Proposal to the Isolde and Neutron Time-of-Flight Committee PRECISION STUDY OF THE BETA DECAY OF 74Rb.

We are proposing a high-resolution study of the beta decay of 74Rb in order to extrapolate our precision knowledge of the superallowed beta decays from the sd and fp shells towards the medium-heavy Z=N nuclei. The primary goal is to provide new data for testing the CVC hypothesis and the unitarity condition of the CKM matrix of the Standard Model. The presented programme would involve the careful measurements of the decay properties of 74Rb including the branching ratios to the excited states as well as the precise determination of the decay energy of 74Rb. The experimental methods readily available at ISOLDE include high-transmission conversion electron spectroscopy, gamma-ray spectroscopy as well as the measurements of the masses of 74Rb and 74Kr using two complementary techniques, ISOLTRAP and MISTRAL. The experiment would rely on a high-quality 74Rb beam available at ISOLDE with adequate intensity. New physical phenomena associated with nuclear structure and decays along the Z = N line are expected to arise due to the equal filling of the proton and neutron states, as well as due to th