A ‘year-2008’ set of nuclear quadrupole moments, Q, is presented. Compared to the previous, ‘year-2001’ set, a major revision of the value or an improvement of the accuracy is reported for 38Sr, 49In, 50Sn (Mossbauer state), 51Sb, 57La, 80Hg and 88Ra. Slight improvements or valuable reconfirmations exist for 7N, 11Na, 13Al, 53I, 56Ba and 71Lu.

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Year-2008 nuclear quadrupole moments

Radiative lifetimes, accurate in most cases to ±5%, from time-resolved laser-induced fluorescence measurements on a slow beam of lanthanum ions are reported for 31 odd-parity levels of La II. Experimental branching fractions for La II from emission spectra covering the near-ultraviolet to the near-infrared are also reported. The spectra were recorded using the US National Solar Observatory 1.0 m Fourier transform spectrometer. The branching fractions are combined with the radiative lifetimes to produce 84 experimentally determined transition probabilities or oscillator strengths, generally accurate to ±10%, for La II. These new experimental results are compared to older experimental and theoretical results. These data are applied to determine a new value for the solar photospheric lanthanum abundance, (La) = 1.13, with estimated internal errors of ±0.03 and external errors of ±0.03.

Experimental Radiative Lifetimes, Branching Fractions, and Oscillator Strengths for La II and a New Determination of the Solar Lanthanum Abundance

The many-body perturbation theory (MBPT) is reviewed and applied to the atomic hyperfine interaction. Graphical methods are introduced by without mathematical details. The results are interpreted in terms of effective operators. For systems with a single valence electron-such as the alkali atoms-this operator has the same form as the ordinary hyperfine operator and is identical to the operator commonly used in the analysis of experimental hyperfine data. The origin of different contributions to this operator is discussed. Numerical results are given for the 22S and 22P states of the lithium atom, where accurate MBPT calculations have recently been performed. For systems with several valence electrons additional parameters are needed or, alternatively, the parameters of the one-body effective operator are allowed to be term-dependent. Recent experiments and corresponding theoretical investigations on alkaline-earth elements, with two valence electrons, are reviewed and, in particular, MBPT calculations on the calcium atom are discussed.

https://iopscience.iop.org/article/10.1088/0034-4885/47/4/001/pdf

Effective operators in the atomic hyperfine interaction

A collective S and D nucleon pair approximation of the shell model is applied to even-even Sn, Te, Xe, Ba, and Ce isotopes with mass number A ∼120–150 and neutron number ranging from 74 to 90. Our Hamiltonian employs monopole pairing, quadrupole pairing plus quadrupole-quadrupole-type interactions between like valence nucleons and quadrupole-quadrupole interactions between valence neutrons and valence protons. With very few parameters, the low-lying states of even-even Sn, Te, Xe, Ba, and Ce isotopes are well described. The calculated B(E2) values and g factors are consistent with recent experimental data. Our systematic calculations also predict B(E2) values and g factors (in particular, for nuclei with valence neutrons in the 82–126 region) if these data are not available.

Systematic calculations of low-lying states of even-even nuclei within the nucleon pair approximation

The hyperfine structure constants A and B of all139La II even levels with 5d2 and 5d6s configurations have been measured, mainly by high-resolution spectroscopy on collinear laser-ion-beams. Morover some A and B constants of odd-parity levels have been obtained.

Measurements of the hyperfine structure constants of all the 5d2 and 5d6s levels in139La II using the high-resolution spectroscopy on collinear laser-ion-beams

The hyperfine structures (hfs) of the levels of the 5d
2 and 5d6s configurations of La II, recently measured very accurately by Hohle, Huhnermann and Wagner, are interpreted in the classical parametric scheme. For the magnetic part, the contribution of the two-body far-configuration-mixing effects is determined accurately from the hfs of four levels, and compared with an ab-initio evaluation. For the electric part, all three 5d parameters are determined. The Sternheimer corrections to the radialr
−3 integral are computed by the Multiconfigurational-Hartree-Fock method, and a corrected value of the electric-quadrupole nuclear moment is deduced:Q(139La)=0.20(1) 10−24 cm2.

K. Guidara

Papers

Interpretation of the Hyperfine Structures in the Low Even Configurations of Lanthanum II