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Se from combined conversion-electron and 
-ray spectroscopySmallcombe, J.; Garnsworthy, A. B.*; Korten, W.*; Singh, P.*; Muir, D.*; Pr
chniak, L.*; Ali, F. A.*; Andreoiu, C.*; Ansari, S.*; Ball, G. C.*; et al.
Physical Review C, 110(2), p.024318_1 - 024318_16, 2024/08
被引用回数：0 パーセンタイル：0.00(Physics, Nuclear)In the selenium isotopes various shape phenomena are present, in particular the emergence of a dominant oblate deformation in the most neutron-deficient isotopes has been observed. The scenario of shape coexisting oblate and prolate bands has been proposed across the isotopic chain, with the crossing point of such bands being located near Se, where no coexistence has yet been identified. To determine the presence or absence of any low-lying 
state in Se, confirm the level structure, and interpret the nuclear deformation with theoretical models. A combined internal conversion electron and -ray spectroscopy study was undertaken with the SPICE and TIGRESS spectrometers at the TRIUMF-ISAC-II facility. Nuclear models were provided by the Generalised Triaxial Rotor Model (GTRM) and the collective Generalised Bohr Hamiltonian (GBH). Despite a comprehensive search, no evidence was found for the existence of a state below 2 MeV in Se. Significant discrepancies to the previously established positive parity level scheme were found. GBH calculations using UNEDF1 mass parameters were found to reproduce the revised low-lying level structure well. Se does not have a well defined axial shape. The 2
state at 1601 keV resembles a quasi- excitation rather than a member of a shape coexisting band; the presence of such a band is all but ruled out.
0 transition strength for 
Se using the SPICE spectrometerSmallcombe, J.; Garnsworthy, A. B.*; Korten, W.*; Singh, P.*; Ali, F. A.*; Andreoiu, C.*; Ansari, S.*; Ball, G. C.*; Barton, C. J.*; Bhattacharjee, S. S.*; et al.
Physical Review C, 106(1), p.014312_1 - 014312_9, 2022/07
被引用回数：5 パーセンタイル：64.05(Physics, Nuclear)The selenium isotopes lie at the heart of a tumultuous region of the nuclear chart where shape coexistence effects grapple with neutron-proton pairing correlations, triaxiality, and the impending proton dripline. In this work a study of Se by internal conversion electron and -ray spectroscopy was undertaken with the SPICE and TIGRESS arrays. New measurements of the branching ratio and lifetime of the 
state were performed yielding a determination of 
milliunits. Two state mixing calculations were performed that highlighted the importance of interpretation of such 
strength values in the context of shape-coexistence.
-spectroscopy at an intense cold neutron beam facilityJentschel, M.*; Blanc, A.*; de France, G.*; K
ster, U.*; Leoni, S.*; Mutti, P.*; Simpson, G.*; Soldner, T.*; Ur, C.*; Urban, W.*; et al.
Journal of Instrumentation (Internet), 12(11), p.P11003_1 - P11003_33, 2017/11
被引用回数：43 パーセンタイル：85.09(Instruments & Instrumentation)A highly efficient array of high-purity germanium (HPGe) detectors was developed and operated at the cold neutron beam facility PF1B of the Institut Laue-Langevin (ILL) to carry out nuclear structure studies, via measurements of -rays following neutron-induced capture and fission reactions. The setup consisted of a collimation system producing a pencil beam with a thermal capture equivalent flux of about 10
ns
cm
at the target position and negligible neutron halo. The target was surrounded by an array of eight to ten anti-Compton shielded EXOGAM Clover detectors, four to six anti-Compton shielded large coaxial GASP detectors and two standard Clover detectors. For a part of the campaign the array was combined with 16 LaBr
:(Ce) detectors from the FATIMA collaboration.
isobars from the 
island of inversionMorales, A. I.*; Benzoni, G.*; Watanabe, H.*; 角田 佑介*; Otsuka, T.*; 西村 俊二*; Browne, F.*; Daido, R.*; Doornenbal, P.*; Fang, Y.*; et al.
Physics Letters B, 765, p.328 - 333, 2017/02
被引用回数：38 パーセンタイル：92.34(Astronomy & Astrophysics)The level schemes of neutron-rich isotopes Co and Ni were populated in the 
decay of Fe and studied using -delayed -ray spectroscopy of the decay, at the RIBF in RIKEN, Japan. The experimental results were compared to state-of-the-art shell-model calculations, and indicate a dominance of prolate deformation in the low-lying states, coexisting with spherical states. The decay of the isobars is shown to progress in accordance to a new type of shell evolution, the so-called Type II, which involves many particle-hole excitations across energy gaps.
NiMorales, A. I.*; Benzoni, G.*; Watanabe, H.*; 西村 俊二*; Browne, F.*; Daido, R.*; Doornenbal, P.*; Fang, Y.*; Lorusso, G.*; Patel, Z.*; et al.
Physical Review C, 93(3), p.034328_1 - 034328_14, 2016/03
被引用回数：26 パーセンタイル：83.77(Physics, Nuclear)Low-lying excited states in Ni have been investigated at RIKEN by studying the decay of Co to Ni. Co was separated with BigRIPS, implanted into the WaS3ABi Silicon array, and the ray measured using the EURICA spectrometer. From the analysis, 60 new -ray transitions and 21 new levels in Ni were observed. The new experimental information is compared to shell-model calculations which include neutron excitation across the 
shell. The calculations reproduce rather well the observed states, implying that a clear understanding of these low-lying excitations has been achieved.
Mn; Probing collectivity up to N=44 in Fe isotopic chainBenzoni, G.*; Morales, A. I.*; Watanabe, H.*; 西村 俊二*; Coraggio, L.*; Itaco, N.*; Gargano, A.*; Browne, F.*; Daido, R.*; Doornenbal, P.*; et al.
Physics Letters B, 751, p.107 - 112, 2015/12
被引用回数：21 パーセンタイル：77.19(Astronomy & Astrophysics)The decays of Mn have been measured at the RIBF facility at RIKEN using the EURICA spectrometer combined with an active stopper consisting of a stack of Si detectors. Half-lives and -delayed neutron emission probabilities have been extracted for these decays, together with first experimental information on excited states populated in 
Fe. The data indicate a continuously increasing deformation for Fe isotopes up to A=70, and interpreted to be due to the interplay between quadrupole correlation of specific neutron orbitals and the monopole component of the proton-neutron interaction.
Se nuclear shapes with SPICE and TIGRESSSmallcombe, J.; Garnsworthy, A. B.*; Korten, W.*; Singh, P.*; Ali, F. A.*; Andreoiu, C.*; Ansari, S.*; Ball, G. C.*; Barton, C. J.*; Bhattacharjee, S. S.*; et al.
no journal, ,
The phenomenon of shape coexistence is prevalent in the Z
34 region, with isotopes of neutron-deficient even Ge, Se and Kr each exhibiting the characteristic low-lying coexisting 0+ bands which display quadrupole deformation different to that of the ground states. In the selenium isotopes, 
Se seem to show a prolate ground structure with shape coexisting oblate excitation, while in 
Se the oblate structure appears to have become the ground state. The exact nature of the low-lying structure Se and any shape coexistence remains uncertain. Combining the Spectrometer for Internal Conversion Electrons (SPICE) with the TIGRESS HPGe Array, a full electron and gamma-ray experimental study of Se, Se was undertaken at the TRIUMF ISAC-II facility to unveil the low-lying structure of these nuclei. Details of the device and experiment will be presented, alongside the experimental results and possible structural interpretations for both isotopes.
