The decays of the [formula omitted] β-delayed proton precursors 83Zr, 87Mo and 91mRu

Abstract

The decays of the nuclides 83Zr, 87Mo and 91mRu have been studied with singles proton counting as well as with pX and pγ coincidences. The half-lives for the three nuclides were measured to be 37.8 ± 1.1 s, 13.3 ± 0.4 s and 7.6 ± 0.8 s, respectively. The proton branch in the decay of 83Zr that populates the first excited state in 82Sr was measured to be (6 ± 4) % of the total delayed proton decay. The corresponding branch in the decay of 87Mo, populating the first excited state in 86Zr was measured to be (15 ± 8) %. Restrictions to the possible spin and parity assignments of 83Zr and 87Mo were deduced from comparisons between the experimental excited-state branches, and those predicted from a statistical model of delayed particle decay. Fits to the endpoints of the delayed proton spectra from 83Zr and 87Mo yielded values of the energy available for delayed proton decay ( Q e.c.− B p) of 2.75 ± 0.10 MeV and 3.7 ± 0.3 MeV, respectively. Comparison between calculated and experimental proton spectra was used as an argument that the source of 91Ru activity is actually a 1 2 − isomer.