Beta-decay half-lives and neutron-emission probabilities of very neutron-rich Y to Tc isotopes

Neutron-rich Y-39 to Tc-43 isotopes have been produced by fission of uranium with a 50 MeV H-2(+) beam, Beta-decay half-lives, delayed neutron-emission probabilities, and production yields have been measured and compared with theory. Beta decay of 4 new isotopes is reported, and the beta-delayed neutron-emission mode has been discovered for 12 isotopes of the elements niobium and technetium. The results compared to quasiparticle random phase approximation predictions indicate the increasing importance of fast beta transitions to high-lying states of nuclei with large neutron excess.