First Experimental Determination of the Charge Radius of 74Rb and Its Application in Tests of the Unitarity of the Cabibbo-Kobayashi-Maskawa Matrix

Collinear-laser spectroscopy with the bunched-beams technique was used for the study of neutron deficient Rb isotopes, out to Rb-74 (N = Z = 37) at TRIUMF. The measured hyperfine coupling constants of Rb-76,Rb-78m were in agreement with literature values. The nuclear spin of Rb-75 was confirmed to be I = 3/2, and its hyperfine coupling constants were measured for the first time. The mean-square charge radius of Rb-74 was determined for the first time. This result has improved the isospin symmetry breaking correction term used to calculate the Ft value, with implications for tests of the unitarity of the Cabibbo-Kobayashi-Maskawa matrix.