The projectile-target system Ca+ Ni has been used to produce the neutron deficient N = 50 isotones Tc, Ru, and Rh at high angular momentum. The multidetector array NORDBALL including particle selection was used. A large number of new levels were found in all three nuclei.Most of them can be interpreted as states with a neutron particle-hole excitation across the N = 50 shell gap, coupled to lower valence-proton configurations. Some of the observed levels above 11 MeV probably correspond to states with two neutrons excited across the shell gap.PACS number(s): 23.20.Lv, 25.70. Jj, 21.60.Cs, 27.60. +j

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The gamma -decay of excited states in the neutron-deficient nucleus 93Rh has been observed for the first time. The fusion-evaporation reaction 58Ni(40Ca,3p2n)93Rh at 187 MeV beam energy was used to produce 93Rh. The multidetector array NORDBALL including particle selection was used for identification. From gamma gamma -coincidence data a decay scheme of 23 transitions up to high angular momentum was constructed for 93Rh.

The present work presents, for the first time, the yrast level scheme of 91Ru. The level structure was investigated via the fusion-evaporation reaction 58Ni(40Ca, α2pn)91Ru at beam energies of 187 MeV using in-beam γ-ray spectroscopy techniques. The NORDBALL detector system including charged particle and neutron selection was used. The decay scheme was constructed on the basis of Compton suppressed γγ coincidences, intensity relations and measured γ-ray anisotropies. A number of positive as well as negative parity yrast levels was found with excitation energies up to 7.5 MeV and 9.6 MeV with maximum spin values of (41/2+) and at least 45/2− respectively. The experimental results are discussed in terms of shell-model configurations and the systematics of the structure of the vg9/2−3 configuration.

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