Direct mass measurements on the superallowed emitter 74Rb and its daughter 74Kr:: Isospin-symmetry-breaking correction for standard-model tests -: art. no. 072502

The decay energy of the superallowed beta decay Rb-74(beta(+))Kr-74 was determined by direct Penning trap mass measurements on both the mother and the daughter nuclide using the time-of-flight resonance technique and was found to be Q=10 416.8(4.5) keV. The exotic nuclide Rb-74, with a half-life of only 65 ms, is the shortest-lived nuclide on which a high-precision mass measurement in a Penning trap has been carried out. Together with existing data for the partial half-life as well as theoretical corrections, the decay energy yields a comparative half-life of Ft=3084(15) s for this decay, in agreement with the mean value for the series of the lighter nuclides from C-10 to Co-54. Assuming conserved vector current, this result allows for an experimental determination of the isospin-symmetry-breaking correction delta(C).