Structure studies on the nuclides 96Zr and 98Zr via the high-spin β--decays of the Y fission products

In the framework of this thesis the β--decay of the high-spin states of the 96Y and 98Y parent nuclei of 96Zr and 98Zr was studied. These isomeric states were populated in the fission of the 235U by means of thermal reactor neutrons. The term schemes of 96Zr and 98Zr could be essentially extended. By the evaluation of the angular correlations in 96Zr for ten levels precise spin assignments could be made and for seven states the possible spin values confined to few alternatives. The study of the β--feeding resulted that mainly the 4390 keV level in 96Zr is populated by the β--decay with a logft value of 5.0. The angular-correlation analysis gives a spin I = 8 for the 4390 keV level. With this experimental results and theoretical calculations with the IBFFM model on spin and parity I-π = 8+ of the 96Y high-spin isomer with a [πg9/2xμg7/2] configuration could be concluded. Furthermore the mixing parameters δ for two mixed M1/E2 transitions were determined which suggest with the values δ289 = -0.5(4) for the (62+ → 61+) and δ475 = 0.1(2) for the (42+ → 41+) transitions predominating M1 multipolarities. In 98Zr only the angular correlation of the cascade of the four most intensive transitions 1223, 620, 647, and 1801 keV was studied whereby also here the spins of each level could be determined. It resulted that both an I = 6 state at an energy of E = 4292 keV and an I = 4 level at E = 2491 keV in 98Zr is strongly populated by the β--decay. Therefore it is assumed that spin and parity o the β--decaying high-spin isomer of 98Y Iπ = 5+ are which shall be confirmed by theoretical calculations with the IBFFM model. (orig./HSI)