First-excited state g factor of Te136 by the recoil in vacuum method

Abstract

The g factor of the first 2 + state of radioactive 136 Te with two valence protons and two valence neutrons beyond double-magic 132 Sn has been measured by the Recoil in Vacuum (RIV) method. The lifetime of this state is an order of magnitude longer than the lifetimes of excited states recently measured by the RIV method in Sn and Te isotopes, requiring a new evaluation of the free-ion hyperfine interactions and methodology used to determine the g factor. The calibration data are reported and the analysis procedures are described in detail. The resultant g factor has a similar magnitude to the g factors of other nuclei with an equal number of valence protons and neutrons in the major shell. However, an unexpected trend is found in the g factors of the N = 84 isotones, which decrease from 136 Te to 144 Nd. Shell model calculations with interactions derived from the CD Bonn potential show good agreement with the g factors and E2 transition rates of 2 + states around 132 Sn, confirming earlier indications that 132 Sn is a good doubly magic core.

Emerging collectivity from the nuclear structure of Xe132 : Inelastic neutron scattering studies and shell-model calculations

“…As in Ref. [20], the effective M 1 operator applied a correction δg l (p) = 0.13 to the proton orbital g factor and quenched the spin g factors for both protons and neutrons to 70% of their bare values. (The tensor term was ignored.)…”

“…Van Isacker [2] used the N82K interaction, an empirical interaction derived for N = 82 nuclei by Kruse and Wildenthal [27]. Vogt et al [21,22] used interactions derived by Brown et al [18] based on the CD Bonn nucleonnucleon interaction, which have also proven successful in describing the electromagnetic properties of low-lying states around 132 Sn [20,28]. These same interactions, designated jj55 (or sn100pn), are employed in the calculations reported here.…”

“…Along with the new experimental data, we seek insights into the emergence of collectivity at the microscopic level in the xenon isotopes near 136 Xe through large-basis shell-model calculations. A number of shellmodel calculations have been performed for the Xe isotopes near N = 82 [2,[17][18][19][20][21][22]. Recent work includes an extensive study of nuclei around mass 130 by Teruya et al [19], calculations on 132 Xe and 134 Xe to high spin by Vogt et al [21,22], and calculations for the low-seniority states of 136 Xe by Van Isacker [2].…”

First-excited state g factors in the stable, even Ge and Se isotopes

“…Even if an absolute RIV measurement remains elusive for the stable isotopes, the present relative g factors, together with extensive studies of the relevant free-ion hy-perfine fields [21,22], make it feasible to attempt an analysis of the g factors in the neutron-rich isotopes 78,80,82 Ge based on the vacuum deorientation of angular correlations observed following Coulomb excitation [2]. Both interactions predict marked variations in the g factors between N = 46 and N = 50 that may be detectable even with a low intensity radioactive beam measurement [19].…”

“…Since the mid-2000s, there has been interest in the RIV technique [14] for measurements of nuclear g factors for short-lived ( 10 −7 s) states of Coulomb-excited radioactive-ion beams [15]. For exam-ple, it has been used to measure the excited-state g factors of several nuclides near doubly magic 132 Sn [16][17][18][19]. It has also given a precise g factor for the sd-shell nucleus 24 Mg [20], where very simple (H-like) atomic configurations are applicable.…”