Electron capture and positron decay of Fr206 and Fr208 and the energy levels of Rn206 and Rn208

The isotopes Fr206 and Fr208 were produced by the reactions Ir(Ne20,xn)Fr206,208 and mass separated on-line. The electron-capture and positron decays to Rn206 and Rn208 were studied by collecting ray and internal conversion electron singles spectra as a function of decay time as well as -, -e-, and -x ray coincidence spectra. The energies and many of the spins were determined for 18 excited, even parity states in Rn208 and for 10 excited, even parity states in Rn206. These nuclei appear to be excellent candidates for interpretation in terms of a weak coupling shell model. The energy levels were also compared to the predictions of the interacting boson approximation model. RADIOACTIVITY Fr206,208 from mass separated products of Irnat(Ne20,xn)Fr206,208. Measured E, ICC, - t, e - t. Deduced levels E, J, in Rn206,208.