Direct mass measurements of cadmium and palladium isotopes and their double-$\beta$ transition $Q$ values

The $Q$ value of the double-electron capture in ${}^{108}$Cd has been determined to be (272.04 $\pm$ 0.55) keV in a direct measurement with the double-Penning trap mass spectrometer TRIGA-TRAP. Based on this result a resonant enhancement of the decay rate of ${}^{108}$Cd is excluded. We have confirmed the double-$\beta$ transition $Q$ values of ${}^{106}$Cd and ${}^{110}$Pd recently measured with the Penning-trap mass spectrometers SHIPTRAP and ISOLTRAP, respectively. Furthermore, the atomic masses of the involved nuclides (${}^{106,108,110}$Cd, ${}^{106,108,110}$Pd) have been directly linked to the atomic mass standard.

Figure 1

Individual cyclotron-frequency ratios $r$ measured for the $Q$-value determination for (a) ${}^{106}$Cd-${}^{106}$Pd, (b) ${}^{108}$Cd-${}^{108}$Pd, and (c) ${}^{110}$Pd-${}^{110}$Cd. The central lines show the average cyclotron-frequency ratios, and the grey bands are their 1$\sigma$ uncertainties.