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The endpoint energies of r in 15 neuron-rich nuclei with mass numbers 101

The beta-decay energy of 20 nuclides in the mass region 88 _

The fl-decay energy of the neutron-rich isotopes 148Ba, 14SLa and ~5~pr has been measured at the Institute Laue-Langevin (ILL). The t4aBa-and ~48La-nuclei were produced using a high-temperature ion source at the OSTIS separator of this institute, whereas samples of ~51pr were obtained from the thermal fission of 239pu, used as a target in the mass separator LOHENGRIN. At both instruments, fiT-coincidences were measured with a plastic scintillator telescope and a Ge(I)-detector, together with//-singles and 7-singles spectra. The//-spectra emitted in coincidence with 44~)-lines in the decay of these nuclei have been evaluated. From their endpoint energies, the following Qa-values have been obtained: Qa(lgSBa) = 5115_ 60 keV; Qp(14SLa) = 7255_ 55 keV; Qp(~5 tPr)= 4170 +_ 75 keV. Using these results, the nuclear masses A of these nuclei can be calculated with a relative error AA/A~-5.10 -7. In addition, the two-neutron separation energies and the mass excesses have been derived; the results are compared with recent predictions of theoretical mass calculations.

The /?-endpoint energies of very neutron-rich Rb and Cs isotopes with mass numbers 94_< A < 98 and 142_ A_< 146, respectively, have been measured with a plastic scintillator/?-telescope at the on-line mass separator OSTIS. From these, Q~-values and mass excesses are calculated and compared with the results obtained in direct mass determinations.