β and γ bands in N = 88 , 90, and 92 isotones investigated with a five-dimensional collective Hamiltonian based on covariant density functional theory : vibrations, shape coexistence, and superdeformation

CITATION: Majola, S. N. T. et al. 2019. β and γ bands in N=88, 90, and 92 isotones investigated with a five-dimensional collective Hamiltonian based on covariant density functional theory: Vibrations, shape coexistence, and superdeformation. Physical Review C, 100(4). doi:10.1103/PhysRevC.100.044324.The original publication is available at https://journals.aps.org/prc/A comprehensive systematic study is made for the collective β and γ bands in even-even isotopes with neutron numbers N = 88 to 92 and proton numbers Z = 62 (Sm) to 70 (Yb). Data, including excitation energies, B(E0) and B(E2) values, and branching ratios from previously published experiments are collated with new data presented for the first time in this study. The experimental data are compared to calculations using a five-dimensional collective Hamiltonian (5DCH) based on the covariant density functional theory (CDFT). A realistic potential in the quadrupole shape parameters V (β,γ ) is determined from potential energy surfaces (PES) calculated using the CDFT. The parameters of the 5DCH are fixed and contained within the CDFT. Overall, a satisfactory agreement is found between the data and the calculations. In line with the energy staggering S(I) of the levels in the 2γ + bands, the potential energy surfaces of the CDFT calculations indicate γ -soft shapes in the N = 88 nuclides, which become γ rigid for N = 90 and N = 92. The nature of the 02 + bands changes with atomic number. In the isotopes of Sm to Dy, they can be understood as β vibrations, but in the Er and Yb isotopes the 02 + bands have wave functions with large components in a triaxial superdeformed minimum. In the vicinity of 152Sm, the present calculations predict a soft potential in the β direction but do not find two coexisting minima. This is reminiscent of 152Sm exhibiting an X(5) behavior. The model also predicts that the 03 + bands are of two-phonon nature, having an energy twice that of the 02 + band. This is in contradiction with the data and implies that other excitation modes must be invoked to explain their origin.https://journals.aps.org/prc/abstract/10.1103/PhysRevC.100.044324Publisher’s versio

Six-quasiparticle isomer in Nd-140

A search for isomeric states was performed in the nucleus Nd-140(60)80 using in-beam gamma-ray spectroscopy and the Te-126(O-18,4n) reaction. Prompt and delayed gamma-ray coincidences were measured with the AFRODITE spectrometer using the pulsed beam delivered by the Separated Sector Cyclotron of iThemba LABS. One new isomer was identified, with spin-parity I-pi=20(+) and lifetime T-1/2 >= 400 ns, at an excitation energy E-x=7430 keV. The lifetime of the 10(+) isomer at E-x=3619 keV was determined to be 32.9(1.8) ns, confirming the previously reported value. The configuration of the I-pi=20(+) isomer is assigned based on configuration-dependent cranked Nilsson-Strutinsky (CNS) calculations as a state pi(d(5/2)g(7/2))(10)(+-4)circle times nu(h(11/2)(-2))(10)(+), with the spin vectors of the six holes in the Gd-146(64)82 core fully aligned

Barrier distribution for a ‘superheavy' nucleus–-nucleus collision

Large-angle quasielastic scattering has been studied in a high-Z_1Z_2 nuclear reaction of the type leading to superheavy-element production by cold fusion. We show that despite the presence of strongly dissipative channels, and the complete absence of fusion, the notion of an external barrier distribution, determined by strong coupling to collective excitations of target and projectile, is still valid. Furthermore, our method allows us to deduce some properties of the deep-inelastic processes in this system

Close near-degeneracy in a pair of four-quasiparticle bands in Tl-194

A pair of rotational bands associated with the pi h(9/2) circle times nu i(13/2)(-1) configuration at lower spins and with the pi h(9/2) circle times nu i(13/2)(-3) configuration at higher spins is found in Tl-194. The two 4-quasiparticle bands show exceptionally close near-degeneracy in the excitation energies. Furthermore close similarity is also found in their alignments and B(M1)/B(E2) reduced transition probability ratios. Such close near-degeneracy probably indicates chiral geometry in the angular momentum space. (c) 2013 Elsevier B.V. All rights reserved

From Cape to Hortobágy: the marriage of DIAMANT with AFRODITE

The DIAMANT light charged-particle detector will be coupled with the AFRODITE γ-ray spectrometer at iThemba LABS under a bilateral agreement between South Africa and Hungary. As a first step, the standalone 'Chessboard' section of DIAMANT has been integrated with AFRODITE in order to study incomplete fusion reactions instigated by beams of 13C ions incident on targets of 170Er and 176Yb. A fuller implementation of DIAMANT with AFRODITE will take place in due course

Rotational bands and chirality in

The high-spin states in 194Tl were studied using the 181Ta(18O, 5n) reaction and the AFRODITE $\gamma$ -ray spectrometer at iThemba LABS. The level scheme of 194Tl was considerably extended with several new bands. Three negative-parity 4-quasiparticle bands were observed and associated with $\pi h_{9/2}\otimes\nu i_{13/2}^{-3}$ configurations. Two of these form a candidate chiral pair with excellent near-degeneracy. In addition two new positive-parity bands were found