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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
被引用回数:7 パーセンタイル:65.64(Physics, Nuclear)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.
Wrzosek-Lipska, K.*; Rezynkina, K.*; Bree, N.*; Zieliska, M.*; Gaffney, L. P.*; Petts, A.*; Andreyev, A. N.; Bastin, B.*; Bender, M.*; Blazhev, A.*; et al.
European Physical Journal A, 55(8), p.130_1 - 130_23, 2019/08
被引用回数:16 パーセンタイル:80.08(Physics, Nuclear)The neutron-deficient mercury isotopes serve as a classical example of shape coexistence, whereby at low energy near-degenerate nuclear states characterized by different shapes appear. The electromagnetic structure of even-mass Hg isotopes was studied using safe-energy Coulomb excitation of neutron-deficient mercury beams delivered by the REX-ISOLDE facility at CERN. The population of 0
, 2
, and 4
states was observed in all nuclei under study. Reduced
matrix elements coupling populated yrast and non-yrast states were extracted, including their relative signs. These are a sensitive probe of shape coexistence and may be used to validate nuclear models. The experimental results are discussed in terms of mixing of two different configurations and are compared with three different model calculations: the Beyond Mean Field model, the Interacting Boson Model with configuration mixing and the General Bohr Hamiltonian. Partial agreement with experiment was observed, hinting to missing ingredients in the theoretical descriptions.
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
被引用回数:6 パーセンタイル:48.12(Astronomy & Astrophysics)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
1
0
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 3.9
10
% 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.
Jentschel, M.*; Blanc, A.*; de France, G.*; Kster, 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.
Lic, R.*; Rotaru, F.*; Borge, M. J. G.*; Gr
vy, S.*; Negoita, F.*; Poves, A.*; Sorlin, O.*; Andreyev, A. N.; Borcea, R.*; Costache, C.*; et al.
Physical Review C, 95(2), p.021301_1 - 021301_6, 2017/02
被引用回数:19 パーセンタイル:78.17(Physics, Nuclear)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. N.; 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
被引用回数:19 パーセンタイル:76.35(Physics, Nuclear)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.*; M
rginean, N.*; Sotty, C. O.*; Vedia, V.*; Andreyev, A. N.; Benzoni, G.*; et al.
Physical Review C, 93(4), p.044303_1 - 044303_7, 2016/04
被引用回数:8 パーセンタイル:46.82(Physics, Nuclear)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.
Nowak, K.*; Wimmer, K.*; Hellgartner, S.*; Mcher, D.*; Bildstein, V.*; Diriken, J.*; Elseviers, J.*; Gaffney, L. P.*; Gernh
user, R.*; Iwanicki, J.*; et al.
Physical Review C, 93(4), p.044335_1 - 044335_10, 2016/04
被引用回数:20 パーセンタイル:77.65(Physics, Nuclear)The Ar(
)
Ar two-neutron transfer reaction at 2.16 MeV/u was studied at CERN using a
Ar radioactive beam and a tritium loaded radioactive target. Angular distributions for three final states were measured and based on the shape of the differential cross section an excited state at 3695 keV was identified as the first excited 0
state. The differential cross-sections for the 0
-ground state, and first excited 2
and 0
states are compared to DWBA calculations including two-step reactions through the intermediate nucleus
Ar. By comparison large scale shell model calculations using state-of-the-art effective interactions, with and without the tensor components of the interactions, it was observed that the cross-shell proton-neutron tensor interaction has measurable effects on the observables at low excitation energy in
Ar.
Bottoni, S.*; Leoni, S.*; Fornal, B.*; Raabe, R.*; Rusek, K.*; Benzoni, G.*; Bracco, A.*; Crespi, F. C. L.*; Morales, A. I.*; Bednarczyk, P.*; et al.
Physical Review C, 92(2), p.024322_1 - 024322_8, 2015/08
被引用回数:22 パーセンタイル:78.29(Physics, Nuclear)An exploratory experiment was performed at REX-ISOLDE CERN to test the potential of cluster-transfer reactions at the Coulomb barrier as a mechanism to explore the structure of exotic neutron-rich nuclei. The transfer of triton and alpha particles in a reaction of a beam of Rb onto a
Li target were studied through particle-
coincidence measurements. The results indicate that such cluster transfer reactions can be an efficient method to investigate the structure of neutron-rich nuclei at medium-high excitation energies and spins.
Gaffney, L. P.*; Robinson, A. P.*; Jenkins, D. G.*; Andreyev, A. N.; Bender, M.*; Blazhev, A.*; Bree, N.*; Bruyneel, B.*; Butler, P.*; Cocolios, T. E.*; et al.
Physical Review C, 91(6), p.064313_1 - 064313_11, 2015/06
被引用回数:11 パーセンタイル:55.72(Physics, Nuclear)Radioactive ion beams of Rn were studied by means of low-energy Coulomb excitation at REX-ISOLDE, CERN. The electric-quadrupole (E2) matrix elements connecting the first excited 2
to the ground state of these nuclei was extracted, which permits to determine the collectivity of these isotopes, which in both cases is deduced to be weak, as expected from the low-lying level-energy scheme. Comparisons were also made with beyond-mean-field model calculations and the magnitude of the transitional quadrupole moments are well reproduced.
Diriken, J.*; Patronis, N.*; Andreyev, A. N.; Antalic, S.*; Bildstein, V.*; Blazhev, A.*; Darby, I. G.*; De Witte, H.*; Eberth, J.*; Elseviers, J.*; et al.
Physical Review C, 91(5), p.054321_1 - 054321_15, 2015/05
被引用回数:10 パーセンタイル:52.68(Physics, Nuclear)Excited states up to an excitation energy of 5.8 MeV were populated in the neutron-rich isotope Ni via the
Ni(d,p) transfer reaction at REX-Isolde, CERN. In particular, single-neutron states above the N=40 sub-shell gap were populated, and the relative spectroscopic factors were extracted using distorted-wave Born approximation analysis. The positive parity g
, d
and s
neutron orbits above the shell closure are assumed to induce strong quadrupole collectivity in neutron-rich Fe and Cr isotopes. The extracted relative spectroscopic factors show that the strength of the d
orbit is mostly split over two states, hinting to substantial mixing of the neutron d
configuration with collective modes of the core. The size of the N=50 shell gap was also estimated, and found to be 2.6 MeV near
Ni, as also determined in lighter Ni isotopes.
Orlandi, R.; Mcher, D.*; Raabe, R.*; Jungclaus, A.*; Pain, S. D.*; Bildstein, V.*; Chapman, R.*; De Angelis, G.*; Johansen, J. G.*; Van Duppen, P.*; et al.
Physics Letters B, 740, p.298 - 302, 2015/01
被引用回数:28 パーセンタイル:84.14(Astronomy & Astrophysics)Single-neutron states in Zn have been populated using the reaction
Zn(d,p) at REX-Isolde, CERN. The analysis reveals that the lowest excited states in
Zn lie at approximately 1 MeV, and involve neutron orbits above the N=50 shell gap. A 5/2
configuration was assigned to the 983-keV state. Comparison with large-scale shell model calculations supports a robust neutron N=50 shell closure for
Ni. These data constitute an important step towards the understanding the magicity of
Ni and the structure of nuclei in the region.
Rgis, J.-M.*; Jolie, J.*; Saed-Samii, N.*; Warr, N.*; Pfeiffer, M.*; Blanc, A.*; Jentschel, M.*; K
ster, U.*; Mutti, P.*; Soldner, T.*; et al.
Physical Review C, 90(6), p.067301_1 - 067301_4, 2014/12
被引用回数:24 パーセンタイル:79.51(Physics, Nuclear)A smooth onset of collectivity in Kr has been determined from reported
and E(2
) values. This is in contrast to the sudden onset in even-even Zr, Mo, and Sr isotopes. Our objective was to complete the systematics by determining the
value in
Kr, which was produced by cold-neutron-induced fission of
U. The lifetime of the 2
state in
Kr was measured via the electronic
timing technique using the EXILL and FATIMA spectrometers. Based on the measured mean lifetime of
= 15(10) ps, the
value of 13
W.u. in
Kr is determined for the first time and the smooth onset of deformation in the even-even Kr isotopes beyond neutron number N=50 is confirmed.
Diriken, J.*; Patronis, N.*; Andreyev, A. N.*; Antalic, S.*; Bildstein, V.*; Blazhev, A.*; Darby, I. G.*; De Witte, H.*; Eberth, J.*; Elseviers, J.*; et al.
Physics Letters B, 736, p.533 - 538, 2014/09
被引用回数:19 パーセンタイル:72.93(Astronomy & Astrophysics)The neutron orbits , d
and s
are assumed to be responsible for the swift onset of collectivity observed in the region below
Ni. In order to gather information on the single-particle energies and spectroscopic factors of these orbitals, single-particle states in the nucleus
Ni were populated using the reaction
Ni(d,p), in inverse kinematics, at REX-ISOLDE, CERN. The new isotope was studied using combined particle-
spectroscopy. Comparison with DWBA calculations, permitted the identification of positive parity states with a substantial amount of
d
(1007 keV) and
d
(2207 and 3277 keV) single-particle strength. Comparisons with extended Shell-Model calculations was also performed to confirm the single-particle nature of these states, and to deduce general properties around
Ni.
Illana, A.*; Jungclaus, A.*; Orlandi, R.; Perea, A.*; Bauer, C.*; Briz, J. A.*; Egido, J. L.*; Gernhuser, R.*; Leske, J.*; M
cher, D.*; et al.
Physical Review C, 89(5), p.054316_1 - 054316_11, 2014/05
被引用回数:11 パーセンタイル:58.53(Physics, Nuclear)The factor of the first excited state in
Zn was measured using the transient-field technique in combination with Coulomb excitation. The experiment was ran at REX-ISOLDE, CERN, and the
-ray perturbed angular correlations were measured using 4 triple Germanium clusters of the Miniball array. The experimental result
(2
) = +0.47(14) is significant to establish the structure of the Zn isotopes near N=40. Comparison with shell-model calculations reveal that to reproduce the measured energies and B(E2) of the Zn isotopes around N=40, both the proton excitations from the
orbit and neutron excitations into the
and
orbits are essential. Furthermore, beyond-mean-field calculations reveal the need to include the triaxial degree of freedom.
Doornenbal, P.*; Reiter, P.*; Grawe, H.*; 大塚 孝治*; Al-Khatib, A.*; Banu, A.*; Beck, T.*; Becker, F.*; Bednarczyk, P.*; Benzoni, G.*; et al.
Physics Letters B, 647(4), p.237 - 242, 2007/04
被引用回数:35 パーセンタイル:86.89(Astronomy & Astrophysics)ドイツ重イオン研究所(GSI)でCaの第一励起状態
からの脱励起
線を初めて測定した。その励起エネルギーは、3015(16)keVであることがわかり、鏡像核である
Sの励起エネルギーよりも276keVも低いことがわかった。殻模型により理論的にこれら両者の構造を調べたところ、
殻を仮定した模型空間でよく説明されることがわかった。この鏡像核の大きなエネルギーのずれは、クーロン力によるトーマスエルマン効果であると考えられ、それを現象論的に取り入れた殻模型計算によりこの領域のミラー核のエネルギーシフトがよく説明されることがわかった。
Orlandi, R.; Mcher, D.*; Raabe, R.*; Jungclaus, A.*; Pain, S. D.*; Bildstein, V.*; Chapman, R.*; De Angelis, G.*; Johansen, J. G.*; Van Duppen, P.*; et al.
no journal, ,
Single-neutron states in the = 49 isotope
Zn were populated in the
Zn(d,p)
Zn transfer reaction at REX-ISOLDE, CERN. The combined detection of protons ejected in the reaction and of
rays emitted by
Zn permitted the identification of the lowest-lying 5/2
and 1/2
excited states. The analysis of proton angular distributions links these states to a significant amount of single-particle strength around 1 MeV, and specifically to the
d
and
s
neutron orbits, which lie above the
= 50 neutron shell gap. Comparison with large-scale-shell-model calculations supports a robust
= 50 shell-closure for
Ni. These data constitute a considerable step towards the understanding of the magicity of
Ni and of the structure of isotopes in the region.