AR-31 AND S-27 - BETA-DELAYED 2-PROTON EMISSION AND MASS EXCESS

Beta-delayed two-proton decay is reported for the T(z) = -5/2 isotopes 31Ar and S-27 which were produced by fragmentation of Ar-36 at 85 MeV/u. The two-proton nature of this decay is established on the basis of the number of events which trigger two detectors or more in a silicon-detector telescope. The proton energy spectra give experimental values for the daughter energy levels and for the branching ratios. The deduced values of the 31Ar and S-27 masses are discussed and compared with mass predictions. For both nuclei, other channels like beta-3p and beta-p-alpha are to be searched for since the observed beta-2p and beta-p branches do not fully account for the total decay width of the isobaric analog states in the daughter nuclei. Partial decay schemes are proposed for 31Ar and S-27.