High-Spin Isomers in N=83 Isotones

High-spin isomers in N=83 isotones have been systematically studied. Spin-parities of these isomers are 49/2⁺ and 27⁺ for odd and odd-odd nuclei, respectively. These isomers are of stretch coupled configurations and have oblate shapes.

Experimental results were compared with those calculated by a deformed independent particle model(DIPM). Excitation energies of high-spin isomers in N=83 isotones with 60≦Z≦66 are almost constant. This constancy can be attributed to a decrease of the shell gap energy of Z=64 from 2.4 to 1.9MeV, as a proton number decreases from Z=64 to 60. These isomers are considered to be shape isomers, as the results of the DIPM calculation indicates that high-spin isomers may be caused by the sudden shape change from a near spherical to an oblate shape.

Search for high-spin isomers with the same isomerism has been experimentally started in N=51 isotones.