Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 1512.06453

$γ$-soft $^{146}$Ba and the role of non-axial shapes at N ~ 90

A. J. Mitchell·C. J. Lister·E. A. McCutchan·M. Albers·A. D. Ayangeakaa·P. F. Bertone·M. P. Carpenter·C. J. Chiara·P. Chowdhury·J. A. Clark·P. Copp·H. M. David·A. Y. Deo·B. DiGiovine·N. D'Olympia·R. Dungan·R. D. Harding·J. Harker·S. S. Hota·R. V. F. Janssens·F. G. Kondev·S. H. Liu·A. V. Ramayya·J. Rissanen·G. Savard·D. Seweryniak·R. Shearman·A. A. Sonzogni·S. L. Tabor·W. B. Walters·E. Wang·S. Zhu
View original source ↗Read source document ↗Export metadata ↓

Abstract

Low-spin states in the neutron-rich, N = 90 nuclide $^{146}$Ba were populated following $β$-decay of $^{146}$Cs, with the goal of clarifying the development of deformation in Ba isotopes through delineation of their non-yrast structures. Fission fragments of $^{146}$Cs were extracted from a 1.7-Ci $^{252}$Cf source and mass-selected using the CARIBU facility. Low-energy ions were deposited at the center of a box of thin $β$ detectors, surrounded by a high-efficiency HPGe array. The new $^{146}$Ba decay scheme now contains 31 excited levels extending up to ~2.5 MeV excitation energy, double what was previously known. These data are compared to predictions from the Interacting Boson Approximation (IBA) model. It appears that the abrupt shape change found at N = 90 in Sm and Gd is much more gradual in Ba and Ce, due to an enhanced role of the $γ$ degree of freedom.

Explore related subjects

nucl-ex

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

A. J. Mitchell, C. J. Lister, E. A. McCutchan, M. Albers, A. D. Ayangeakaa, P. F. Bertone, M. P. Carpenter, C. J. Chiara, P. Chowdhury, J. A. Clark, P. Copp, H. M. David, A. Y. Deo, B. DiGiovine, N. D'Olympia, R. Dungan, R. D. Harding, J. Harker, S. S. Hota, R. V. F. Janssens, F. G. Kondev, S. H. Liu, A. V. Ramayya, J. Rissanen, G. Savard, D. Seweryniak, R. Shearman, A. A. Sonzogni, S. L. Tabor, W. B. Walters, E. Wang, S. Zhu. 2015-12-20. $γ$-soft $^{146}$Ba and the role of non-axial shapes at N ~ 90. https://doi.org/10.1103/physrevc.93.014306

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Measurements of $γ_v p \to π^+ π^-p'$ Cross Sections with the CLAS12 Detector for $Q^2$ from 2.4-8.0 GeV$^2$ and $W$ from 1.4-2.1 GeV

This paper reports exclusive cross sections for the $ep \to e'π^+π^-p'$ reaction using the CLAS12 detector at Jefferson Laboratory. The extractions of fully integrated and nine single-differential cross sections are presented for the first time for photon virtualities $Q^2$ from 2.4 to 8.0 GeV$^2$ and center-of-mass energies $W$ from 1.4 to 2.1 GeV, which covers a large part of the nucleon resonance region. These data considerably extend the kinematic reach of previous measurements from CLAS that covered $Q^2$ up to 5.0 GeV$^2$. Exclusive $γ_v p \to π^+ π^-p'$ cross section measurements are of particular importance for the extraction of $γ_vpN^*$ resonance electrocouplings across the $N^*$ spectrum, especially in the mass range above 1.6 GeV where several resonances decay preferentially to the $ππN$ final states. The electrocouplings with extended $Q^2$ coverage expected from these new data will enable an improved understanding of the emergence of $N^*$ mass and structure in the transition from the strongly coupled toward the perturbative QCD regime.

nucl-ex↗
arXiv2026

Direct measurement of Enhanced octupole collectivity in 148Dy

Excited states in $^{148}_{~66}$Dy were populated via $β^+/EC$ decay of $^{148m}$Ho using the GRIFFIN spectrometer at the TRIUMF ISAC-I facility. A combined measurement of the mean lifetime of the $3_1^-$ level using the Generalized Centroid Difference (GCD) method and branching fraction of the $3_1^-\rightarrow0_1^+$ $γ$-ray decay has been performed. From these results, an enhanced electric octupole $B(E3;3_1^-\rightarrow0_1^+)$ transition strength of 46(3)~W.u. has been determined in $^{148}_{~66}$Dy. This is the largest measured value across the closed neutron shell at $N=82$ and provides direct evidence of enhanced octupole collectivity beyond $Z=64$. The evolution of the $B(E3; 3^-_1 \rightarrow 0^+_1)$ strength along the $N=82$ isotonic chain is compared with quasiparticle random-phase approximation (QRPA) calculations using the SkI3 and SkM$^*$ Skyrme energy-density functionals, as well as with large-scale shell-model (SM) calculations. This result extends the boundaries of enhanced octupole collectivity far from the so-called `octupole magic numbers' $Z=56$ and $N=88$.

nucl-ex↗
arXiv2026

First observation of the fine structure of the Pygmy Dipole Resonance in a nucleus away from stability via the $β^-$ decay of $^{92}$Rb to $^{92}$Sr

A comprehensive $γ$-ray spectroscopy study of excited states in $^{92}$Sr populated via $β^-$ decay of $^{92}$Rb ($J^π=0^-$, $Q_β=8095(6)$~keV) was performed with the GRIFFIN spectrometer at the Isotope Separator and Accelerator (ISAC) radioactive ion beam facility at TRIUMF. The high $γ$-ray efficiency of the GRIFFIN spectrometer combined with the intense rubidium beams produced allowed for 864 $γ$-ray transitions to be placed in the level scheme with 190 excited levels populated, most of them identified for the first time. The excitation energies of low-spin states in $^{92}$Sr are well reproduced by large-scale Shell Model calculations up to 5~MeV. The $β$-feeding intensities are in very good agreement with results from a recent study employing Modular Total Absorption Spectroscopy, indicating a significant suppression of the Pandemonium effect. The experimental picture reveals the energy level dependence of log~$ft$ values in unprecedented detail. These log~$ft$ values are well reproduced by Multiple-Commutator Model calculations that identify the features in the excited levels' wavefunctions that enable the population of high-lying levels with a low effective Q-value that belong to the Pygmy Dipole Resonance.

nucl-ex↗