Mass measurements of /sup 162/,/sup 163/Ta and nuclides in their. cap alpha. decay chains

Two weak ..cap alpha.. groups have been observed in /sup 127/I-induced reactions on /sup 40/Ca. The energies, apparent half-lives and excitation functions of these ..cap alpha.. groups have been measured. We confirm and make unambiguous a previous tentative assignment of these ..cap alpha.. groups to /sup 162/,/sup 163/Ta. Our assignment is based on their measured half-lives as well as on the good agreement between their excitation functions and those exhibited by well-known ..gamma.. rays from the decays of /sup 162/,/sup 163/Ta, identified in earlier studies with isotope-separated samples. The mass excesses of /sup 162/,/sup 163/Ta, as well as those of seven other nuclides in their ..cap alpha..-decay chains, have been deduced from the ..cap alpha..-decay data obtained in the present work and in previously published studies. The three heaviest members of the /sup 163/Ta chain are shown to have proton separation energies that are less than zero.