Collectivity in the light xenon isotopes: A shell model study

Abstract

The lightest xenon isotopes are studied in the shell model framework, within a valence space that comprises all the orbits lying between the magic closures N = Z = 50 and N = Z = 82. The calculations produce collective deformed structures of triaxial nature that encompass nicely the known experimental data. Predictions are made for the (still unknown) N = Z nucleus 108 Xe. The results are interpreted in terms of the competition between the quadrupole correlations enhanced by the pseudo-SU(3) structure of the positive parity orbits and the pairing correlations brought in by the 0h 11/2 orbit. We also have studied the effect of the excitations from the 100 Sn core on our predictions. We show that the backbending in this region is due to the alignment of two particles in the 0h 11/2 orbit. In the N = Z case, one neutron and one proton align to J = 11 and T = 0. In 110,112 Xe the alignment begins in the J = 10, T = 1 channel and it is dominantly of neutron-neutron type. Approaching the band termination the alignment of a neutron-proton pair to J = 11 and T = 0 takes over. In a more academic mood, we have studied the role of the isovector and isoscalar pairing correlations on the structure on the yrast bands of 108,110 Xe and examined the possible existence of isovector and isoscalar pairing condensates in these N ∼ Z nuclei.

N=50core excited states studied in the4696Pd50nucleus

“…Studies in this region are stimulated by the existence of a variety of unresolved problems. First of all, nuclei approaching the N = Z line are believed to be candidates for a new type of (deuteron-like) pairing, but different theories disagree on this matter [1][2][3]. Second, the energies of the single-particle levels in 101 Sn are widely debated due to two contradictory experimental claims [4,5].…”

High-spin structure in the transitional nucleus Xe131 : Competitive neutron and proton alignment in the vicinity of the N=82 shell closure

“…The proton and neutron single-particle energies are based upon the energy levels in 133 Sb and 131 Sn. In addition, a calculation with the effective interaction GCN50:82 [86,87] was performed with the program KSHELL. Like the SN100PN interaction, the interaction is derived from a realistic G matrix based on the CD-Bonn potential.…”

16+Spin-Gap Isomer inCd96

“…The isovector (T ¼ 1) component of the interaction between like-nucleons is known to dominate in all non-self-conjugate nuclei while the T ¼ 1 np interaction has been shown to have a major influence on the N ¼ Z line below mass 80 due to the large overlap of the proton and neutron wave functions [16]. Although calculations suggest an important influence of the isoscalar (T ¼ 0) np interaction on the structure of medium-heavy N ¼ Z nuclei, its role has been less clear and often debated [17][18][19][20]. Very recent experimental work has claimed the first indications for the crucial role of this interaction at low spins in 92 Pd, that are supported by shell-model (SM) calculations [2].…”