Spectroscopic studies of neutron-deficient light nuclei: decay properties of 21Mg, 25Si and 26P

Neutron‐deficient nuclei with Tz equals to −3/2 and −2 have been produced at the GANIL/LISE3 facility in fragmentation reactions of a 95 MeV/u 36Ar primary beam in a 12C target. For the first time, β‐delayed proton and β‐γ emission has been simultaneously observed in the decay of 21Mg, 25Si and 26P. The decay scheme of the latter is proposed and the Gamow‐Teller strength distribution in its β decay is compared to shell‐model calculations based on the USD interaction. The B(GT) values derived from the absolute measurement of the β‐branching ratios are in agreement with the quenching factor of about 60% obtained for allowed Gamow‐Teller transitions in this mass region. A precise half‐life of 43.7 (6) ms was determined for 26P, the β‐2p emission of which was studied. The expected contribution of spectroscopic studies of neutron‐rich nuclei is discussed with respect to the mirror asymmetry phenomenon occuring in analogous β decays.