As it is well known, the single-nucleonic levels in a nucleus manifest either the Kramers degeneracy d=2, or, if a nucleus is spherical, a trivial ‘‘magnetic’’ degeneracy d=2j+1. It will be shown using the results of the realistic total nuclear energy calculations that a possibility of a fourfold degenerate levels exists in a number of N∼136 isotones due to their high intrinsic symmetry. Those exotic states are predicted to be isometric; they lie only a few hundreds of keV above the ground state. Other possible nuclear regions where the same mechanism may take place are indicated.

• Received 19 October 1993

DOI:https://doi.org/10.1103/PhysRevC.49.R1250