9 research outputs found
Theoretical isotope shifts in neutral barium
The present work deals with a set of problems in isotope shifts of neutral
barium spectral lines. Some well known transitions
( and ) are first
investigated. Values of the changes in the nuclear mean-square charge radius
are deduced from the available experimental isotope shifts using our ab initio
electronic factors. The three sets
obtained from these lines are consistent with each other. The combination of
the available nuclear mean-square radii with our electronic factors for the
transitions produces isotope shift values in
conflict with the laser spectroscopy measurements of Dammalapati et al. (Eur.
Phys. J. D 53, 1 (2009))
Mass- and field-shift isotope parameters for the resonance doublet of lithium-like ions
It was recently shown that dielectronic recombination measurements can be
used for accurately inferring changes in the nuclear mean-square charge radii
of highly-charged lithium-like neodymium [Brandau et al., Phys. Rev. Lett. 100
073201 (2008)]. To make use of this method to derive information about the
nuclear charge distribution for other elements and isotopes, accurate
electronic isotope shift parameters are required. In this work, we calculate
and discuss the relativistic mass- and field-shift factors for the two transitions along the lithium
isoelectronic sequence. Based on the multiconfiguration Dirac-Hartree-Fock
method, the electron correlation and the Breit interaction are taken into
account systematically. The analysis of the isotope shifts for these two
transitions along the isoelectronic sequence demonstrates the importance and
competition between the mass shifts and the field shifts.Comment: Accepted by Phys. Rev.
Calculs ab initio relativistes de déplacements isotopiques
Quand les effets de la masse finie du noyau et de la distribution de charge spatiale sont pris en compte dans lâHamiltonien dĂ©crivant un systĂšme atomique, les isotopes dâun Ă©lĂ©ment, caractĂ©risĂ©s par le mĂȘme nombre de protons mais un nombre diffĂ©rent de neutrons, ont des niveaux dâĂ©nergie Ă©lectronique diffĂ©rents. Le dĂ©placement entre les niveaux dâĂ©nergie (pour un mĂȘme Ă©tat quantique) de deux isotopes diffĂ©rents est appelĂ© le dĂ©placement isotopique de niveau. De maniĂšre gĂ©nĂ©rale, on peut distinguer les dĂ©placements isotopiques de champ (field shift) et les dĂ©placements isotopiques de masse (mass shift). Pour les systĂšmes Ă plus dâun Ă©lectron, le specific mass shift (SMS) apparaĂźt. GrĂące Ă sa faible pondĂ©ration, le paramĂštre SMS peut ĂȘtre traitĂ© comme une perturbation de lâHamiltonien ;son estimation fait appel aux intĂ©grales de Vinti [5].Dans un contexte relativiste, les programmes grasp2K [2] et mcdf-gme [1] permettent de rĂ©soudre les Ă©quations de Dirac-Fock associĂ©es Ă un Ă©tat multiconfigurationnel et dâen fournir lâĂ©nergie ainsi que la reprĂ©sentation numĂ©rique des orbitales monoĂ©lectroniques. Nous avons crĂ©Ă© et introduit dans le programme mcdf-gme une sous-routine capable dâestimer les paramĂštres de masse et de champ Ă partir des fonctions dâonde multiconfigurationnelles. Pour le programme GRASP2K, un module indĂ©pendant Ă Ă©tĂ© crĂ©Ă©. Par ailleurs, un opĂ©rateur plus complet impliquant des corrections en αZ, a Ă©tĂ© dĂ©rivĂ© par Shabaev [4] et, de maniĂšre indĂ©pendante, par Palmer [3]. Nous avons dĂ©duit la forme tensorielle de cet opĂ©rateur et avons Ă©galement implĂ©mentĂ© dans les programmes citĂ©s ci-dessus le calcul de ses Ă©lĂ©ments de matrice.GrĂące Ă ces outils nous avons pu Ă©tudier la dĂ©tĂ©rioration de lâopĂ©rateur dâĂ©nergie cinĂ©tique pour estimer le normal mass shift et travailler divers systĂšmes comme le lithium neutre et sa sĂ©quence isoĂ©lectronique. Par la suite nous avons Ă©galement travaillĂ© sur les sĂ©quences isoĂ©lectroniques du bore, du bĂ©ryllium, du carbone et de lâazote. Enfin, certains effets isotopiques ont Ă©tĂ© Ă©tudiĂ©s pour plusieurs transitions dans le baryum neutre.Bibliographie[1] J. P. Desclaux. A relativistic multiconfiguration Dirac-Fock package. In E. Clementi, editor, Methods and Techniques in Computational Chemistry - vol. A :Small Systems of METTEC, page 253. STEF, Cagliari, 1993.[2] P. Jönsson, X. He, C. Froese Fischer and I. P. Grant. The GRASP2K relativistic atomic structure package. Comput. Phys. Commun. 177 :597â622, 2007.[3] C. W. P. Palmer. Reformulation of the theory of the mass shift. J. Phys. B :At. Mol. Phys. 20 :5987â5996, 1987.[4] V. M. Shabaev and A. N. Artemyev. Relativistic nuclear recoil corrections to the energy levels of multicharged ions. J. Phys. B :At. Mol. Phys. 27 :1307â1314, 1994.[5] J. P. Vinti. Isotope shift in magnesium. Phys. Rev. 56 :1120â1132, 1939.Doctorat en Sciences de l'ingĂ©nieurinfo:eu-repo/semantics/nonPublishe
Relativistic calculations on isotope shifts in barium
When the effects of the finite mass of the nucleus and the spatial nuclear charge distribution are taken into account in the Hamiltonian describing an atomic system, the isotopes of an element have different electronic energy levels. In the present work, we are investigating these mass and field effects in neutral barium, hoping to shed some light on the surprising observed deviation of isotope shifts from their expected behavior for odd isotopes in an analysis based on King-plots.info:eu-repo/semantics/publishe
Ris3: A program for relativistic isotope shift calculations
An atomic spectral line is characteristic of the element producing the spectrum. The line also depends on the isotope. The program ris3 (Relativistic Isotope Shift) calculates the electron density at the origin and the normal and specific mass shift parameters. Combining these electronic quantities with available nuclear data, isotope-dependent energy level shifts are determined. © 2013 Elsevier B.V. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
On the breakdown of the Dirac kinetic energy operator for estimating normal mass shifts
The Dirac kinetic energy (DKE) form of the normal mass shift operator (me/M âi=1N Ti), which is an approximation of the (1/2M âi=1N pi 2) operator built on the relativistic electron momenta, is widely used in relativistic atomic structure calculations. In the present paper, we illustrate the progressive breakdown of the Dirac kinetic energy form relatively to the momentum form when increasing the nuclear charge along the lithium isoelectronic sequence. Both forms are incorrect in the relativistic case but the DKE operator provides expectation values that are closer to the results obtained with the more complete relativistic recoil operator. © EDP Sciences, SocietĂ Italiana di Fisica, Springer-Verlag 2012.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Hyperfine structures and Landé gJ-factors for n=2 states in beryllium-, boron-, carbon-, and nitrogen-like ions from relativistic configuration interaction calculations
Energy levels, hyperfine interaction constants, and Landé gJ-factors are reported for n=2 states in beryllium-, boron-, carbon-, and nitrogen-like ions from relativistic configuration interaction calculations. Valence, core-valence, and core-core correlation effects are taken into account through single and double-excitations from multireference expansions to increasing sets of active orbitals. A systematic comparison of the calculated hyperfine interaction constants is made with values from the available literature. © 2014 Elsevier Inc.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Relativistic calculations of 1s2.2s.2p level splitting in Be-like Kr
info:eu-repo/semantics/publishe