Medium-spin γ-ray spectroscopy of the transitional nucleusEr160

Abstract

The nucleus 160 Er, with the structural parameter R 4/2 = E(4 + 1)/E(2 + 1) = 3.10, falls on the transition path between the critical point of the vibrator-rotor shape phase transition and the rigid rotor limit, thus serving as a critical test of the CBS rotor model, which describes this transition region. Medium-spin states of 160 Er have been populated via the reaction 159 Tb(6 Li,5n) and new levels have been identified and interpreted as the even-spin members of the γ band and members of the β vibrational band. Level energies and branching ratios are compared to the CBS rotor model predictions.

Investigation of excited 0+ states in 160Er populated via the (p, t) two-neutron transfer reaction

“…Members up to J π = 4 + were assigned by comparison of angular distributions to DWBA calculations. It is worth noting that some of the members of the higher-lying K π = 0 + and K π = 2 + bands are speculative, motivated by the similarity of the 160 Er band structures to those of 162 Er and 152 Sm, but are in agreement with those observed in unevaluated works [10,25].…”

Collectivity of0+states inGd160

“…Theoretical efforts [14][15][16][17][18][19][20][21][22] abound and continue to offer possible interpretations of these low-lying excitations in deformed nuclei.…”

“…Another recent development describes nuclei at or near the onset of deformation within the Bohr Hamiltonian in the limit of rigid prolate axial symmetry with confined β-soft potentials [16,17,19]. These studies and others [32][33][34] on the nature of K π = 0 + bands in deformed nuclei show widely varying levels of collectivity for the first excited 0 + states.…”

Structure changes inEr160from low to ultrahigh spin

“…5(a) and (b). A total of fifteen new in-band transitions and three new linking transitions were observed extending the band from the previously known (13 + ) state [21,22] up to a possible (43 + ) state. The 907, 970 and 1020 keV γ rays connect this band to the yrast band and are labeled with triangles in Fig.…”

“…Previous work has exposed a wide variety of rotational and vibrational bands [21][22][23] in this nucleus and its yrast structure has been observed up to ∼ 50h [24,25]. The present article reports on the observation of new rotational bands and extensions to existing structures and discusses these in the framework of the cranked shell model.…”