Beta decay properties ofSe67,68and the astrophysicalrp-process path

The [sup 67]Se and [sup 68]Se isotopes near the proton drip line were produced by spallation of zirconium with 600 MeV protons at CERN. Beta decay properties were determined for the first time using the selectivity of molecular ion beams at the on-line mass separator ISOLDE. Chemically selective production was obtained through separation of the molecular ion COSe[sup +]. The half-lives of [sup 67]Se and [sup 68]Se were measured as 107[plus minus]35 ms and 35.5[plus minus]0.7 s respectively. From [beta]-[gamma] and [gamma]-[gamma] coincidences, and conversion-electron measurements, a decay scheme was obtained for [sup 68]Se. For the [sup 68]As ground state and several excited states, spin and parity are unambiguously determined from [beta]-decay rates and electromagnetic multipolarity assignments. In addition to the strong Fermi branch between the mirror ground states of [sup 67]Se and [sup 67]As [[ital J][sup [pi]]=(5/2)[sup [minus]],[ital T][sub [ital z]]=[plus minus]1/2], a GT branch to an excited state in [sup 67]As is observed. Implications of [sup 67]Se and [sup 68]Se properties in the [ital rp]-process path are considered.