Limits of observable proton-emitting nuclei between theN=82andZ=82shell closures

Abstract

The regular systematic behavior of Q p values is analyzed to provide a basis for estimating Q values for as yet unknown proton and α decays. These estimates are used in predicting partial half-lives for proton and α-particle emission from states in Ta, Re, Ir, and Au nuclei beyond the proton drip line. The implications of these predictions for further experimental study in this region are discussed.

αdecay of theπh11/2isomer inIr164Drummond1, O’Donnell2, Page3 et al. 2014Phys. Rev. CSelf Cite14010View full textAdd to dashboardCite

“…Both of these Q values are consistent with those estimated in Ref. [9], where partial half-lives of ∼10 ms and ∼1 ms were predicted for proton emission and α-particle emission, respectively. Neither of these decay modes is therefore able to compete effectively with the observed γ -decay branch from this 2.8 μs isomer.…”

“…The α-decay branch of the πh 11/2 isomeric state in 164 Ir has been identified, establishing the excitation energy of the corresponding state in the daughter nuclide, 160 Re. The results agree well with values estimated from local extrapolations of the systematics of proton-decay Q values [9]. Corresponding estimates for the even-lighter isotopes 162,163 Ir suggest that half-lives of 90 ns and 410 ns, respectively, could be expected [9], which may be too short for study using recoil separator devices such as that used in the present work.…”

“…The γ -ray cascade identified from the decay of this πh 11/2 isomer comprises a 96 keV E2 transition followed by a 38 keV E1 transition. However, other unobserved transitions might be expected to form part of this cascade since the excitation energy of the isomer has been estimated from systematics to be 185 ± 21 keV [9]. By using this estimate, partial half-lives for proton and α-particle emission can be predicted, and these values are significantly longer than that observed from the γ decay of the state.…”

“…1). The Q value for this α decay has been estimated from systematics [9], from which a branching ratio of ∼8% could be expected. Such a low α-decay branch would have been below the sensitivity limits of the previous studies of 164 Ir, in which proton-decay yields of only ∼five events [2] and ∼eight events [5] were obtained.…”

Recent developments in radioactive charged-particle emissions and related phenomena

“…The results are astonishingly good. For instance in the heavy isotopes of T a, Re, Ir and Au the root-mean-square deviation is of 34 keV from the extrapolated estimates to the corresponding known values [33]. With the Q-values thus obtained one evaluates the half lives by using the WKB approximation.…”