Precise Q value measurements of ${}^{112,113}$Ag and ${}^{115}$Cd with the Canadian Penning trap for evaluation of potential ultra-low Q value $\beta$-decays

Abstract

An ultra-low Q value $\beta$-decay can occur from a parent nuclide to an excited state in the daughter with $Q_{UL}$ <1 keV. These decays are of interest for nuclear $\beta$-decay theory and as potential candidates in neutrino mass determination experiments. To date, only one ultra-low Q value $\beta$-decay has been observed -- that of ${}^{115}$In with $Q_{\beta }$ = 147(10) eV. A number of other potential candidates exist, but improved mass measurements are necessary to determine if the decays are energetically allowed and, in fact, ultra-low. We performed precise $\beta$-decay Q value measurements of ${}^{112,113}$Ag and ${}^{115}$Cd and combined them with nuclear energy level data for the daughter isotopes to determine if the potential UL Q value $\beta$-decay branches of ${}^{112,113}$Ag and ${}^{115}$Cd are energetically allowed and <1 keV. The Canadian Penning Trap at ANL was used to measure the cyclotron frequency ratios of singly-charged ${}^{112,113}$Ag and ${}^{115}$Cd ions with respect to their daughters. From these measurements, the ground-state $\beta$-decay Q values were obtained. The ${}^{112}$Ag, ${}^{113}$Ag, and ${}^{115}$Cd $\beta$-decay Q values were measured to be 3990.16(22) keV, 2085.7(4.6) keV, and 1451.36(34) keV, respectively. These results were compared to energies of excited states in ${}^{112}$Cd at 3997.75(14) keV, ${}^{113}$Cd at 2015.6(2.5) and 2080(10) keV, and ${}^{115}$In at 1448.787(9) keV, resulting in $Q_{\text{UL}}$ values of --7.59(26) keV, 6(11) keV, and 2.57(34) keV, respectively. The potential UL Q value decays of ${}^{112}$Ag and ${}^{115}$Cd have been ruled out. ${}^{113}$Ag is still a possible candidate until a more precise measurement of the 2080(10) keV, 1/2${}^{+}$ state of ${}^{113}$Cd is available. In the course of this work we have found the ground state mass of ${}^{113}$Ag reported in the 2020AME to be lower than our measurement by 69(17) keV (a 4$\sigma$ discrepancy).

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Cited by in corpus (7)

• Updated evaluation of potential ultra-low Q value $\beta$-decay candidates
• High-precision Penning-trap mass measurements of Cd and In isotopes at JYFLTRAP remove the fluctuations in the two-neutron separation energies
• Identification of a potential ultra-low Q value electron capture decay branch in ${}^{75}$Se via a precise Penning trap measurement of the mass of ${}^{75}$As
• High-precision measurements of the atomic mass and electron-capture decay $Q$ value of ${}^{95}$Tc
• Ultra-low $Q_{\beta }$ value for the allowed decay of ${}^{110}$Ag${}^m$ confirmed via mass measurements
• High-precision direct decay energy measurements of the electron-capture decay of ${}^{97}$Tc
• Probing the quantum phase transition around $N\approx 60$ via mass measurements of technetium isotopes