Level structures of 110,111,112,113Rh from measurements on 252Cf
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Level schemes of 111Rh and 113Rh are proposed from the analysis of -- coincidence data from a 252Cf spontaneous fission source with Gammasphere.These schemes have the highest excitation energies and spins yet established in these nuclei, as well as weakly populated bands not reported in earlier fission- work. From these data, information on shapes is inferred. By analogy with lighter Z=45 odd-even isotopes, tentative spins and parities are assigned to members of several rotational bands. In this region triaxial nuclear shapes are known to occur, and we carried out calculations for 111Rh and 113Rh with the triaxial-rotor-plus-particle model. The 7/2+g9/2 bands of both nuclei, as well as lighter isotopes studied by others, show similar signature splitting. Our model calculations give a reasonable fit to the signature splitting, collective sidebands, and transition probabilities at near-maximum triaxiality with 28. For the K=1/2+[431] band, experiment and model calculations do not fit well, which is accounted for by greater prolate deformation of the K= 1/2+ band, a case of shape coexistence. Our data on 110,112Rh show no backbending and thus support the idea of the band crossing in the ground band of the odd-A neighbors being due to alignment of an h11/2 neutron pair. In 111,113Rh above the band crossing (spins 21/2h) the ground band appears to split, with two similar branches. We consider the possibility that chiral doubling may be involved, but there are not enough levels to determine that.
