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

TL;DR

This paper establishes new experimental limits on the half-lives of several rare and unexplored double beta decay isotopes, including $^{146}$Nd and $^{144}$Sm, using indirect methods and accelerator mass spectrometry.

Contribution

It provides the first or improved limits on half-lives for multiple unexplored 2$eta$ decay isotopes, expanding knowledge of their decay properties.

Findings

Limits on $^{146}$Nd 2$eta$ decay half-life ($ extgreater 3 imes 10^9$ yr)

Limits on $^{146}$Sm 2$eta$ decay half-life ($ extgreater 4.5 imes 10^{19}$ yr)

First constraints on $^{144}$Sm 0$ uetaeta$ decay half-life ($ extgreater 10^{15}$ yr)

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 ($T^{\beta\beta}_{1/2} \gsim 3 \times 10^9$ yr) or direct search for $^{146}$Sm with accelerator mass spectrometers ($T^{\beta\beta}_{1/2} \gsim 4.5 \times 10^{19}$ 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 $T^{0\nu\epsilon\beta^+}_{1/2} \gsim 10^{15}$ yr for the unexplored $^{144}$Sm $0\nu\epsilon \beta^+$ decay may be obtained from the data of a GSO crystal scintillator.