High-spin states and collective oblate bands inNd139

Abstract

High spin states in 139 Nd nucleus have been reinvestigated with the reaction 128 Te ( 16 O, 5n) at a beam energy of 90 MeV. The level scheme has been expanded with spin up to 47/2h. At low spin, the yrast collective structure built on the νh −1 11/2 multiplet shows a triaxial shape with γ ≈ 32 • according to calculations of the triaxial rotor-plus-particle model. The configurations for some high spin states have been discussed from a systematic comparison with neighboring nuclei. Three collective oblate bands with γ ∼ −60 • at high spin were identified for the first time. A band crossing is observed aroundhω ∼ 0.4 MeV in one oblate band based on the 25/2 − level. The characteristics for these oblate bands have been discussed.

Identification of new transitions feeding the high-spin isomers in139Nd and140Nd nuclei

“…We do not discuss here all the observed states at low and medium spins, because many of them have been already observed and discussed in Refs. [15][16][17] for 139 Nd and in Refs. [2,8] for 140 Nd.…”

High-spin structures in the139Pr nucleus

“…Thus, at the high-spin states, the different quasiparticle configurations in a nucleus will give rise to different nuclear shapes. In previous publications, one of important results is the observation of oblate bands caused by such shape driving effects, for instance, in 131,136,137 La [2,12,13], 132 Ba [14], 137,138 Ce [15,16], 137,138 Pr [17,18], 139 Nd [19], and 140,141 Pm [20,21].…”

Energy levels in141Nd from fusion evaporation study

“…No heavy ion fusion evaporation reaction data were available in the literature. The neighbouring odd A-isotope 139 Nd [12,13] shows a triaxial shape at low spin, while at high spin two dipole bands, with positive and negative parity, have been observed. These bands were interpreted in the light of tilted axis cranking calculation as magnetic rotational bands [12].…”

“…The neighbouring odd A-isotope 139 Nd [12,13] shows a triaxial shape at low spin, while at high spin two dipole bands, with positive and negative parity, have been observed. These bands were interpreted in the light of tilted axis cranking calculation as magnetic rotational bands [12]. This work was initiated with the motivation to extend the high spin level scheme states of 141 Nd by the heavy ion fusion-evaporation reaction, and also to look for any possible occurrence of magnetic rotation in this nucleus.…”