One new pair of positive-parity chiral doublet bands have been identified in the odd-A nucleus Nd-135 which together with the previously reported negative-parity chiral doublet bands constitute a ...third case of multiple chiral doublet (M chi D) bands in the A approximate to 130 mass region. The properties of the M chi D bands are well reproduced by constrained covariant density functional theory and particle rotor model calculations. The newly observed M chi D bands in Nd-135 represents an important milestone in supporting the existence of M chi D in nuclei.
The g factor of the isomeric I=9+ bandhead of the yrast states in 128Cs is obtained from the time differential perturbed angular distribution measurement performed with the electromagnet at IPN ...Orsay. An external magnetic field of 2.146 T at the target position was attained with GAMIPE reaction chamber surrounded by four high-purity germanium detectors, of which two were low-energy photon spectrometer type. The results are in accordance with πh11/2⊗νh−111/2I=9+ bandhead assignment and are discussed in the context of chiral interpretation of the 128Cs nucleus as a composition of the odd proton, odd neutron, and even-even core with their angular momentum vectors. The obtained g-factor value was compared with predictions of the particle-rotor model. The experimental g factor corresponds to the nonchiral geometry of the isomeric bandhead. This observation indicates the existence of the chiral critical frequency in 128Cs and may explain the absence of the chiral doublet members for I<13ℏ
The nature of two high-spin bands in Nd-136 built on the two-quasiparticle configuration pi h(11/2)(2), predicted by the triaxial projected shell model as good candidates of transverse wobbling ...bands, are investigated experimentally. The mixing ratio of one Lambda I = 1 transition connecting the one-phonon and the zero-phonon wobbling bands is established from a high-statistics JuroGam II gamma-ray spectroscopy experiment by using the combined angular correlation and linear polarization method. The resulting wobbling excitation energy and ratios of reduced electromagnetic transition probabilities are in good agreement with results of a new particle-rotor model which rigidly couples the total angular momentum of two quasiparticles to a triaxial core in an orthogonal geometry, confirming thus the transverse wobbling nature of the bands.
Several new bands have been identified in Ba-130, among which there is one with band-head spin 8(+). Its properties are in agreement with the Fermi-aligned nu h(11/2)(2)523circle times 9/2(-)514 ...Nilsson configuration. This is the first observation of a two-quasiparticle t-band in the A = 130 mass region. The t-band is fed by a dipole band involving two additional h(11/2) protons. The odd-spin partners of the proton and neutron S-bands and the ground-state band at high spins are also newly identified. The observed bands are discussed using several theoretical models, total Routhians surfaces (TRS), tilted axis cranking (TAC), particle rotor model (PRM) and projected shell model (PSM), which strongly suggest the coexistence of prolate and oblate shapes polarized by rotation aligned two-proton and two-neutron configurations, as well as prolate collective rotations around axes with different orientations. With the new results, 130 Ba presents one of the best and most complete sets of collective excitations that a gamma-soft nucleus can manifest at medium and high spins, revealing a diversity of shapes and rotations for the nuclei in the A = 130 mass region.
Tilted precession bands in Nd 135 Lv, B. F.; Petrache, C. M.; Lawrie, E. A. ...
Physical review. C,
04/2021, Letnik:
103, Številka:
4
Journal Article
Recenzirano
Two new excited bands built on the πh11/2 configuration have been identified in Nd135 in addition to the known πh11/2 band. The energy spectra of the excited bands and the available electromagnetic ...transition probabilities are in good agreement with theoretical results obtained using quasiparticle-plus-triaxial-rotor model calculations. The properties of the bands identify them as tilted precession bands instead of wobbling bands. Our results give a new insight into the interpretation of the low-lying bands in odd-A mass nuclei, and can stimulate future studies to address the nuclear triaxiality.
Coulomb excitation of 74,76Zn Illana, A.; Zielińska, M.; Huyse, M. ...
Physical review. C,
10/2023, Letnik:
108, Številka:
4
Journal Article
Recenzirano
Odprti dostop
The first experiment using radioactive beams post-accelerated by the HIE-ISOLDE facility has enabled to obtain a precise set of B(E2) transition probabilities in neutron-rich 74,76Zn isotopes. The ...resulting B(E2; 2+1→0+1) values are consistent with those determined in earlier REX-ISOLDE measurements. While the B(E2; 4+1→2+1) transition probability in 76Zn is also in agreement with earlier Coulomb-excitation results, the value obtained for 74Zn is considerably lower. For the first time, a spectroscopic quadrupole moment of the 2+1 state was measured for an exotic nucleus in this mass region. A detailed comparison is presented with large-scale shell-model and Monte Carlo shell-model calculations.
The structure of neutron-rich 96,98Sr nuclei was investigated by low-energy safe Coulomb excitation of radioactive beams at the REX-ISOLDE facility, CERN, with the MINIBALL spectrometer. A rich set ...of transitional and diagonal E2 matrix elements, including those for non-yrast structures, has been extracted from the differential Coulomb-excitation cross sections. The results support the scenario of a shape transition atN = 60, giving rise to the coexistence of a highly deformed prolate and a spherical configuration in 98Sr, and are compared to predictions from several theoretical calculations. The experimental data suggest a significant contribution of the triaxal degree of freedom in the ground state of both isotopes. In addition, experimental information on low-lying states in 98Rb has been obtained.
Three nearly degenerate pairs of doublet bands are identified in 131Ba. Two of them, with positive-parity, are interpreted as pseudospin-chiral quartet bands. This is the first time that a complete ...set of chiral doublet bands built on the pseudospin partners π(d5/2,g7/2) is observed. The chiral bands with opposite parity built on 3-quasiparticle configurations are directly connected by many E1 transitions, without involving an intermediary non-chiral configuration. The observed band structures in 131Ba have been investigated by using the reflection-asymmetric particle rotor model. The energies and the electromagnetic transition ratios of the three pairs of doublet bands observed in 131Ba are reproduced and they are interpreted as chiral doublet bands with three-quasiparticle configurations. It is the first time that multiple chiral bands are observed in the presence of enhanced octupole correlations and pseudospin symmetry.
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