Precise <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>Q</mml:mi></mml:math>-value measurements of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Ag</mml:mi><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>112</mml:mn><mml:mo>,</mml:mo><mml:mn>113</mml:mn></mml:mrow></mml:mmultiscripts></mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Cd</mml:mi><mml:mprescripts/><mml:none/><mml:mn>115</mml:mn></mml:mmultiscripts></mml:math> with the Canadian Penning trap for evaluation of potential ultralow <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>Q</mml:mi></mml:math>-value <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>β</mml:mi></mml:math> decays

Background: An ultralow $Q$-value $\ensuremath{\beta}$ decay can occur from a parent nuclide to an excited nuclear state in the daughter such that ${Q}_{\text{UL}}\ensuremath{\lesssim}$ 1 keV. These decay processes are of interest for nuclear $\ensuremath{\beta}$-decay theory and as potential candidates in neutrino mass determination experiments. To date, only one ultralow $Q$-value $\ensuremath{\beta}$ decay has been observed---that of $^{115}\mathrm{In}$ with ${Q}_{\ensuremath{\beta}}=147(10)$ eV. A number of other potential candidates exist, but improved mass measurements are necessary to determine if these decay channels are energetically allowed and, in fact, ultralow.Purpose: To perform precise $\ensuremath{\beta}$-decay $Q$-value measurements of $^{112,113}\mathrm{Ag}$ and $^{115}\mathrm{Cd}$ and to use them in combination with nuclear energy level data for the daughter isotopes $^{112,113}\mathrm{Cd}$ and $^{115}\mathrm{In}$ to determine if the potential ultralow $Q$-value $\ensuremath{\beta}$-decay branches of $^{112,113}\mathrm{Ag}$ and $^{115}\mathrm{Cd}$ are energetically allowed and $\ensuremath{\lesssim}1$ keV.Method: The Canadian Penning Trap at Argonne National Laboratory was used to measure the cyclotron frequency ratios of singly charged $^{112,113}\mathrm{Ag}$ and $^{115}\mathrm{Cd}$ ions with respect to their daughters $^{112,113}\mathrm{Cd}$ and $^{115}\mathrm{In}$. From these measurements, the ground-state to ground-state $\ensuremath{\beta}$-decay $Q$ values were obtained.Results: The $^{112}\mathrm{Ag}\phantom{\rule{4pt}{0ex}}\ensuremath{\rightarrow}\phantom{\rule{4pt}{0ex}}^{112}\mathrm{Cd}$, $^{113}\mathrm{Ag}\phantom{\rule{4pt}{0ex}}\ensuremath{\rightarrow}\phantom{\rule{4pt}{0ex}}^{113}\mathrm{Cd}$, and $^{115}\mathrm{Cd}\phantom{\rule{4pt}{0ex}}\ensuremath{\rightarrow}\phantom{\rule{4pt}{0ex}}^{115}\mathrm{In}\phantom{\rule{4pt}{0ex}}\ensuremath{\beta}$-decay $Q$ values were measured to be ${Q}_{\ensuremath{\beta}}(^{112}\mathrm{Ag})=3990.16(22)$ keV, ${Q}_{\ensuremath{\beta}}(^{113}\mathrm{Ag})=2085.7(4.6)$ keV, and ${Q}_{\ensuremath{\beta}}(^{115}\mathrm{Cd})=1451.36(34)$ keV. These results were compared to energies of excited states in $^{112}\mathrm{Cd}$ at 3997.75(14) keV, $^{113}\mathrm{Cd}$ at 2015.6(2.5) and 2080(10) keV, and $^{115}\mathrm{In}$ at 1448.787(9) keV, resulting in precise ${Q}_{\text{UL}}$ values for the potential decay channels of $\ensuremath{-}7.59(26)$ keV, 6(11) keV, and 2.57(34) keV, respectively.Conclusion: The potential ultralow $Q$-value decays of $^{112}\mathrm{Ag}$ and $^{115}\mathrm{Cd}$ have been ruled out. $^{113}\mathrm{Ag}$ is still a possible candidate until a more precise measurement of the 2080(10) keV, $1/{2}^{+}$ state of $^{113}\mathrm{Cd}$ is available. In the course of this work we have found the ground state mass of $^{113}\mathrm{Ag}$ reported in the 2020 Atomic Mass Evaluation [Wang et al., Chin. Phys. C 45, 030003 (2021)] to be lower than our measurement by 69(17) keV (a $4\ensuremath{\sigma}$ discrepancy).

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