Evidence of the Finite Boson Number from Lifetime Measurements in 78Kr and 79Rb

At the first Erice Meeting on Interacting Bosons, Gelberg and Kaup1 presented an interpretation of the ground state and γ bands of the even Kr isotopes in terms of IBA-2 2. They recognized that the spectra change from that of the rather strongly deformed 74,76 Kr to the γ-unstable shapes of the 80,82 Kr isotopes. These fits required remarkably few force constants; furthermore, it was found that all interaction parameters remained essentially constant, except for the quadrupole term Xπ and the boson number Nπ which varied linearly with the neutron number.