Elsevier

Nuclear Physics A

Volume 246, Issue 2, 21 July 1975, Pages 425-444
Nuclear Physics A

Beta-decay properties of strongly neutron-rich nuclei

https://doi.org/10.1016/0375-9474(75)90657-0Get rights and content

Abstract

Experimental β-strength functions for about 50 neutron-rich mass-separated fission products with half-lives between 0.8 s and 30 s have been obtained at the OSIRIS facility. The β-strength to excited states depopulating by delayed-neutron emission is evaluated separately. The β strength functions are found to increase strongly with excitation energy, which is in contrast to the approximately energy-independent β-strength found for EC decay. By using semiempirical values for the level density, the average transition rate per energy level was evaluated under the assumption that only allowed transitions contribute to the decay. This alternative way of analyzing the data gives a more uniform picture of the β-decay to highly excited states since the transition rates are found to be roughly independent of excitation energy (above the pairing energy). A model of constant transition rate to each final level is introduced and its systematic behaviour is studied. Its use for estimating half-lives of unmeasured nuclides is of value for calculations on nucleosynthesis by the “r-process”. (A listing of β-feed and β-strength functions is available on request.)

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    This work was financially supported by the Swedish Atomic Research Council.

    Present address: The Swedish Research Council's Laboratory, Studsvik, Nyköping, Sweden.

    1

    It is a great pleasure to acknowledge valuable discussions with Profs. G. Andersson, P.G. Hansen and Drs. B. Jonson and K. Takahashi. For excellent isotope separator performance L. Jacobsson and O.C. Jonson are gratefully acknowledged. The authors are indebted to Dr. K. Bonde Nielsen for kindly providing the plastic detector.

    ††

    Present address: Gessellschaft für Schwerionenforschung mbH., Darmstadt, Federal Republic of Germany.

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