23 research outputs found
Electronic isotope shift factors for the Ir $5d^{7}6s^{2} \ ^{4}\!F_{9/2} \to (\mbox{odd},J= 9/2)$ line at 247.587 nm
We present the theoretical calculations of the electronic isotope shift
factors of the 5d^{7}6s^{2} \ ^{4}\!F_{9/2} \to (\mbox{odd},J= 9/2) line at
247.587 nm, that were recently used to extract nuclear mean square radii and
nuclear deformations of iridium isotopes [Mukai (2020)]. The
fully relativistic multiconfiguration Dirac-Hartree-Fock method and the
relativistic configuration interaction method were used to perform the atomic
structure calculations. Additional properties such as the , Land\'e factors or were employed to
ensure an adequate description of the targeted odd level.Comment: 33 page
Relativistic semiempirical-core-potential calculations in Ca, Sr, and Ba ions on Lagrange meshes
Relativistic atomic structure calculations are carried out in
alkaline-earth-metal ions using a semiempirical-core-potential approach. The
systems are partitioned into frozen-core electrons and an active valence
electron. The core orbitals are defined by a Dirac-Hartree-Fock calculation
using the grasp2k package. The valence electron is described by a Dirac-like
Hamiltonian involving a core-polarization potential to simulate the
core-valence electron correlation. The associated equation is solved with the
Lagrange-mesh method, which is an approximate variational approach having the
form of a mesh calculation because of the use of a Gauss quadrature to
calculate matrix elements. Properties involving the low-lying metastable
states of Ca, Sr, and Ba are studied, such as
polarizabilities, one- and two-photon decay rates, and lifetimes. Good
agreement is found with other theory and observation, which is promising for
further applications in alkali-like systems.Comment: 15 pages, accepted for publication in Phys. Rev.
Ab initio MCDHF calculations of the In and Tl electron affinities and their isotope shifts
We report multiconfiguration Dirac-Hartree-Fock and relativistic
configuration interaction calculations on the Thallium (Tl) electron affinity,
as well as on the excited energy levels arising from the ground configuration
of Tl. The results are compared with the available experimental values and
further validated by extending the study to its homologous, lighter element,
Indium (In), belonging to Group 13 (III.A) of the periodic table. The
calculated electron affinities of In and Tl, 383.4 and 322.8 meV, agree with
the latest measurements by within 1\%. Three bound states are
confirmed in the configuration of In while only the ground state
is bound in the configuration of Tl. The isotope
shifts on the In and Tl electron affinities are also estimated. The E2/M1
intraconfiguration radiative transition rates within 5s^25p^2 \; ^3P_{0,1,2}
of In are used to calculate the radiative lifetimes of the metastable
levels
Structural trends in atomic nuclei from laser spectroscopy of tin
Tin is the chemical element with the largest number of stable isotopes. Its complete proton shell, comparable with the closed electron shells in the chemically inert noble gases, is not a mere precursor to extended stability; since the protons carry the nuclear charge, their spatial arrangement also drives the nuclear electromagnetism. We report high-precision measurements of the electromagnetic moments and isomeric differences in charge radii between the lowest 1/2(+), 3/2(+), and 11/2(-) states in Sn117-131, obtained by collinear laser spectroscopy. Supported by state-of-the-art atomic-structure calculations, the data accurately show a considerable attenuation of the quadrupole moments in the closed-shell tin isotopes relative to those of cadmium, with two protons less. Linear and quadratic mass-dependent trends are observed. While microscopic density functional theory explains the global behaviour of the measured quantities, interpretation of the local patterns demands higher-fidelity modelling. Measurements of the hyperfine structure of chemical elements isotopes provide unique insight into the atomic nucleus in a nuclear model-independent way. The authors present collinear laser spectroscopy data obtained at the CERN ISOLDE and measure hyperfine splitting along a long chain of odd-mass tin isotopes.Peer reviewe
Computational Atomic Structures Toward Heavy Element Research
We are interested in complex electronic structures of various atomic and ionics systems. We use an ab initioapproach, the multiconfigurational Dirac-Hartree-Fock (MCDHF), to compute atomic structures and properties.We contribute in three main ways to the already existent literature: by developing and implementing originalcomputer programs, by investigating possibilities of alternative computational methodologies and strategies, andfinally by performing accurate atomic structure calculations to support other research fields, i.e. nuclear physics,astrophysics or experimental physics, through the theoretical estimation of relevant atomic data.We raise questions about the choice of the optimal orbital basis by considering finite basis sets, MCDHF orbitalbases and natural-orbital bases. We demonstrate the promising potential of the latter in the context of hyperfinestructures and hope that others will find interest in pursuing our analysis. Ultimately, our work put forward someweaknesses of the traditional optimization strategy based on the layer-by-layer optimization strategy.We also perform large-scale calculations to determine accurate atomic properties such as energy levels, hyperfinestructures, isotope shifts, transition parameters, radiative lifetimes and Landé g factors. We show through thevariety of atomic properties and atomic systems studied, the difficulty of describing, in the relativistic framework,the correlation between the spatial position of electrons due to their Coulomb repulsion.This thesis is organized in two main parts. The first one is dedicated to the theoretical and computationalbackgrounds that are needed to understand the theoretical models and the interpretation of our results. Thesecond part presents and summarizes our articles and manuscripts. They are separated in four groups, A, B, C,and D, around the themes of the atomic orbital bases, the applications to nuclear physics, the applications toastrophysics, and investigations of negative ions.Doctorat en Sciences de l'ingénieur et technologieinfo:eu-repo/semantics/nonPublishe
POLALMM : A program to compute polarizabilities for nominal one-electron systems using the Lagrange-mesh method
We present a program to compute polarizabilities of nominal one-electron systems using the Lagrange-mesh method (LMM) (Baye, 2015), that was used by Filippin et al., (2018). A semiempirical-core-potential approach is implemented, ultimately solving a Dirac-like equation by diagonalizing the corresponding Hamiltonian matrix. In order to build the core potential, the core orbitals are obtained from independent calculations using the GRASP2018 package (Fischer et al., 2019). Therefore we provide an easy-to-use interface between the GRASP2018 package and the LMM complete finite basis, allowing to switch easily from one one-electron basis to the other. Program summary: Program Title: POLALMM CPC Library link to program files: http://dx.doi.org/10.17632/6mw5gdwfkt.1 Licensing provisions: MIT license Programming language: Fortran90 Nature of problem: Determination of the dipole and quadrupole polarizabilities. Solution method: We combine a semiempirical-core-potential approach with the numerical Lagrange-mesh method to solve a Dirac-like one-electron equation [2]. The building of the core potential requires the prior knowledge of core orbitals provided by GRASP [3]. Two free parameters are optimized by fitting the computed single-electron valence energies to their experimental reference value. References: [1] The Lagrange-mesh method, D. Baye, Phys. Rep. 565 (2015) 1-107 [2] Relativistic semiempirical-core-potential calculations in Ca+, Ba+ and Sr+ ions on Lagrange meshes, L. Filippin, S. Schiffmann, J. Dohet-Eraly, D. Baye and M. Godefroid, Phys. Rev. A 97 (2018) 012506 [3] GRASP2018 - A Fortran 95 version of the General Relativistic Atomic Structure Package, C. Froese Fischer, G. Gaigalas, P. Jönsson and J. Bieroń, Comput. Phys. Commun. 237 (2019) 184-18
On the use of the Partitioned Correlation Interaction method for atomic properties
info:eu-repo/semantics/nonPublishe
Natural orbitals in multiconfiguration calculations of hyperfine-structure parameters
We are reinvestigating the hyperfine structure of sodium using a fully relativistic multiconfiguration approach. In the fully relativistic approach, the computational strategy somewhat differs from the original nonrelativistic counterpart used by P. Jönsson, Phys. Rev. A 53, 4021 (1996)PLRAAN1050-294710.1103/PhysRevA.53.4021. Numerical instabilities force us to use a layer-by-layer approach that has some broad unexpected effects. Core correlation is found to be significant and therefore should be described in an adequate orbital basis. The natural-orbital basis provides an interesting alternative to the orbital basis from the layer-by-layer approach, allowing us to overcome some deficits of the latter, giving rise to magnetic dipole hyperfine structure constant values, in excellent agreement with observations. Effort is made to assess the reliability of the natural-orbital bases and to illustrate their efficiency
On the use of the Natural Orbitals to compute the hyperfine structure of neutral sodium
info:eu-repo/semantics/nonPublishe
Relativistic semi-empirical-core-potential calculations on Ca+, Sr+ and Ba+ ions with Lagrange meshes
info:eu-repo/semantics/nonPublishe