New isotope 227Rn and revised halflives for 223Rn and 226Rn

Neutron-rich isotopes of radon, produced by spallation reactions in a ThC2 target and selected chemically, were mass-separated and used as samples for radiation counting experiments. Assignments of the activities to radon isotopes were confirmed by genetic relationships to the previously known francium daughters. The halflife for the new isotope 227Rn is 23±1 s and that for 226Rn is 7.4±0.1 min. X-rays, γ-rays, and conversion electrons from the 223Rn activity were measured. The decay patterns of K X-rays and known gamma transitions in the 223Fr daughter yield a halflife of 23.2±0.4 min for 223Rn, in contrast to the value of 43±5 min reported earlier. Energies, intensities, and likely multipolarities for the most prominent gamma transitions in the 223Rn→223Fr decay are presented. (orig.)