Triaxiality and exotic rotations at high spins inCe134

Abstract

High-spin states in 134 Ce have been investigated using the 116 Cd( 22 Ne,4n) reaction and the Gammasphere array. The level scheme has been extended to an excitation energy of ∼ 30 MeV and spin ∼ 54 . Two new dipole bands and four new sequences of quadrupole transitions were identified. Several new transitions have been added to a number of known bands. One of the strongly populated dipole bands was revised and placed differently in the level scheme, resolving a discrepancy between experiment and model calculations reported previously. Configurations are assigned to the observed bands based on Cranked Nilsson-Strutinsky calculations. A coherent understanding of the various excitations, both at low and high spins, is thus obtained supporting an interpretation in terms of coexistence of stable triaxial, highly deformed and superdeformed shapes up to very high spins. Rotations around different axes of the triaxial nucleus, and sudden changes of the rotation axis in specific configurations, are identified, further elucidating the nature of high-spin collective excitations in the A = 130 mass region.

Evolution from γ -soft to stable triaxiality in Nd136 as a prerequisite of chirality

“…At medium spin, the nuclear shape can change under the polarizing effect of unpaired nucleons resulting from broken pairs. In certain cases the triaxial shape becomes more rigid, being based on a deeper minimum of the potential energy surface, induced by the protons occupying low-orbitals in the lower part of the h 11/2 subshell, or by neutrons excited from orbitals below N = 82 to low-(h 9/2 , f 7/2 ) orbitals lying above N = 82 (see, e.g., [14,15] and references therein). In nuclei with several holes in the N = 82 shell closure, a multitude of triaxial bands have been observed in several Ce and Nd nuclei, giving strong support for the existence of stable triaxial shape up to very high spins in this mass region [14][15][16][17][18][19][20][21][22][23][24].…”

Systematic of Signature Splitting in Ce Nuclei

“…In the present investigation, the systematic study of signature splitting of the ΔI = 2 bands viz. band 4 (I π = 5 − state at 2056 keV), band 5 (I π = 6 − state at 2477 keV) in 132 Ce nucleus [7], band 4 (I π = 5 − state at 2174 keV), band 5 (I π = 6 − state at 2473keV) in 134 Ce nucleus [8], band B1 (I π =5 − state at 1979 keV), band B2 (I π = 6 − state at 2425 keV) in 136 Ce nucleus [9] (as shown in figure 1), has been carried out. The energy staggering index S(I) is plotted as function of spin 16 for band 4 and band 5 and found to be nearly constant and its value is relatively very low compartive to the neighbouring nuclei.…”

Diversity of shapes and rotations in the γ-soft 130Ba nucleus: First observation of a t-band in the A = 130 mass region

“…The first important result of the present work is the observation of the odd-spin bands S1 and S2o , of the even-spin bands S1 and S2o. There is very scarce experimental information on such odd-spin states decaying to the states of the S-bands, typically only a few levels being observed [26][27][28][29][30][31][32]. Their interpretation is often handwaving, invoking the γ-band built on the S-bands, or is completely missing.…”