Penning trap mass spectrometry Q-value determinations for highly forbidden $\beta $-decays

Over the last several decades, extremely sensitive, ultra-low background beta and gamma detection techniques have been developed. These techniques have enabled the observation of very rare processes, such as highly forbidden beta decays e.g. of 113Cd, 50V and 138La. Half-life measurements of highly forbidden beta decays provide a testing ground for theoretical nuclear models, and the comparison of calculated and measured energy spectra could enable a determination of the values of the weak coupling constants. Precision Q-value measurements also allow for systematic tests of the beta-particle detection techniques. We will present the results and current status of Q value determinations for highly forbidden beta decays. The Q values, the mass difference between parent and daughter nuclides, are measured using the high precision Penning trap mass spectrometer LEBIT at the National Superconducting Cyclotron Laboratory.