Reinvestigation of direct two-proton radioactivity of $^{94}$Ag$^{m }$(J$^{\pi }$= 21$^{+}$, 6.7 MeV)

Both direct one-proton decay and direct two-proton decay of $^{94}$Ag$^{m}$ from this long-lived (0.4 s) isomeric state have been reported by Mukha et al. in experiments performed with the GSI on-line mass separator [1]. In the former decay, two proton groups with energies of 0.79 and 1.01 MeV were observed, each having a branching ratio of about 2{\%}; in the latter decay, coincident events with a threshold energy of 0.4 MeV and a summed decay energy of 1.9 MeV were observed in coincidence with $\gamma $-decays in the $^{92}$Rh daughter and were assigned to be coincident protons with a branching ratio of 0.5(3){\%}. We have recently utilized our helium-jet system at the Berkeley 88-inch cyclotron to repeat this experiment, again employing the $^{58}$Ni($^{40}$Ca,p3n) reaction at 192 MeV. Reaction products were transported via a capillary to a detection area and collected on a slowly rotating wheel in front of an assembly of 24 $\Delta $E$_{gas}-\Delta $E$_{gas}$ - E$_{Si}$ detector telescopes with a threshold of 0.4 MeV for identifying protons. The beta-particle background is reduced enough in several of these telescopes to clearly observe the 0.79 MeV single proton decay from $^{94}$Ag$^{m}$. Data analysis is continuing and results of the search for coincident, identified protons will be presented. [1] Mukha et al., Nature \underline {439}, 298 (2006) and references therein.