantum electrodynamics
(QED) corrections. The results are compared with all existing experimental and
theoretical data
Dielectronic Resonance Method for Measuring Isotope Shifts
Longstanding problems in the comparison of very accurate hyperfine-shift
measurements to theory were partly overcome by precise measurements on
few-electron highly-charged ions. Still the agreement between theory and
experiment is unsatisfactory. In this paper, we present a radically new way of
precisely measuring hyperfine shifts, and demonstrate its effectiveness in the
case of the hyperfine shift of and in
. It is based on the precise detection of dielectronic
resonances that occur in electron-ion recombination at very low energy. This
allows us to determine the hyperfine constant to around 0.6 meV accuracy which
is on the order of 10%
Relativistic calculations of pionic and kaonic atoms hyperfine structure
We present the relativistic calculation of the hyperfine structure in pionic
and kaonic atoms. A perturbation method has been applied to the Klein-Gordon
equation to take into account the relativistic corrections. The perturbation
operator has been obtained \textit{via} a multipole expansion of the nuclear
electromagnetic potential. The hyperfine structure of pionic and kaonic atoms
provide an additional term in the quantum electrodynamics calculation of the
energy transition of these systems. Such a correction is required for a recent
measurement of the pion mass
Tensorial form and matrix elements of the relativistic nuclear recoil operator
Within the lowest-order relativistic approximation () and to
first order in , the tensorial form of the relativistic corrections of
the nuclear recoil Hamiltonian is derived, opening interesting perspectives for
calculating isotope shifts in the multiconfiguration Dirac-Hartree-Fock
framework. Their calculation is illustrated for selected Li-, B- and C-like
ions. The present work underlines the fact that the relativistic corrections to
the nuclear recoil are definitively necessary for getting reliable isotope
shift values.Comment: 22 pages, no figures, submitted to J. Phys.
Reference-free measurements of the 1s 2s 2p 2PO1=2;3=2 ! 1s2 2s 2S1=2 and 1s 2s 2p 4P5=2 ! 1s2 2s 2S1=2 transition energies and widths in lithiumlike sulfur and argon ions
We have measured the widths and energies of the 1s2s2p 2 P 1/2,3/2 â 1s 2 2s 2 S 1/2 transitions in lithiumlike sulfur and argon, as well as the energies of the forbidden 1s2s2p 4 P 5/2 â 1s 2 2s 2 S 1/2 M2 transition in both elements. All measurements were performed with a double-flat crystal spectrometer without the use of any reference line. The transition energy measurements have accuracies ranging from 2.3 ppm to 6.4 ppm depending on the element and line intensity. The widths and the intensity ratios of the 1s2s2p 2 P 1/2,3/2 â 1s 2 2s 2 S 1/2 lines have also been measured. These are the first reference-free measurements of transitions in core-excited lithiumlike ions, and have an accuracy comparable to the best relative measurements. We have also performed multi-configuration Dirac-Fock calculations of the widths, energies and intensity ratios. Extensive comparison between existing experimental results and theory is performed, and Bayesian techniques employed to extract the energy of the 1s 2p 2 4 P 1/2 â 1s 2 2p 2 P 1/2 transition in sulfur and identify contaminant transitions
Relativistic K shell decay rates and fluorescence yields for Zn, Cd and Hg
In this work we use the multiconfiguration Dirac-Fock method to calculate the
transition probabilities for all possible decay channels, radiative and
radiationless, of a K shell vacancy in Zn, Cd and Hg atoms. The obtained
transition probabilities are then used to calculate the corresponding
fluorescence yields which are compared to existing theoretical, semi-empirical
and experimental results