Speaker
Description
Since December 2020 a series of four experiments has been conducted to probe systematically the structure of all odd-A neutron-deficient actinium isotopes from $^{207}$Ac to $^{213}$Ac. In this campaign both recoil separators, RITU and MARA, of the Accelerator Laboratory of University of Jyväskylä, Finland (JYFL-ACCLAB) were employed. These experiments used fusion-evaporation reactions to produce the nuclei of interest, and the events associated with actinium isotopes were identified through very selective recoil-decay tagging method (RDT). In this talk a brief introduction will be provided to the RDT studies at JYFL-ACCLAB, followed by a discussion on the results of this campaign, some of which has been recently published [1], and some will be published in near future [2]. The main outcome of these experiments is that the structure of the studied actinium nuclei resembles strongly that of the underlying even-even radium core of a given isotope. The odd h$_{9/2}$ proton of actinium ground states appear to systematically act as a “passive spectator” and it contributes very little to the lowest exited states. Similar effect has been observed previously in nearby francium and astatine nuclei, see, for example Refs. [3-4] and references therein.
[1] J. Louko et al., Phys. Rev. C 110 (2024) 034311.
[2] H. Kokkonen et al., Under review in Phys. Rev. C
[3] U. Jakobsson et al., Phys. Rev. C 87 (2013) 054320.
[4] K. Auranen et al., Phys. Rev. C 91 (2015) 024324.