Anomalousα-decay rate ofPb192

Abstract

An anomalous behavior has been reported by Hansen et al. for the $\ensuremath{\alpha}$-decay rates of neutron-deficient lead isotopes. In particular, the $\ensuremath{\alpha}$ reduced width of $^{192}\mathrm{Pb}$ appears to be large. Their $\ensuremath{\alpha}$-branching ratios, however, are based on (electron capture + ${\ensuremath{\beta}}^{+}$) decay strengths deduced from $K$ x-ray intensities. More precise values can be obtained if the (electron capture + ${\ensuremath{\beta}}^{+}$) decay scheme is known. To this end we investigated the decay properties of $^{192}\mathrm{Pb}$ with the use of an on-line isotope separator. The nuclide was produced in the $^{180}\mathrm{W}$($^{16}\mathrm{O}$,$4n$) reaction. Singles and coincidence $\ensuremath{\gamma}$-ray data as well as singles conversion-electron spectra were accumulated. Also, singles $\ensuremath{\gamma}$-ray, x-ray, and $\ensuremath{\alpha}$-particle spectra were taken with the three detectors placed in calibrated geometries. The $^{192}\mathrm{Pb}$ $\ensuremath{\alpha}$ reduced width was found to be lower by a factor of 2 from that of Hansen et al. but nevertheless much larger than one would expect from neighboring $\ensuremath{\alpha}$-emitting nuclides.RADIOACTIVITY $^{192}\mathrm{Pb}$ measured ${T}_{\frac{1}{2}}$, ${E}_{\ensuremath{\gamma}}$, ${I}_{\ensuremath{\gamma}}$, ${I}_{\mathrm{ce}}$, ${E}_{\ensuremath{\alpha}}$, ${I}_{\ensuremath{\alpha}}$, $\ensuremath{\gamma}\ensuremath{\gamma}$ coin; $^{192}\mathrm{Tl}$ deduced levels; $^{192}\mathrm{Pb}$ deduced $\ensuremath{\alpha}$-decay reduced width. Mass separation.