Shell model high-spin states in 67 151 Ho84

Abstract

ABSTRACT:In an in-beam study of 6711084 we have established its high-spin states up to 10 MeV and have suggested spin assignments up to (49/2) at 6.2 MeV. The main decay-cascade proceeds through the yrast states of the ~h~i/~.vf~/2 and ~h~i/2vfz/~.hg/2 S-particle configurations, which are predicted with good accuracy in parameter-free shell-model calculations. States with one proton in d3/2, or involving vi13/2 or vf7/~• excitations were also identified.

Multiparticle configurations of excited states in Lu155

“…The increase in proton number would increase the proton occupancy of the h 11/2 state, increasing the probability of an interaction between an h 11/2 proton and an h 9/2 neutron. The inclusion of a strong [πh 11/2 , νh 9/2 ] 1 + interaction [2,3] provides a mechanism for the observed lowering of the 25/2 − state relative to the 27/2 − state with increasing Z. This interaction is forbidden in the 27/2 − state, as it is not possible for a spin of 27/2 to be constructed from the available angular momentum projections of the unpaired nucleons.…”

“…The (29/2 + ) and (31/2 + ) states are assumed to be a πh 11/2 ⊗ νf 7/2 i 13/2 configuration, as adopted for the N = 84 isotones 151 Ho and 153 Tm [2,3]. Higher-lying states could arise from the alignment of a pair of protons.…”

“…The relatively constant behaviour of the 27/2 − state contrasts with the lowering in excitation energy with increasing Z observed in other states that feature an h 9/2 neutron [1]. The similarities between the behaviour of the 27/2 − state and those built on the πh 11/2 ⊗νf 2 7/2 configuration have led to the proposal that a (πh 11/2 , νh 9/2 ) 1 + interaction, which is Pauli blocked in the 27/2 − state, is the dominant component lowering the states featuring an h 9/2 neutron [2].…”

“…Previous studies of isotones in this region have revealed that as the occupancy of the πh 11/2 orbital increases with increasing Z, states involving configurations with neutrons in the h 9/2 orbital are lowered in energy relative to those with neutrons in the f 7/2 orbital [1][2][3][4]. This observation has been attributed to an increasing attraction between h 11/2 protons and h 9/2 neutrons as the occu- * Present address: Department of Physics, University of Surrey, Guildford GU2 7XH, United Kingdom † Present address: Department of Physics, University of Guelph, Guelph, Ontario, N1G 2W1 Canada pancy of the h 11/2 proton orbital increases.…”

Evolution from quasivibrational to quasirotational structure in Tm155 and yrast 27/2− to

“…Excited states in the light rare-earth nuclei near A = 150 have exhibited a wealth of interesting physics, such as shape coexistence [1][2][3][4], structure evolution [5][6][7][8][9][10][11], and seniority inversion [12][13][14][15]. The properties of the low-lying states in these nuclei were found to be sensitive to small changes in neutron number N [16].…”