Shape coexistence and evolution in neutron-deficient krypton isotopes

Abstract

Total Routhian Surface (TRS) calculations have been performed to investigate shape coexistence and evolution in neutron-deficient krypton isotopes 72,74,76 Kr. The ground-state shape is found to change from oblate in 72 Kr to prolate in 74,76 Kr, in agreement with experimental data. Quadrupole deformations of the ground states and coexisting 0 + 2 states as well as excitation energies of the latter are also well reproduced. While the general agreement between calculated moments of inertia and those deduced from observed spectra confirms the prolate nature of the low-lying yrast states of all three isotopes (except the ground state of 72 Kr), the deviation at low spins suggests significant shape mixing. The role of triaxiality in describing shape coexistence and evolution in these nuclei is finally discussed.

Searching for high-$K$ isomers in the proton-rich $A\sim80$ mass region

“…1 is typical for the A ≈ 80 mass region. The abundance of subshell gaps complicates the scenarios of shape coexistence [12] and yet favors the forming of quasi-particle states. In particular, in the splitting of the g 9/2 spherical subshell, two high-Ω orbitals, 7 2 [413] and 9 2 [404], dive rapidly with increased oblate deformation, giving rise to subshell gaps at Z(N ) = 36, 40.…”

“…One relevant fact is that many of the calculated nuclides are rather proton-rich and some have even not been discovered ( 76 Zr, for instance), so accumulated experimental information on them is comparatively scant. Another reason is that experimental efforts directed to this mass region have been mainly focused on the phenomenon of shape coexistence [12] and the roles that nuclei in this region play in astrophysical processes [15]. In addition, the predicted isomers are likely to be very long-lived and the gamma rays deexciting them therefore could be both delayed and subdued.…”

“…The proton-rich A ∼ 80 mass region has been under intensive studies for its intricate manifestation of shape coexistence [11,12] and importance in the rp process [13][14][15]. Incidentally, 72 Kr turns out to be another good example of shape isomerism [16,17], as distinguished from fission isomers.…”

“…Less discussed is the K isomerism in this region [18]. In fact, the relevant Nilsson diagram shows that this mass region is rich in large subshell gaps [12]. These subshell gaps not only play a decisive role in the stabilization of deformation by providing extra energy reduction in shell correction, but also facilitate the emergence of quasi-particle states through a similar mechanism.…”

Shape coexistence close to $N=50$ in the neutron-rich isotope $^{80}$Ge investigated by IBM-2

“…In recent years, the advent of radioactive isotopes beams have been developed, which gives the access to exotic nuclei far from stability in both the neutron-deficient and neutronrich regimes [1,[6][7][8][9][10]. In the neutron-rich nuclei, the empirical evidence of shape coexistence has been observed along N = 20, N = 28 and the subshell gap N = 40, see Refs.…”