Brunet, M.*; Podolyk, Zs.*; Berry, T. A.*; Brown, B. A.*; Carroll, R. J.*; Lica, R.*; Sotty, Ch.*; Andreyev, A. N.; Borge, M. J. G.*; Cubiss, J. G.*; et al.
Physical Review C, 103(5), p.054327_1 - 054327_13, 2021/05
The structure of Po populated through the EC/ decay of At is investigated using -ray spectroscopy at the ISOLDE Decay Station. The presented level scheme contains 27 new excited states and 43 new transitions, as well as a further 50 previously observed rays which have been (re)assigned a position. Through the analysis using the shell model calculations approximately half of the -decay strength of At is found to proceed via allowed decay and half via first-forbidden decay. The first-forbidden transitions predominantly populate core excited states at high excitation energies, which is qualitatively understood using shell model considerations.
Dimitriou, P.*; Basunia, S*; Bernstein, L.*; Chen, J.*; Elekes, Z.*; Huang, X.*; Hurst, A.*; 飯村 秀紀; Jain, A. K.*; Kelley, J.*; et al.
EPJ Web of Conferences, 239, p.15004_1 - 15004_4, 2020/09
評価済み核構造データファイル(Evaluated Nuclear Structure Data File: ENSDF)は、原子核構造と崩壊に関する様々な実験データを全ての核種について集めて、それらの実験データの評価値を与えてある世界唯一のデータファイルである。ENSDFは定期的に更新されており、そのための評価作業は各国の評価者で分担している。評価作業を速やかに行うために、IAEAの援助の下に評価者の国際的なネットワークが組織されている。この発表では、ネットワークの最近の活動のうち、ENSDFの処理コードの開発、測定が必要とされているデータのリストの作成、インターネット版核図表の利用の拡充などについて報告する。また、核構造・崩壊データの需要が増大しているにもかかわらず、評価者が減っている問題についても述べる。
Berry, T. A.*; Podolyk, Zs.*; Carroll, R. J.*; Lic, R.*; Grawe, H.*; Timofeyuk, N. K.*; Alexander, T.*; Andreyev, A. N.; Ansari, S.*; Borge, M. J. G.*; et al.
Physics Letters B, 793, p.271 - 275, 2019/06
Gamow-Teller decay is forbidden if the number of nodes in the radial wave functions of the initial and final states is different. This = 0 requirement plays a major role in the decay of heavy neutron-rich nuclei, affecting the nucleosynthesis through the increased half-lives of nuclei on the astrophysical -process pathway below both = 50 (for 82) and = 82 (for 126). The level of forbiddenness of the = 1 10 transition has been investigated from the decay of the ground state of Hg into the single-proton-hole nucleus Tl in an experiment at the ISOLDE Decay Station. From statistical observational limits on possible -ray transitions depopulating the 0 state in Tl, an upper limit of 3.910 % was obtained for the probability of this decay, corresponding to log 8.8 within a 95% confidence limit. This is the most stringent test of the = 0 selection rule to date.
Lic, R.*; Rotaru, F.*; Borge, M. J. G.*; Grvy, S.*; Negoita, F.*; Poves, A.*; Sorlin, O.*; Andreyev, A.; Borcea, R.*; Costache, C.*; et al.
Physical Review C, 95(2), p.021301_1 - 021301_6, 2017/02
The decay of Mg was used to study the Al nucleus through spectroscopy at the Isotope Separator On-Line facility of CERN. Previous studies identified two -decaying states in Al having spin-parity assignments =4 dominated by the normal configuration (d5/2) (f7/2) and = 1 by the intruder configuration (d5/2) (d3/2)(f7/2). Their unknown ordering and relative energy have been the subject of debate for the placement of Al inside or outside the = 20 "island of inversion". We report here that the 1 intruder lies only 46.6 keV above the 4 ground state. In addition, a new half-life of =44.9(4)ms, that is twice as long as thepreviously measured 20(10) ms, has been determined for Mg. Large-scale shell-model calculations with the recently developed SDPF-U-MIX interaction are compared with the new data and used to interpret the mechanisms at play at the very border of the = 20 island of inversion.
Lund, M. V.*; Andreyev, A.; Borge, M. J. G.*; Cederkll, J.*; De Witte, H.*; Fraile, L. M.*; Fynbo, H. O. U.*; Greenlees, P. T.*; Harkness-Brennan, L. J.*; Howard, A. M.*; et al.
European Physical Journal A, 52(10), p.304_1 - 304_14, 2016/10
Beta-delayed proton emission from Mg has been measured at ISOLDE, CERN, with the ISOLDE Decay Station setup including both charged-particle and -ray detection capabilities. A total of 27 delayed proton branches were measured including seven so far unobserved. An updated decay scheme, including three new resonances above the proton separation energy in Na and more precise resonance energies, is presented. Beta-decay feeding to two resonances above the Isobaric Analogue State in Na is observed. This may allow studies of the 4032.9(2.4) keV resonance in Ne through the beta decay of Mg, which is important for the astrophysically relevant reaction O(,)Ne. Beta-delayed protons were used to obtain a more precise value for the half-life of Mg, 91.4(1.0) ms.
Lic, R.*; Mach, H.*; Fraile, L. M.*; Gargano, A.*; Borge, M. J. G.*; Mrginean, N.*; Sotty, C. O.*; Vedia, V.*; Andreyev, A.; Benzoni, G.*; et al.
Physical Review C, 93(4), p.044303_1 - 044303_7, 2016/04
The levels in Sn populated from the decay of In isomers were investigated at the ISOLDE facility of CERN using the newly commissioned ISOLDE Decay Station. The lowest 1/2 state and the 3/2 ground state in Sn are expected to have configurations dominated by the neutron (=0) and (=2) single-particle states, respectively. Consequently, these states should be connected by a somewhat slow -forbidden transition. Using fast-timing spectroscopy we have measured the half-life of the 1/2 315.3-keV state, = 19(10) ps, which corresponds to a moderately fast transition. Shell-model calculations using the CD-Bonn effective interaction, with standard effective charges and factors, predict a 4-ns half-life for this level. We can reconcile the shell-model calculations to the measured value by the renormalization of the effective operator for neutron holes.