Puzzle on isomeric configurations in and around N=126 closed shell

The puzzle of finding consistent nuclear configurations to explain both the decay probabilities and moments of the 9/2(-), 8(+), and 21/2(-) isomers in and around the N = 126 closed shell has been approached in the generalized seniority scheme. Though h(9/2) is the dominant orbital near Fermi energy, the role of configuration mixing from the surrounding f(7/2) and i(13/2) orbitals is found to be very important for the consistent explanation of all the isomeric properties such as the B(E2) rates, Q moments, and g factors. The structural behavior of the closed shell N = 126 isotonic isomers turns out to be very similar to that of the N = 124 and N = 128 isotonic isomers, which have two neutron holes and two neutron particles, respectively. This is due to the pairing symmetries of nuclear many-body Hamiltonian. As confirmation, the microscopic shell model occupancies are also calculated for these isomers in the N = 126 chain which support the generalized seniority results. Additional arguments using the systematics of odd-proton 9/2(-) states in T1 (Z = 81), Bi (Z = 83), At (Z = 85), and Fr (Z = 87) isotopes are also presented.

Automated summary

The puzzle of finding consistent nuclear configurations for explaining the properties of isomers around the N = 126 closed shell has been solved using the generalized seniority scheme. The dominant orbital near Fermi energy is found to be h(9/2), but the mixing of configurations from surrounding f(7/2) and i(13/2) orbitals is crucial for explaining the properties of all isomers. The structural behavior of N = 126 isotonic isomers is similar to that of N = 124 and N = 128 isotonic isomers, due to the pairing symmetries of the nuclear many-body Hamiltonian.