Beta decay energies and nuclear masses of148Ba,148La and151Pr

Abstract

Theβ-decay energy of the neutron-rich isotopes148Ba,148La and151Pr has been measured at the Institute Laue-Langevin (ILL). The148Ba- and148La-nuclei were produced using a high-temperature ion source at the OSTIS separator of this institute, whereas samples of151Pr were obtained from the thermal fission of239Pu, used as a target in the mass separator LOHENGRIN. At both instruments,βγ-coincidences were measured with a plastic scintillator telescope and a Ge(I)-detector, together withβ-singles andγ-singles spectra. Theβ-spectra emitted in coincidence with 44γ-lines in the decay of these nuclei have been evaluated. From their endpoint energies, the followingQβ-values have been obtained:Qβ(148Ba)=5115±60keV;Qβ(148La)=7255±55 keV;Qβ(151Pr)=4170±75 keV. Using these results, the nuclear massesA of these nuclei can be calculated with a relative error ΔA/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.