High-spin states in the odd-odd nucleusAt212

Abstract

The properties of high-spin states in $^{212}\mathrm{At}$, including three isomers, have been studied with the $^{208}\mathrm{Pb}$($^{7}\mathrm{Li}$,$3n$)$^{212}\mathrm{At}$ reaction. In-beam measurements with Ge(Li) and intrinsic Ge detectors of $\ensuremath{\gamma}$-ray excitation functions, $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coincidences, $\ensuremath{\gamma}$-ray angular distributions, pulsed-beam-$\ensuremath{\gamma}$ timing, and perturbed angular distributions with an applied magnetic field were made to establish a decay scheme, level energies, $\ensuremath{\gamma}$-ray multipolarities, spin-parity assignments, isomeric lifetimes, and $g$ factors. High-spin states up to $15\ensuremath{\hbar}$ were identified as predominantly three proton [${(\ensuremath{\pi}{h}_{\frac{9}{2}})}^{3}$ or ${(\ensuremath{\pi}{h}_{\frac{9}{2}})}^{2}$ ($\ensuremath{\pi}{i}_{\frac{13}{2}}$)] states of the ($N=126$) $^{211}\mathrm{At}$ nucleus coupled to a neutron in either the ${g}_{\frac{9}{2}}$, ${i}_{\frac{11}{2}}$, or ${j}_{\frac{15}{2}}$ orbitals. The experimental energy levels, $g$ factors, and $B(M2)$ value are compared with shell model calculations.NUCLEAR REACTIONS $^{208}\mathrm{Pb}$($^{7}\mathrm{Li}$,$3n$)$^{212}\mathrm{At}$ $E=32\ensuremath{-}44$ MeV; measured $\ensuremath{\gamma}$ excitations, $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coin, $\ensuremath{\gamma}\ensuremath{-}W(\ensuremath{\theta})$, pulsed-beam-$\ensuremath{\gamma}$ timing, perturbed angular distributions; deduced levels, $\ensuremath{\gamma}$ multipolarities, ${J}^{\ensuremath{\pi}}$, ${T}_{\frac{1}{2}}$, $B(E1)$, $B(M2)$, $g$.