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The level structures of the N = 50 83As, 82Ge, and 81Ga isotones have been investigated by means of multi-nucleon transfer reactions. A first experiment was performed with the CLARA–PRISMA setup to identify these nuclei. A second experiment was carried out with the GASP array in order to deduce the γ-ray coincidence information. The results obtained on the high-spin states of such nuclei are used to test the stability of the N = 50 shell closure in the region of 78Ni ( Z = 28 ). The comparison of the experimental level schemes with the shell-model calculations yields an N = 50 energy gap value of 4.7(3) MeV at Z = 28 . This value, in a good agreement with the prediction of the finite-range liquid-drop model as well as with the recent large-scale shell model calculations, does not support a weakening of the N = 50 shell gap down to Z = 28 .

The lifetimes of five levels of the two-quasineutron band in 128 Ba populated via the 116 Cd( 16 O ,4 n) reaction were measured for the first time by means of the recoil-distance Doppler-shift method. For the data-analysis, a new version of the differential decay-curve method in singles-like mode was developed which takes into account the velocity distribution of the recoils and the effect of the Doppler-shift attenuation in the stopper. The high values of 〈K 2 〉 and K eff characterising the band are confirmed by the determined B (E2 ,I→I−2 ) and B (M1 ,I→I−1 ) transition strengths. At the same time, the rigid-rotor model is not able to describe the behaviour of the experimental B (E2 ,I→I−1 ) and B (M1 ,I→I−1 ) values. A new theoretical effort seems to be needed for a consistent explanation of the intraband transition strengths within two-quasiparticle bands in γ -soft nuclei.