beta-delayed neutron decay of Y-104, Tc-112, Tc-113 and Tc-114: test of half-life predictions for neutron-rich isotopes of refractory elements

Beta-decay gross properties of neutron-rich isotopes Y-104 and Tc-112,Tc-11 3,Tc-114 produced in 25 MeV proton-induced fission of U-238 have been measu red. Decays of Y-104 With a half-life of 180 +/- 60 ms and of Tc-114 With a half-life of 150 +/- 30 ms are reported for the first time. Beta-delayed n eutron emission probabilities of Tc-112,Tc-113,Tc-114 are determined as (1. 5 +/- 0.2)%, (2.1 +/- 0.3)% and (1.3 +/- 0.4)%, respectively. Comparison of the observed P-n values with a recent theoretical calculation based on def ormed quasiparticle random phase approximation (QRPA) shows good overall ag reement for Tc isotopes. However, comparison of beta-decay half-lives of ne utron-rich isotopes of Y to Rh with the QRPA model and the refined gross th eory shows only modest agreement, pointing to inadequate treatment of struc ture of these very neutron-rich nuclei lying in a region of rapidly changin g deformation. (C) 1999 Elsevier Science B.V. All rights reserved.