Reinvestigation of the Direct Two-Proton Decay of the Long-Lived IsomerAgm94[0.4 s, 6.7 MeV, (21+)]

Abstract

An attempt to confirm the reported direct one-proton and two-proton decays of the (21+) isomer at 6.7(5) MeV in 94 Ag has been made. The 0.39(4) s half-life of the isomer permitted use of a helium-jet system to transport reaction products from the 40 Ca + nat Ni reaction at 197 MeV to a low-background area; 24 gas ∆E-(Si) E detector telescopes were used to identify emitted protons down to 0.4 MeV. No evidence was obtained for two-proton radioactivity with a summed energy of 1.9(1) MeV and a branching ratio of 0.5(3)%. Two groups of one-proton radioactivity from this isomer had also been reported; our data confirm the lower energy group at 0.79(3) MeV with its branching ratio of 1.9(5)%.

Observation of a new high-spin isomer inPd94

“…One of the most striking cases is the (21 + ) level in 94 Ag, with recent papers reporting evidence for a variety of particle decay channels: β [7,8], βp [9], p [10], and 2p [11]. The latter of these is the subject of much debate in the literature [12][13][14][15][16].…”

“…One of the most striking cases is the (21 + ) level in 94 Ag, with recent papers reporting evidence for a variety of particle decay channels: β [7,8], βp [9], p [10], and 2p [11]. The latter of these is the subject of much debate in the literature [12][13][14][15][16].The T z = 1 nuclide 94 Pd has been studied in a number of experiments [7,8,[17][18][19][20][21] and has a known 14 + isomer that decays through γ decay and internal conversion (IC). The half-life of this state has been measured previously, yielding values of 800 (200) [7,8].…”

Blurring the Boundaries: Decays of Multiparticle Isomers at the Proton Drip Line

“…This formula is based on the systematics of proton-decay half-lives, after taking into account the effects of the Coulomb barrier, Δl, and the Q p value. Although the direct proton decay of the 19 − isomer in 158 Ta to the 7=2 − state in 157 Hf would have a much longer partial half-life than the decays of low-lying states, the most favoured proton-decay branches to excited states in 157 Hf would be faster, which is a similar situation to that observed in 94 Ag [25,26]. However, the proton decays would not compete with the measured γ-and α-decay branches, as is observed experimentally.…”

“…This remains the highest known Δl value for any proton decay [2]. More recently, direct proton emission has been observed from a (21 þ ) isomer in 94 47 Ag [25,26]. This 6.7 MeV isomer decays to at least one excited state in 93 Pd with a branching ratio of a few percent.…”

Untitled

“…-In a helium-jet experiment without mass separation, one of the oneproton line of 94m Ag was confirmed whereas the two-proton radioactivity was not observed [17].…”