Direct observation of the ${}^{114}\mathrm{Ba}\to {}^{110}\mathrm{Xe}\to {}^{106}\mathrm{Te}\to {}^{102}\mathrm{Sn}$ triple $\alpha$-decay chain using position and time correlations

The triple $\alpha$-decay chain ${}^{114}\mathrm{Ba}\to {}^{110}\mathrm{Xe}\to {}^{106}\mathrm{Te}\to {}^{102}\mathrm{Sn}$ has been directly observed for the first time, following the ${}^{58}\mathrm{Ni}\left({}^{58}\mathrm{Ni},2n\right)$ reaction. Implantation of ${}^{114}\mathrm{Ba}$ nuclei into a double-sided silicon-strip detector has allowed their $\alpha$ decays to be correlated in position and time with the $\alpha$ decays of the daughter $\left({}^{110}\mathrm{Xe}\right)$ and granddaughter $\left({}^{106}\mathrm{Te}\right)$ nuclei. In total, 17 events have been assigned to the ${}^{114}\mathrm{Ba}\to {}^{110}\mathrm{Xe}\to {}^{106}\mathrm{Te}\to {}^{102}\mathrm{Sn}$ triple $\alpha$-decay chain. The energy of the ${}^{114}\mathrm{Ba} \alpha$ decay has been measured to be $E_{\alpha }=3480$(20) keV, which is 70 keV higher than the previously measured value, and the half-life of ${}^{114}\mathrm{Ba}$ has been measured with improved accuracy, to be ${380}_{-110}^{+190}$ ms. A revised $Q_{{}^{12}\mathrm{C}}$ value of 19 035(45) keV for ${}^{114}\mathrm{Ba}$ is presented.

Figure 1

A chart showing the $\alpha$-emitting ${}_{52}\mathrm{Te},{}_{53}\mathrm{I},{}_{54}\mathrm{Xe},{}_{55}\mathrm{Cs}$, and ${}_{56}\mathrm{Ba}$ nuclei in the region above the $N\simeq Z\simeq 50$ shell closures. For each nucleus, the half-life and the $\alpha$-decay branching ratio are given. The shaded ${}_{50}\mathrm{Sn}$ and ${}_{51}\mathrm{Sb}$ nuclei represent the end points of the $\alpha$-decay chains; these nuclei decay by ${\beta }^{+}$ emission. Nuclei in the ${}^{114}\mathrm{Ba}\to {}^{110}\mathrm{Xe}\to {}^{106}\mathrm{Te}\to {}^{102}\mathrm{Sn}$ decay chain, of interest in this work, are marked with thick black borders. The proximity to $Z=50$ and to the $N=Z$ line is shown.

Figure 2

Energy spectra from the DSSDs. Panels (a), (b), and (c) show the energies of the first $\left({\alpha }_1\right)$, second $\left({\alpha }_2\right)$, and third $\left({\alpha }_3\right)$ decays when it is required that the decays occur following an implant, in the same pixel, and that ${\alpha }_3$ occurs within 0.3 ms of ${\alpha }_2$. The values written vertically on the panels give the energies associated with selected channels, not the centroids.

Figure 3

The distributions of time differences between successive events in the DSSDs. Panel (a) shows the time differences between the implanted recoil $(r_1$; ${}^{114}\mathrm{Ba})$ and the first decay $\left({\alpha }_1\right)$. Panels (b) and (c) show the time differences between the first $\left({\alpha }_1\right)$ and second $\left({\alpha }_2\right)$ decays and between the second $\left({\alpha }_2\right)$ and third $\left({\alpha }_3\right)$ decays, respectively. The triangles on panel (a) label the data points which have been subjected to the condition that there must be a time difference of at least 1.6 s between the two implantation events immediately prior to the decay events, as described in the text. The dotted lines are calculated using the extracted half-lives, intended to show the decay behavior; they are not fits to the data.

Figure 4

The logarithmic decay-time distribution of all 17 events attributed to the ${}^{114}\mathrm{Ba}\to {}^{110}\mathrm{Xe}\alpha$ decay. The curve shows the calculated logarithmic decay-time distribution as defined in Ref. [28] and the units on the vertical axis are arbitrary.