THE MASSES OF SE-70,SE-71

The masses of the neutron-deficient nuclei Se-70,Se-71 have been measu red using a direct time-of-flight technique following the fragmentatio n of a Kr-78 beam (73 MeV/nucleon). Mass excesses of -62.31 +/- 0.35(s yst.) +/- 0.30(stat.) and -63.49 +/- 0.25(syst.) +/- 0.20(stat.) MeV, respectively, were deduced, In addition, a novel technique based on st ripping was developed for the purification of heavy fragmentation beam s. This technique provides a good selectivity - typically isotopes of a single Z are transmitted - without altering the beam quality. (C) 19 98 Elsevier Science B.V.