Experimental beta-decay energies of short-lived light fission products

Abstract

The beta-decay energy of 20 nuclides in the mass region 88 _<A < 102 has been measured using the on-line mass separator LOHENGRIN. The experimental values obtained are compared with theoretical predictions of different mass formulae.

Nuclear structure effects in the mass region aroundA=100, derived from experimentalQ ? -values

“…The fl-endpoints obtained are given in Table 1; they agree very well with those measured in our earlier measurements [4,6]. With the decay scheme from [15[, a consistent Q~-value of 4575 + 30 keV (including a systematic error of 25 keV) is obtained, which agrees within errors with the value reported by Vogel et al [18].…”

ExperimentalQ ?-values of several short-lived nuclides with mass number 85?A?103

“…Its value is larger than 400 keV for all equations considered and has a maximum for the mass relation of Liran and Zeldes [20]. This is quite surprising, because in [2] this formula agreed much better with experiment than most of the others. This unexpected finding is due to a systematic discrepancy occuring for all mass equations after the main shell closure at N=50.…”

“…All predicted Qfvalues for ~~ are too high; the difference has its largest value for the mass relation of Liran and Zeldes. This discrepancy was already observed in [2] for the lighter odd-88 odd isotope 35Br53, it is an example of the inadequate treatment of nuclear shell effects found by Wing [1] for nuclei near stability. It is interesting to note that this systematic deviation is not present for the nuclei immediately following shell closure, i.e.…”

“…In all experiments, the LOHENGRIN mass-separator of the Institut von Laue-Langevin at Grenoble has been used. The preparation and counting of the sources and the handling of the data were done essentially in the same way as described in [2]. In addition to/37-coincidence measurements with the/~-detector telescope and the Ge(Li)-detector, for some The uncertainty in energy resulting from this calibration is about 50keV in the range between 2 and 9MeV and is included in the experimental errors given below for measured/3-endpoint energies.…”

Proton-neutron multiplets in96Y

“…Moreover, it has been shown recently [2] that the /~-decaying 10 s isomer of 96y is most probably the 8 + member of the (re g9/2, v gv/2) multiplet. The excitation energy of the isomer is not known, but the study [3] of the energies of the /3-particles of its decay show that it must lie around 1 MeV. Thus, every theoretical study of 96y has to explain the existence of this low-lying 8 + state and its long half-life.…”