β decay of semi-magic 130Cd: Revision and extension of the level scheme of 130 In

A. Jungclaus et al.; 8 págs.; 5 figs.; 3 tabs.The β decay of the semi-magic nucleus Cd130 has been studied at the RIBF facility at the RIKEN Nishina Center. The high statistics of the present experiment allowed for a revision of the established level scheme of In130 and the observation of additional β feeding to high-lying core-excited states in In130. The experimental results are compared to shell-model calculations employing a model space consisting of the full major N=50-82 neutron and Z=28-50 proton shells and the NA-14 interaction, and good agreement is found. ©2016 American Physical SocietyWe thank the staff of the RIKEN Nishina Center accelerator complex for providing stable beams with high intensities to the experiment. We acknowledge the EUROBALL Owners Committee for the loan of germanium detectors and the PreSpec Collaboration for the readout electronics of the cluster detectors. This work was supported by the Spanish Ministerio de Ciencia e Innovación under contract FPA2011-29854-C04 and the Spanish Ministerio de Economía y Competitividad under Contract No. FPA2014-57196-C5- 4-P, the Generalitat Valenciana (Spain) under Grant No. PROMETEO/2010/101, the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (NRF-2014S1A2A2028636, 2016K1A3A7A09005579), the Priority Centers Research Program in Korea (2009-0093817), OTKA Contract No. K-100835, JSPS KAKENHI (Grant No. 25247045), the European Commission through the Marie Curie Actions call FP7-PEOPLE-2011-IEF under Contract No. 300096, the US Department of Energy, Office of Nuclear Physics, under Contract No.DE-AC02-06CH11357, the STFC (UK), the “RIKEN foreign research program,” the German BMBF (No. 05P12RDCIA, No. 05P12RDNUP, and No. 05P12PKFNE), HIC for FAIR, the DFG cluster of excellence “Origin and Structure of the Universe,” and DFG (Contract No. KR2326/2-1).Peer Reviewe

Possible double-octupole phonon band in U238

The level scheme of U238 has been extended using the so-called unsafe Coulomb excitation technique. One positive-parity band was uncovered for the first time, and its most important features can be related to a double-octupole phonon excitation. This band decays to the known K=0 octupole band via E1 transitions, with strengths much larger than those to the ground-state band. It also decays to the K=1 and 2 octupole bands. Comparisons among the proposed zero-, one-, and two-phonon bands in U238 and those in Pu240 shed more light on the recently proposed concept of rotationally aligned octupole phonon condensation

Systematics of K-pi=8(-) isomers in N=74 nuclei

An isomer with a half-life of 6+/-1 mu s has been observed in the N=74 nucleus Gd-138, populated following the reaction Cd-106(Cl-35,p2n)Gd-138. Th, isomer decays via a 583 keV EI transition with a hindrance per degree of K forbiddenness, f(v)=24. This value is similar to the values measured for the N=74 isotones Nd-134 and Sm-136 but markedly different from that measured for Ba-130. This suggests that there is some change in structure across the N=74 isotones and possible explanations of this feature are discussed

Connections between high-K and low-K states in the s-process nucleus Lu176

Gamma-ray branches that connect high-K states to low-K states in the s-process nucleus Lu176 were observed, thus providing a link between the 58 Gyr, 7- ground state and the 5.3 h, 1- isomeric state. High sensitivity and unambiguous placement were achieved through the study of the decay of the 58 μs Kπ=14+ isomer using γ-γ-coincidence measurements. The large number of decay paths from the isomer provides a means of populating a broad selection of states from above, resulting, paradoxically, in higher sensitivity than in cases where low-spin input reactions are used. The out-of band decay widths important for excitation processes in stars are quantified

The 136Xe + 198Pt reaction: a detailed re-examination

We extend previous measurements of the transfer product yields in the reaction of Ec.m.=450MeV136Xe with 198Pt by measurements of the product yields using Gammasphere. By recording events occurring in beam bursts and in between beam bursts, we are able to extend the number of measured product yields from 78 to 171 nuclides. Our new data span a much wider range of Z and A than observed in previous work and when compared to theoretical predictions, these new measurements provide a more stringent and thorough test of models of multi-nucleon transfer (MNT) reactions

The influence of νh11/2 occupancy on the magnetic moments of collective 21+ states in A∼100 fission fragments

AbstractThe magnetic moments of Iπ=21+ states in even–even A∼100 fission fragments have been measured using the Gammasphere array, using the technique of time-integral perturbed angular correlations. The data are interpreted within the context of the interacting boson model (IBA2) leading to the suggestion of a strong νh11/2 component in the deformed 21+ states of this region

High-spin structures in 155Tb and signature splitting systematics of the πh11/2 bands in odd A≈160 nuclei

The reactions 152Sm(7Li,4n) at 45 MeV and 124Sn(36S,p4n) at 165 MeV were used to study high-spin states of the N590 nucleus 155Tb. Previously known bands have been greatly extended in spin (I'45\) and a new decoupled sequence was identified. Several band crossings or quasiparticle alignments have been observed in each of the structures, and as a result a configuration assignment has been given to the new band. B(M1)/B(E2) transition strength ratios have been extracted from the data and comparisons were made with theoretical predictions. A comprehensive analysis of the signature splitting in the energy levels and B(M1)/B(E2) ratios for the ph11/2 bands of the A'160 region has been performed. Possible interpretations for the observed trends in the signature splitting of these structures are discussed

α decay of 97249Bk and levels in 95245Am

α decay of 249Bk has been investigated by measuring its α and γ-ray spectra, both in singles and in coincidence modes. The α spectrum of a freshly purified 249Bk sample was measured with a high-resolution, double-focusing magnetic spectrometer. γ singles, γ-γ coincidence, and γ-α coincidence spectra were also recorded. The absolute intensity of the 327.45-keV γ ray has been determined to be (1.44±0.08)×10-5% per 249Bk decay. Assignments of previously known single-particle states were confirmed. A new rotational band was identified in the α singles spectrum and Am K x rays have been observed in its decay. This single-particle state, with an energy of 154 keV, has been assigned to the 3/2-[521] Nilsson state. This is the lowest excitation energy for this orbital in any Am nucleus. More precise energies and intensities of the 249Bk α groups and γ-ray transitions are provided

M3 and E4 K-forbidden decays of the Kπ=23/2- isomer in 177Lu

Decay of the long-lived (T1/2=160.44 d) Kπ=23/2- isomer in 177Lu was investigated using a chemically purified source and the Gammasphere array. New, high-multipolarity M3 and E4 deexcitation branches to the known Iπ=17/2- and 15/2- members of the π9/2-[514] band were discovered. The reduced hindrance factors per degree of K forbiddenness deduced for these two transitions are found to be relatively large when compared to similar decays from the Kπ=37/2- (T1/2=51.4 min) and Kπ=16+ (T1/2=31 yr) isomers in 177Hf and 178Hf, respectively. This is attributed to significant configuration changes that occur in the decay of this 177Lu isomer

Rotation-aligned isomer and oblate collectivity in Pt 196

An oblate rotational sequence, built on an aligned, two-quasineutron isomeric state has been established in Pt196. The isomer has a half-life of 7.7(7) ns and is associated with the Iπ=12+,(i13/2)2 neutron configuration. Excited states, with angular momentum generated primarily through successive nucleon alignments, have been populated through 1p transfer from Au197. The nucleus Pt196 is the most neutron-rich Pt isotope for which high-spin states, beyond the 12+ isomeric state, have been established thus far. Cranked shell model calculations have been performed to understand shape evolution with spin, and the role of nucleons occupying specific Nilsson orbitals in generating aligned angular momentum for both prolate and oblate deformations has been explored