Collectivity in the light xenon isotopes: A shell model study

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 Xe-108. 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 Sn-100 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 Xe-110,Xe-112 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 Xe-108,Xe-110 and examined the possible existence of isovector and isoscalar pairing condensates in these N similar to Z nuclei.