In-beam study of high-spin states in199,200,201Po and systematical features of Z=84 polonium isotopes

Excited states in^199,200,201Po were populated in the reactions¹²C+¹⁹⁴Pt and¹²C+¹⁹⁵Pt. The subsequentγ-radiation was studied using conventional in-beam spectroscopic methods. States with spins up to (29/2), 18 and ≧35/2?, respectively, were populated in the three nuclides. Three isomeric states with the following half-lives were observed in²⁰⁰Po:T _1/2(8⁺)=90(15) ns,T _1/2(11^?)=120(20) ns andT _1/2(12⁺)=267(4) ns. The structure of the excited states was interpreted within the framework of the spherical shell model. The three isomers are suggested to be two-quasiparticle states with configurationsπ(h _{2 2})_8J, π(h₉i_13/2)₁₁- and v(i _{1 3/2 ?2})₁₂₊. A self-consistent Hartree-Fock calculation was performed to obtain ground-state deformations of the neighbouring Pb cores. From the results of the experiments and the calculations it was concluded that no appreciable deformations of the cores are manifested in the yrast states of these three Po nuclei.