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Spherical-oblate shape coexistence in $^{94}$Zr from a model-independent analysis
Authors:
N. Marchini,
M. Rocchini,
M. Zielinska,
A. Nannini,
D. T. Doherty,
N. Gavrielov,
P. E. Garrett,
K. Hadynska-Klek,
A. Goasduff,
D. Testov,
S. D. Bakes,
D. Bazzacco,
G. Benzoni,
T. Berry,
D. Brugnara,
F. Camera,
W. N. Catford,
M. Chiari,
F. Galtarossa,
N. Gelli,
A. Gottardo,
A. Gozzelino,
A. Illana,
J. Keatings,
D. Mengoni
, et al. (11 additional authors not shown)
Abstract:
Low-lying states of $^{94}$Zr were investigated via low-energy multi-step Coulomb excitation. From the measured $γ$-ray yields, 13 reduced transition probabilities between low-spin states were determined, together with the spectroscopic quadrupole moments of the $2_{1,2}^+$ states. Based on this information, for the first time in the Zr isotopic chain, the shapes of the $0_{1,2}^+$ states includin…
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Low-lying states of $^{94}$Zr were investigated via low-energy multi-step Coulomb excitation. From the measured $γ$-ray yields, 13 reduced transition probabilities between low-spin states were determined, together with the spectroscopic quadrupole moments of the $2_{1,2}^+$ states. Based on this information, for the first time in the Zr isotopic chain, the shapes of the $0_{1,2}^+$ states including their deformation softness were inferred in a model-independent way using the quadrupole sum rules approach. The ground state of $^{94}$Zr possesses a rather diffuse shape associated with a spherical configuration, while the $0_2^+$ state is oblate and more strongly deformed. The observed features of shape coexistence in $^{94}$Zr are in agreement with Monte-Carlo shell-model predictions, and the present results are vital to refine the IBM-CM description of the Zr isotopes around $A\approx 100$ in terms of an intertwined quantum phase transition.
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Submitted 13 August, 2024;
originally announced August 2024.
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Shape coexistence in the neutron-deficient $^{188}$Hg investigated via lifetime measurements
Authors:
M. Siciliano,
I. Zanon,
A. Goasduff,
P. R. John,
T. R. Rodríguez,
S. Péru,
I. Deloncle,
J. Libert,
M. Zielińska,
D. Ashad,
D. Bazzacco,
G. Benzoni,
B. Birkenbach,
A. Boso,
T. Braunroth,
M. Cicerchia,
N. Cieplicka-Oryńczak,
G. Colucci,
F. Davide,
G. de Angelis,
B. de Canditiis,
A. Gadea,
L. P. Gaffney,
F. Galtarossa,
A. Gozzelino
, et al. (19 additional authors not shown)
Abstract:
Shape coexistence in the $Z \approx 82$ region has been established in mercury, lead and polonium isotopes. Even-even mercury isotopes with $100 \leq N \leq 106$ present multiple fingerprints of this phenomenon, which seems to be no longer present for $N \geq 110$. According to a number of theoretical calculations, shape coexistence is predicted in the $^{188}$Hg isotope. The $^{188}$Hg nucleus wa…
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Shape coexistence in the $Z \approx 82$ region has been established in mercury, lead and polonium isotopes. Even-even mercury isotopes with $100 \leq N \leq 106$ present multiple fingerprints of this phenomenon, which seems to be no longer present for $N \geq 110$. According to a number of theoretical calculations, shape coexistence is predicted in the $^{188}$Hg isotope. The $^{188}$Hg nucleus was populated using two different fusion-evaporation reactions with two targets, $^{158}$Gd and $^{160}$Gd, and a beam of $^{34}$S, provided by the Tandem-ALPI accelerators complex at the Laboratori Nazionali di Legnaro. The channels of interest were selected using the information from the Neutron Wall array, while the $γ$ rays were detected using the GALILEO $γ$-ray array. The lifetimes of the excited states were determined using the Recoil Distance Doppler-Shift method, employing the dedicated GALILEO plunger device. Using the two-bands mixing and rotational models, the deformation of the pure configurations was obtained from the experimental results. The extracted transition strengths were compared with those calculated with the state-of-the-art symmetry-conserving configuration-mixing (SCCM) and five-dimentional collective Hamiltonian (5DCH) approaches in order to shed light on the nature of the observed structures in the $^{188}$Hg nucleus. An oblate, a normal- and a super-deformed prolate bands were predicted and their underlying shell structure was also discussed.
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Submitted 22 February, 2020; v1 submitted 24 January, 2020;
originally announced January 2020.
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Non-Symmetrized Hyperspherical Harmonics Method for Non-Equal Mass Three-Body Systems
Authors:
A. Nannini,
L. E. Marcucci
Abstract:
The non-symmetrized hyperspherical harmonics method for a three-body system, composed by two particles having equal masses, but different from the mass of the third particle, is reviewed and applied to the $^3$H, $^3$He nuclei and $^3_Λ$H hyper-nucleus, seen respectively as $nnp$, $ppn$ and $NNΛ$ three-body systems. The convergence of the method is first tested in order to estimate its accuracy. T…
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The non-symmetrized hyperspherical harmonics method for a three-body system, composed by two particles having equal masses, but different from the mass of the third particle, is reviewed and applied to the $^3$H, $^3$He nuclei and $^3_Λ$H hyper-nucleus, seen respectively as $nnp$, $ppn$ and $NNΛ$ three-body systems. The convergence of the method is first tested in order to estimate its accuracy. Then, the difference of binding energy between $^3$H and $^3$He due to the difference of the proton and the neutron masses is studied using several central spin-independent and spin-dependent potentials. Finally, the $^3_Λ$H hypernucleus binding energy is calculated using different $NN$ and $ΛN$ potential models. The results have been compared with those present in the literature, finding a very nice agreement.
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Submitted 19 October, 2018; v1 submitted 6 September, 2018;
originally announced September 2018.
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The mutable nature of particle-core excitations with spin in the one-valence-proton nucleus 133Sb
Authors:
G. Bocchi,
S. Leoni,
B. Fornal,
G. Colo',
P. F. Bortignon,
S. Bottoni,
A. Bracco,
C. Michelagnoli,
D. Bazzacco,
A. Blanc,
G. De France,
M. Jentschel,
U. Koster,
P. Mutti,
J. -M. Regis,
G. Simpson,
T. Soldner,
C. A. Ur,
W. Urban,
L. M. Fraile,
R. Lozeva,
B. Belvito,
G. Benzoni,
A. Bruce,
R. Carroll
, et al. (21 additional authors not shown)
Abstract:
The gamma-ray decay of excited states of the one-valence-proton nucleus 133Sb has been studied using cold-neutron induced fission of 235U and 241Pu targets, during the EXILL campaign at the ILL reactor in Grenoble. By using a highly efficient HPGe array, coincidences between gamma-rays prompt with the fission event and those delayed up to several tens of microseconds were investigated, allowing to…
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The gamma-ray decay of excited states of the one-valence-proton nucleus 133Sb has been studied using cold-neutron induced fission of 235U and 241Pu targets, during the EXILL campaign at the ILL reactor in Grenoble. By using a highly efficient HPGe array, coincidences between gamma-rays prompt with the fission event and those delayed up to several tens of microseconds were investigated, allowing to observe, for the first time, high-spin excited states above the 16.6 micros isomer. Lifetimes analysis, performed by fast-timing techniques with LaBr3(Ce) scintillators, reveals a difference of almost two orders of magnitude in B(M1) strength for transitions between positive-parity medium-spin yrast states. The data are interpreted by a newly developed microscopic model which takes into account couplings between core excitations (both collective and non-collective) of the doubly magic nucleus 132Sn and the valence proton, using the Skyrme effective interaction in a consistent way. The results point to a fast change in the nature of particle-core excitations with increasing spin.
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Submitted 25 March, 2016;
originally announced March 2016.