Beta strength distributions in neutron-deficient Kr and Sr isotopes using a total absorption spectrometer

Far from the line of stability, beta -decay studies are often a primary source of information on nuclear structure. The measured beta -strength distribution for a given decay can be used to verify the accuracy of our theoretical description of the parent nucleus ground state and the states populated in the daughter nucleus. Total absorption spectrometers based on large NaI crystals are well suited tools to determine the beta -strength distribution over the whole Q /sub EC/ decay window. The newly built spectrometer TAgS, dedicated to such studies, is presented and its performances and possibilities are discussed in the light of experiments performed at the ISOLDE /CERN mass separator. The resulting information on ground state deformations for the /sup 74/Kr and /sup 76/Sr isotopes are discussed. (22 refs).