On-line separation and identification of several short-lived fission products: Decay of 84Se, 91Kr, 97Y, 99Nb, 99Zr, 100, 101Nb and 101Zr

Abstract

A device for nuclear spectroscopy of short-lived fission products was run at the focus of the gas-filled on-line mass separator at the FRJ-2 reactor. By the known y-lines of long-lived fission products, a mass calibration of the separator was carried out. Several unknown shortlived fission products could be identified by investigating some very intense γ-lines. For these lines, the decay curves were measured, and β-γ coincidence spectra as well as γ-γ coincidence spectra were recorded. The data were assigned to eight nucleides for which the following half-lives, β-decay Q-values and γ-lines were determined: 84 Se T 1 2 = 3.5 min, Q β = 1.8 MeV, E γ = 406 keV, 91 Kr T 1 2 = 7.9 sec, Q β = 5.7 MeV, E γ = 111 and ≈ 630 keV, 97 Y T 1 2 = 1.11 sec, Q β = 5.7 MeV, E γ = 125 and 810 keV, 99 Nb T 1 2 = 14.3 sec, Q β = 3.7 MeV, E γ = 137 keV, 99 Zr T 1 2 = 2.4 sec, Q β = 4.5 MeV, E γ = 468, 548, 595 and ≈ 430 keV, 100 Nb T 1 2 = 6.6 sec, Q β = 6.5 MeV, E γ = 159 and 533 keV, 101 Nb T 1 2 = 7.0 sec, Q β = 4.6 MeV, E γ = 273 and 399 keV, 101 Zr T 1 2 = 3.3 sec, Q β = 6.5 MeV, E γ = 293 and ≈ 400 keV . In three of the eight cases, the decay curves permitted the following estimates for the half-lives of the precursors: 97 Sr, T 1 2 ≈ 0.4 sec; 99 Y, T 1 2 ≈ 0.8 sec and 100 Zr, T 1 2 ≈ 1.0 sec . For all these values, the corresponding errors are given in the main text. The results obtained in this investigation are compared, if possible, with published data from earlier β-decay or nuclear-reaction measurements; discrepancies are discussed. Using the new results and the published data, decay schemes are proposed for the eight nucleides.