Recent results from the IS456 experiment at ISOLDE on the changes in the mean-square charge radii of the neutron-decient polonium isotopes using the in-source resonant laser spectroscopy technique with the RILIS has revealed that 191 Po is a key nucleus in the understanding of shape coexistence around 186 Pb104. Higher resolution is however required in order to determine the spin of the ground state (T1=2 = 22 ms) and of the long-lived high-spin isomer (T1=2 = 93 ms). Ground-state properties related to shape (changes in the mean-square charge radii, electric quadrupole moments) and to nuclear conguration (magnetic dipole moment) are also essential. We therefore propose to study 191 Po with the CRIS setup at ISOLDE. The limited production rates do not allow for this measurement to be performed with the existing facility; beam extraction developments and an upgrade of the incident proton beam energy to 2:0 GeV are necessary to improve the production rates. As a step toward this experiment at CRIS, we propose to do on-line preliminary work with 193;195;196;204 Po to ascertain the feasibility of this study.

The α decay of mass-separated202Rn is studied at the ISOLDE separator. Time sequential α-singles spectra together with α-X-t and α-e-t coincidence events are collected. Fine structure in the α decay is observed and feeding of a low-lying 0 2 + state at 816 keV in198Po is evidenced. This 0+ state can be interpreted as the bandhead of an intruder-state based deformed band, coexisting with the spherical groundstate band. Mixing between normal and intruder states is discussed. A preliminary α-decay study of200Rn did not yet reveal any fine structure.