On ${}^{146}$Nd, ${}^{144}$Sm and other unexplored 2$\beta$ decay isotopes

Abstract

${}^{146}$Nd is one of only four (over a total of 35 existing) 2${\beta }^{-}$ decay isotope candidates whose half-lives currently lack experimental limits. The $\alpha$ activity of the ${}^{146}$Sm daughter nuclide allows placement of limits on the 2$\beta$ decay using the ${}^{146}$Nd/${}^{142}$Nd abundance ratio ($T_{1/2}^{\beta \beta }\text{gsim}3\times 10^9$ yr) or direct search for ${}^{146}$Sm with accelerator mass spectrometers ($T_{1/2}^{\beta \beta }\text{gsim}4.5\times 10^{19}$ yr). With a similar approach, a modest ($\sim$ Gyr) first limit on half-lives for the other unexplored $2\beta$ unstable isotopes and competitive limits (few $10^{13}$yr) for ${}^{98}$Mo and ${}^{122}$Sn are also given. Finally, it is shown how the limit $T_{1/2}^{0\nu ϵ{\beta }^{+}}\text{gsim}10^{15}$ yr for the unexplored ${}^{144}$Sm $0\nu ϵ{\beta }^{+}$ decay may be obtained from the data of a GSO crystal scintillator.

Comments: 5 pages, 1 figure