Multiconfiguration Dirac-Fock calculations of two electric quadrupole transitions in neutral barium (original) (raw)
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Physical Review A, 1999
The multiconfiguration Dirac-Fock ͑MCDF͒ model is employed to compute the hyperfine interaction constants of the 3d 2 4s 2 D 3/2 , 3d 2 4s 2 D 5/2 , 3d 3 2 G 7/2 , 3d 3 2 G 9/2 , and 3d 3 2 P 3/2 levels of titanium ion. The wave function expansions are obtained with the active space expansion method, where configuration state functions of a specific parity and J value are generated by substitutions from the reference configurations to an active set of orbitals. The active set is then increased in a systematic way, allowing the convergence of the expectation values to be achieved. The calculated electric quadrupole hyperfine constants are used to evaluate the nuclear electric quadrupole moment of isotope 49 of titanium, for which the value Qϭ0.247(11)b is found. ͓S1050-2947͑99͒04906-9͔
Physical Review C, 2021
We report the value of the electric quadrupole moment of 209 Bi extracted from the atomic data. For this, we performed electronic structure calculations for the ground 4 S o 3/2 and excited 2 P o 3/2 states of atomic Bi using the Dirac-Coulomb-Breit Hamiltonian and the Fock space coupled cluster method with single, double, and full triple amplitudes for the three-particle Fock space sector. The value of the quadrupole moment of 209 Bi, Q(209 Bi) = −418(6) mb, derived from the resulting electric field gradient values and available atomic hyperfine splittings is in excellent agreement with molecular data. Due to the availability of the hyperfine constants for unstable isotopes of Bi, current atomic calculation allows also to correct their quadrupole moments.
Nuclear quadrupole moment of 197Au from high-accuracy atomic calculations
The Journal of Chemical Physics, 2007
The electric field gradient (EFG) at the gold nucleus is calculated using a finite field approach, to make the extraction of the nuclear quadrupole moment Q from experimental nuclear quadrupole coupling constants possible. The four-component Dirac-Coulomb Hamiltonian serves as the framework, 51 of the 79 electrons are correlated by the relativistic Fock-space coupled cluster method with single and double excitations, and the contribution of the Gaunt term, the main part of the Breit interaction, is evaluated. Large basis sets (up to 26s22p18d12f8g5h uncontracted Gaussians) are employed. Energy splittings of the D5/22 and D3/22 levels, rather than level shifts, are used to extract the EFG constants, as the former remain linear with Q up to 10-5a.u., whereas the latter display significant nonlinearity even at Q =10-8a.u. Larger Q values lead to larger energy changes and better precision. Excellent agreement (0.1%) is obtained between Q values derived from D5/22 and D3/22 data. Systematic errors connected with neglecting triple and higher excitations, truncating the basis and orbital active space, and approximating the Gaunt contribution are evaluated. The final value of Q(Au197) is 521(7)mb. It is lower than the muonic 547(16)mb and agrees within error bounds with the recent value of 510(15)mb obtained from molecular calculations.
Multi-Configuration Dirac–Hartree–Fock (MCDHF) Calculations for B-Like Ions
Atoms, 2016
Relativistic configuration interaction results are presented for several B-like ions (Ge XXVIII, Rb XXXIII, Sr XXXIV, Ru XL, Sn XLVI, and Ba LII) using the multi-configuration Dirac-Hartree-Fock (MCDHF) method. The calculations are carried out in the active space approximation with the inclusion of the Breit interaction, the finite nuclear size effect, and quantum electrodynamic corrections. Results for fine structure energy levels for 1s 2 2s 2 2p and 2s2p 2 configurations relative to the ground state are reported. The transition wavelengths, transition probabilities, line strengths, and absorption oscillator strengths for 2s 2 2p-2s2p 2 electric dipole (E1) transitions are calculated. Both valence and core-valence correlation effects were accounted for through single-double multireference (SD-MR) expansions to increasing sets of active orbitals. Comparisons are made with the available data and good agreement is achieved. The values calculated using core-valence correlation are found to be very close to other theoretical and experimental values. The behavior of oscillator strengths as a function of nuclear charge is studied. We believe that our results can guide experimentalists in identifying the fine-structure levels in their future work.
Physical Review A, 2003
The relativistic coupled-cluster method is applied to calculate the magnetic dipole hyperfine constant ''A'' of the 6s 1/2 , 6p 1/2 , 6p 3/2 , and 5d 3/2 states of singly ionized barium. After the inclusion of two-body correlation effects into the computation of the hyperfine matrix elements, the accuracy of the obtained values was significantly increased compared to earlier computations. Based on these numbers and earlier calculations of the electric dipole transitions and excitation energies, an estimate for the accuracy of the ͉͓5 p 6 ͔6s 1/2 ͘ →͉͓5p 6 ͔5d 3/2 ͘ parity-nonconserving electric dipole transition amplitude is carried out. The results suggest that for the first time, to our knowledge, a precision of better than 1% is feasible for this transition amplitude.
Chemical Physics, 1993
The "B, "'B, and 'H quadrupole coupling constants of rovibrational levels of "B2H, "'B'H, and "B'H in their B 'X+ state were calculated from molecular wavefunctions which explicitly describe nuclear displacement. The electric field gradient as a function of the internuclear distance was computed by use of the multi-reference configuration interaction approach, the radial rovibrational wavefunctions were obtained by the Fourier grid Hamiltonian method. The double-minimum character of the potential is seen to markedly influence the rovibrational dependences of the boron and deuteron coupling constants. The quadrupole hyperfine structure of all vibrational levels of "B'H and 1°B2H isotopomer is essentially determined by the relatively strong boron coupling which is perturbed by the deuteron coupling.
Physical Review A, 2008
The hyperfine structure of the long-lived 5D 3/2 and 5D 5/2 levels of Ba + ion is analyzed. A procedure for extracting relatively unexplored nuclear magnetic moments ⍀ is presented. The relevant electronic matrix elements are computed in the framework of the ab initio relativistic many-body perturbation theory. Both the first-and the second-order ͑in the hyperfine interaction͒ corrections to the energy levels are analyzed. It is shown that a simultaneous measurement of the hyperfine structure of the entire 5D J fine-structure manifold allows one to extract ⍀ without contamination from the second-order corrections. Measurements to the required accuracy should be possible with a single trapped barium ion using sensitive techniques already demonstrated in Ba + experiments.