Abstract
Quadrupole moments of six high-spin isomers in the At isotopes have been measured with the level-mixing-spectroscopy method: (), (29/), (,), (39/,29/). The results show that level mixing spectroscopy is a promising technique to determine quadrupole moments of isomers that are difficult to measure by other in-beam hyperfine interaction methods. A large increase of the quadrupole moment is observed if neutrons are excited across or removed from the N=126 shell closure. This behavior is explained in terms of an enhanced core softness for fewer core neutrons; the aligned valence particles, moving in equatorial orbits, then easily polarize the core towards oblate deformation.
- Received 1 September 1989
DOI:https://doi.org/10.1103/PhysRevC.43.2566
©1991 American Physical Society