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Register a new userDirect determination of the $^{138}$La $beta$-decay $Q$ value using Penning trap mass spectrometry
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Background: The understanding and description of forbidden decays provides interesting challenges for nuclear theory. These calculations could help to test underlying nuclear models and interpret experimental data. Purpose: Compare a direct measurement of the $^{138}$La $beta$-decay $Q$ value with the $beta$-decay spectrum end-point energy measured by Quarati et al. using LaBr$_3$ detectors [Appl. Radiat. Isot. 108, 30 (2016)]. Use new precise measurements of the $^{138}$La $beta$-decay and electron capture (EC) $Q$ values to improve theoretical calculations of the $beta$-decay spectrum and EC probabilities. Method: High-precision Penning trap mass spectrometry was used to measure cyclotron frequency ratios of $^{138}$La, $^{138}$Ce and $^{138}$Ba ions from which $beta$-decay and EC $Q$ values for $^{138}$La were obtained. Results: The $^{138}$La $beta$-decay and EC $Q$ values were measured to be $Q$ = 1052.42(41) keV and $Q_{EC}$ = 1748.41(34) keV, improving the precision compared to the values obtained in the most recent atomic mass evaluation [Wang, et al., Chin. Phys. C 41, 030003 (2017)] by an order of magnitude. These results are used for improved calculations of the $^{138}$La $beta$-decay shape factor and EC probabilities. New determinations for the $^{138}$Ce 2EC $Q$ value and the atomic masses of $^{138}$La, $^{138}$Ce, and $^{138}$Ba are also reported. Conclusion: The $^{138}$La $beta$-decay $Q$ value measured by Quarati et al. is in excellent agreement with our new result, which is an order of magnitude more precise. Uncertainties in the shape factor calculations for $^{138}$La beta-decay using our new $Q$ value are reduced by an order of magnitude. Uncertainties in the EC probability ratios are also reduced and show improved agreement with experimental data.
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Background: Ultra-low $Q$-value $beta$-decays are interesting processes to study with potential applications to nuclear $beta$-decay theory and neutrino physics. While a number of potential ultra-low $Q$-value $beta$-decay candidates exist, improved mass measurements are necessary to determine which are energetically allowed. Method: Penning trap mass spectrometry was used to determine the atomic mass of $^{89}$Y and $^{139}$La, from which $beta$-decay $Q$-values for $^{89}$Sr and $^{139}$Ba were obtained to determine if there could be an ultra-low $Q$-value decay branch in the $beta$-decay of $^{89}$Sr $rightarrow$ $^{89}$Y or $^{139}$Ba $rightarrow$ $^{139}$La. Results: The $^{89}$Sr $rightarrow$ $^{89}$Y and $^{139}$Ba $rightarrow$ $^{139}$La $beta$-decay $Q$-values were measured to be $Q_{rm{Sr}}$ = 1502.20(0.35) keV and $Q_{rm{Ba}}$ = 2308.37(68) keV. These were compared to energies of excited states in $^{89}$Y at 1507.4(1) keV, and in $^{139}$La at 2310(19) keV and 2313(1) keV to determine $Q$-values of -5.20(37) keV for the potential ultra-low $beta$-decay branch of $^{89}$Sr and -1.6(19.0) keV and -4.6(1.2) keV for those of $^{139}$Ba. Conclusion: The potential ultra-low $Q$-value decay branch of $^{89}$Sr to the $^{89}$Y (3/2$^-$, 1507.4 keV) state is energetically forbidden and has been ruled out. The potential ultra-low $Q$-value decay branch of $^{139}$Ba to the 2313 keV state in $^{139}$La with unknown J$^{pi}$ has also been ruled out at the 4$sigma$ level, while more precise energy level data is needed for the $^{139}$La (1/2$^+$, 2310 keV) state to determine if an ultra-low $Q$-value $beta$-decay branch to this state is energetically allowed.
A commercial, position-sensitive ion detector was used for the first time for the time-of-flight ion-cyclotron resonance detection technique in Penning trap mass spectrometry. In this work, the characteristics of the detector and its implementation in a Penning trap mass spectrometer will be presented. In addition, simulations and experimental studies concerning the observation of ions ejected from a Penning trap are described. This will allow for a precise monitoring of the state of ion motion in the trap.
Penning trap measurements using mixed beams of 100Mo - 100Ru and 76Ge - 76Se have been utilized to determine the double-beta decay Q-values of 100Mo and 76Ge with uncertainties less than 200 eV. The value for 76Ge, 2039.04(16) keV is in agreement with the published SMILETRAP value. The new value for 100Mo, 3034.40(17) keV is 30 times more precise than the previous literature value, sufficient for the ongoing neutrinoless double-beta decay searches in 100Mo. Moreover, the precise Q-value is used to calculate the phase-space integrals and the experimental nuclear matrix element of double-beta decay.
The cyclotron frequency ratio of $^{187}mathrm{Os}^{29+}$ to $^{187}mathrm{Re}^{29+}$ ions was measured with the Penning-trap mass spectrometer PENTATRAP. The achieved result of $R=1.000:000:013:882(5)$ is to date the most precise such measurement performed on ions. Furthermore, the total binding-energy difference of the 29 missing electrons in Re and Os was calculated by relativistic multiconfiguration methods, yielding the value of $Delta E = 53.5(10)$ eV. Finally, using the achieved results, the mass difference between neutral $^{187}$Re and $^{187}$Os, i.e., the $Q$ value of the $beta^-$ decay of $^{187}$Re, is determined to be 2470.9(13) eV.
We report the first direct measurement of the $^{14}text{O}$ superallowed Fermi $beta$-decay $Q_{EC}$-value, the last of the so-called traditional nine superallowed Fermi $beta$-decays to be measured with Penning trap mass spectrometry. $^{14}$O, along with the other low-$Z$ superallowed $beta$-emitter, $^{10}$C, is crucial for setting limits on the existence of possible scalar currents. The new ground state $Q_{EC}$ value, 5144.364(25) keV, when combined with the energy of the $0^+$ daughter state, $E_x(0^+)=2312.798(11)$~keV [Nucl. Phys. A {bf{523}}, 1 (1991)], provides a new determination of the superallowed $beta$-decay $Q_{EC}$ value, $Q_{EC}(text{sa}) = 2831.566(28)$ keV, with an order of magnitude improvement in precision, and a similar improvement to the calculated statistical rate function $f$. This is used to calculate an improved $mathcal{F}t$-value of 3073.8(2.8) s.
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