In-beam γ-ray spectroscopy of 211,213Ac and 211Ra

Abstract

The first in-beam 𝛾-ray spectroscopic study of the neutron-deficient actinium isotopes 211,213Ac has been carried out at the Accelerator Laboratory of the University of Jyväskylä using a highly selective recoil-decay tagging method with the jurogam 3 germanium-detector array and MARA separator. The nuclei of interest were produced using the 175Lu⁢(40Ar,4⁢𝑛)⁢211Ac and 180Hf⁢(37Cl,4⁢𝑛)⁢213Ac fusion-evaporation reactions. Excited states in 211Ac were observed for the first time. In 211Ac and 213Ac low-lying core-excited states whose excitation energies follow the systematic trends of their respective core states in even-even isotones 210Ra and 212Ra were identified. Additionally, we were able to extend the level scheme of 211Ra, which was also produced in the 40Ar+175Lu reaction. We also remeasured the half-lives of the ground states of these nuclei and also that of the (13/2+) isomeric state of 211Ra.