High-spin states and neutron-hole influence in ²⁰⁹At

Abstract

The properties of high-spin states in ²⁰⁹At have been studied with the ²⁰⁶Pb(⁶Li,3nγ)²⁰⁹At At reaction. In-beam measurements with Ge(Li) detectors of γ-ray excitation functions, γ-γ coincidences, γ-ray angular distributions, and pulsed beam-γ timing were made to establish decay schemes, level energies, spin-parity assignments, isomeric lifetimes, and magnetic moments. High-spin states involving three valence protons in the 1h_9/2, 2f_7/2, or 1i_13/2 orbitals were identified. The electromagnetic properties observed in ²⁰⁹At were compared with those in the closed-neutron core nucleus ²¹¹At to examine the influence of the two neutron holes on the proton structure; microscopic calculations of this influence were carried out in perturbation theory.