Speaker
Description
j-1 anomaly remains a mystery [1] 60 years after the first observations that something is not quite right with the low-energy poitive-parity states in the odd-A medium-mass Ag nuclei. Within the Shell model, nuclei with three particles or holes on g9/2, should have 9/2+ as their lowest-lying state. Instead, these nuclei have 7/2+ at even lower energies, which is considered to be anomalous behaviour. Such ordering of the states of the πg9/2-3 multiplet can not be easily explained within the state-of-the-art theoretical models. Also, within the Shell model, the single-j occupation leads to forbidden M1 transitions between the multiplet members. Thus, E2 transition rates should dominate the Ag structure [2]. Hence, the electromagnetic transition rates can provide a stringent test to the purity of the wave functions. However, to obtain them experimentally we need lifetimes and mixing ratios data [3]. Unfortunately, such data are available only for very few nuclei of the 16 odd-A Ag nuclei, spanning the region between the 97Ag and 129Ag, which is not enough to track the structureral changes throughout the silver isotopic chain. Therefore, three years ago we started a campaign of plunger life-time measurements in the πg9/2-3 multiplet members. This research will be completed with Fast-timing data that we plan to take in future experiments at IFIN and elsewhere.
Bibliography
[1] S.Lalkovski, S.Kisyov, Evolution of the j-1 anomalous states of the j-3 multiplets, Phys.Rev.C106 (2022)064319
[2] S.Lalkovski, S.Kisyov, O.Yordanov, j-1 anomalous states and the electromagneti transition rates in the neutron mid-shell Ag nuclei, Acta Physica Polonica B55 (2024) A2
[3] S.Kisyov, S.Lalkovski, Structure of the odd-A Ag isotopes via algebraic approaches, Symmetry 17 (2025) 1276