Shape coexistence in the light Po isotopes

Abstract

The systematics of the even light P o isotopes (N126) are studied in the framework of the Particle-Core Model. The strong perturbation of the systematics in the very light isotopes is interpreted as arising from the interaction between regular and intruder structures. Results of Potential Energy Surface (PES) calculations and predictions of the Pairing Vibration Model support this interpretation. The mixing between the regular and intruder structures is studied within the IBM-2 and in a simple two-state mixing picture. Matrix elements of the interaction and their spin-dependence are extracted. The 'reconstructed systematics' show the coexistence of a spherical structure, which v aries little with the neutron number, with an intruder band, strongly lowered in energy as the neutron numberapproaches midshell. The crossing of the two congurations takes place over a few isotopes; the intruder band becomes the ground-state conguration in 192 Po.

Lifetimes of intruder states in 186Pb, 188Pb and 194Po

“…For 192 Po and 194 Po, configuration mixing calculations have been carried out using the energy level systematics [15]. All these studies indicate an increasing contribution of the deformed structure in the ground state when approaching 192 Po, which is also supported by the results obtained with several theoretical models [26].…”

Platinum nuclei: Concealed configuration mixing and shape coexistence

“…When carefully inspecting the changing structure and systematics in the Po nuclei (which have two protons outside the Pb core), the observed spectra do not display an obvious presence of extra intruder bands. However, recent studies point strongly towards the presence of intruding 2p-2h excitations (or the presence of an oblate and a spherical band in mean-field terminology) near A = 192 [7,14,16,19,[78][79][80].…”

Nuclear shape coexistence in Po isotopes: An interacting boson model study

“…Energy surface calculations, covering the β-γ plane were carried out using a deformed Woods-Saxon potential, resulting in the presence of three minima in the mass region A = 190 to A = 186 [124]. The above results were confirmed later by Smirnova et al [126], this time using a self-consistent Hartree-Fock-Bogoliubov approach using the SLy4 Skyrme force [26], indicating rather wide minima in A = 196-194, a lowest oblate minimum at A = 192 and A = 190, and a turning into prolate at A = 188.…”