16 research outputs found
Octupole correlations in the structure of O2 bands in the N=88 nuclei150Sm Gd
Knowledge of the exact microscopic structure of the 01
+ ground state and first excited 02
+ state in 150Sm is
required to understand the branching of double β decay to these states from 150Nd. The detailed spectroscopy of
150Sm and 152Gd has been studied using (α,xn) reactions and the γ -ray arrays AFRODITE and JUROGAM II.
Consistently strong E1 transitions are observed between the excited Kπ = 02
+ bands and the lowest negative
parity bands in both nuclei. These results are discussed in terms of the possible permanent octupole deformation
in the first excited Kπ = 02
+ band and also in terms of the “tidal wave” model of Frauendorf.Web of Scienc
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
Congruent band structures in
We have used the (, 2n) and (, 4n) reactions and the AFRODITE -ray spectrometer to make a comprehensive study of the nucleus 154Gd below \ensuremath 20\hbar . While the first excited 02
+ state at 681 keV is usually considered to be the head of a \ensuremath K^{\pi}=0^{+}
-vibrational band, we propose that the data are best described as two separate vacuum states, the ground state and the 681 keV level, each with its own and octupole vibrations, pairing and alignments. The implications of this finding, for understanding the structure of transitional rare-earth nuclei, are discussed
High-resolution two-proton stripping to 2p-1h 7/2
The challenge of achieving high resolution in binary reactions involving an outgoing high-energy neutron is solved by detecting the -ray decay of populated excited states in an array of escape-suppressed HPGe detectors in coincidence with fast neutrons. The selectivity of the arrangement is of the order of 1 in 1000 and is demonstrated by L = 0 two-proton stripping to 7/2- 2p-1h levels using the 59Co(3He,)61Cu reaction at E
lab = 22.5 MeV. The observed relative two-proton stripping strengths are compared with large-basis shell-model calculations
Rotational bands and chirality in
The high-spin states in 194Tl were studied using the 181Ta(18O, 5n) reaction and the AFRODITE -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 configurations. Two of these form a candidate chiral pair with excellent near-degeneracy. In addition two new positive-parity bands were found
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
Rotational structures in 196Hg
CITATION: Lawrie, J. J., et al. 2019. Rotational structures in 196Hg. Physical Review C, 100(6):064321, doi:10.1103/PhysRevC.100.064321.The original publication is available at https://journals.aps.org/prcHigh spin states in ¹⁹⁶Hg were populated in the ¹⁹⁸Pt(α,6n) reaction at 65 MeV and γ−γ coincidence measurements were performed using the AFRODITE array at iThemba LABS. The level scheme was extended and new rotational bands were observed. A new dipole band was found. The previously reported dipole band was linked to other known states. Excitation energies, spins, and parities of all bands were determined. The bands were assigned nucleon configurations based on cranked shell model calculations.https://journals.aps.org/prc/abstract/10.1103/PhysRevC.100.064321Publisher's versio