Change in structure between the =1/2 states in Tl and Au

Cubiss, J. G.*; Barzakh, A. E.*; Andreyev, A. N.; 他57名*

Physics Letters B, 786, p.355 - 363, 2018/11

https://doi.org/10.1016/j.physletb.2018.10.005

The first accurate measurements of the -decay branching ratio and half-life of the I=1/2 ground state in Tl have been made, along with the first determination of the magnetic moments and I=1/2 spin assignments of the ground states in Au. The results are discussed within the complementary systematics of the reduced -decay widths and nuclear g factors of low-lying, I=1/2states in the neutron-deficient lead region. The findings shed light on the unexpected hindrance of the 1/2 1/2, Tl Au decay, which is explained by a mixing of 3sand 2d configurations in Au, whilst Tl remains a near-pure 3s. This conclusion is inferred from the g factor of Au which has an intermediate value between those of 3s and 2d states. A similar mixed configuration is proposed for the I=1/2 ground state of Au. This mixing may provide evidence for triaxial shapes in the ground states in these nuclei.