LIFETIME OF 26S AND A LIMIT FOR ITS 2p DECAY ENERGY.

The unknown isotope ²⁶S, expected to decay by two-proton (2p) emission, was studied theoretically and searched experimentally. The structure of this nucleus was examined within the relativistic mean field (RMF) approach. A method for taking into account the many-body structure in the three-body decay calculations was developed. The results of the RMF calculations were used as an input for the three-cluster decay model optimized for the study of a possible 2p decay branch of this nucleus. The experimental search for ²⁶S was performed by fragmentation of a 50.3 A MeV ³²S beam. No events of a particle-stable ²⁶S or ²⁵P (a presumably proton-unstable subsystem of ²⁶S) were observed. Based on the obtained production systematics, an upper half-life limit of T_1/2<79 ns was established from the time-of-flight through the fragment separator. Together with the theoretical lifetime estimates for two-proton decay, this gives a decay energy limit of Q_2p>640 keV for ²⁶S. Analogous limits for ²⁵P are found as T_1/2 < 38 ns and Q_p>110keV. In the case that the one-proton emission is the main branch of the ²⁶S decay, a limit Q_2p>230 keV would follow for this nucleus. According to these limits, it is likely that ²⁶S resides in the picosecond lifetime range. [ABSTRACT FROM AUTHOR]