Shapes of ${}^{192,190}\mathrm{Pb}$ ground states from $\beta$-decay studies using the total-absorption technique

The $\beta$ decay of ${}^{192,190}\mathrm{Pb}$ has been studied using the total absorption technique at the ISOLDE (CERN) facility. The $\beta$-decay strength deduced from the measurements, combined with QRPA theoretical calculations, allow us to infer that the ground states of the ${}^{192,190}\mathrm{Pb}$ isotopes are spherical. These results represent the first application of the shape determination method using the total absorption technique for heavy nuclei and in a region where there is considerable interest in nuclear shapes and shape effects.

Figure 1

X-ray gates used for the generation of the analysed spectrum for ${}^{192}\mathrm{Pb}$ decay. The gates are highlighted in grey color. Gates marked with “Bg” represent the background gates used for subtraction.

Figure 2

Contributions of the different spectra for the analyzed spectrum of ${}^{192}\mathrm{Pb}$ decay. See Fig. 1 for details on the gates.

Figure 3

Comparison of the analyzed and reconstructed spectrum after the analysis for the ${}^{192}\mathrm{Pb}$ decay (a) and the deduced feeding distribution (b).

Figure 4

(a) Comparison of the analyzed and reconstructed spectrum after the analysis for the ${}^{190}\mathrm{Pb}$ decay and (b) the feeding distribution deduced from the analysis.

Figure 5

Comparison of the accumulated strength for the beta decays of ${}^{192,190}\mathrm{Pb}$ with theory.