Excited states and signature inversion inCs116

Abstract

Excited states have been observed for the first time in the very neutron-deficient, odd-odd nucleus, 116 55 Cs 61 . The assignment to 116 Cs has been made by the detection of γ rays in coincidence with evaporated charged particles and with evaporation residues. The observed states form a rotational band which has been assigned to the ν(h 11/2 ) ⊗ π (h 11/2 ) configuration. Tentative spin assignments have been made on the basis of systematic comparisons with neighboring cesium isotopes. A low-spin signature inversion is observed in the band at a rotational frequency of about 0.23 MeV/h. The observed signature inversions in the odd-odd 116−126 Cs isotopes have been compared with the results of extended total Routhian surface calculations, in which signature inversion arises as a consequence of quadrupole-pairing correlations and triaxial deformation. As previously shown for some of the odd-odd A 120 isotopes, the calculations reproduce the signature inversions reasonably well.

γ-ray spectroscopy of the odd-oddN=Z+2deformed proton emitter112Cs

“…The data for 114−126 Cs are taken from Refs. [3,17,21,22,[37][38][39][40][41] with spin assignments from Ref. [42].…”

“…In the neighboring heavier odd-odd cesium isotopes 114,116,118 Cs, decay from the lowest observed state in the most intense rotational band to the ground state is not observed. This is presumably due to the low detection efficiency for low-energy transitions with the apparatus used [20][21][22]. In 120 Cs, decay of the 10 + yrast band-head proceeds to the ground state by multiple low-energy, low-intensity transitions which were observed through the use of low-energy photon (LEPS) detectors [18].…”

“…Thus, in odd-odd 118,120 Cs (N = 63, 65), multiple high-spin two-quasiparticle rotational bands have been identified [3,[17][18][19][20]. For 116 Cs (N = 61), just one rotational band has been observed, assumed to be built on the yrast ν(h 11/2 ) ⊗ π(h 11/2 ) configuration [21]. Recently, in 114 Cs (N = 59), a sequence of around six gamma-ray transitions has been identified, which is assigned to form the favored-signature sequence of the yrast ν(h 11/2 ) ⊗ π(h 11/2 ) configuration [22].…”

Complete set of proton excitations in Cs119

“…The recent spectroscopic studies of cesium nuclei have been focused on chirality, which was observed in a long sequence of odd-odd nuclei from 122 Cs to 132 Cs [1]. The odd-even Cs nuclei have been the object of investigations devoted to the evolution of the collective properties far from stability [2][3][4][5][6][7][8][9][10][11][12]. However, the study of the lightest Cs nuclei is confronted with the increasing difficulty to populate high-spin states using fusion-evaporation reactions, due to the limited choice of projectile-target combinations and the small cross sections for neutron evaporation close to the proton drip-line.…”

Rich band structure and multiple long-lived isomers in the odd-odd Cs118 nucleus

“…The lightest odd-odd nucleus in the Cs chain with a known rich band structure is 120 Cs, in which five band structures have been observed [3,4]. In the lighter 112,114,116,118 Cs nuclei only one rotational structure has been identified, built on the π h 11/2 ⊗ νh 11/2 configuration [5][6][7][8]. The lightest odd-odd Cs nucleus with known spectroscopic information is the proton emitter 112 Cs [9,10], in which five firm and two tentative transitions have been identified and assigned to the π h 11/2 ⊗ νh 11/2 configuration based on systematics [5].…”