Investigation of the decay of 211Rn to 211At and the three-particle configuration in 211At

The gamma-gamma directional correlations for ten cascades observed in the decay of 211Rn were measured by means of a multi-detector system (seven Ge(Li) detectors). Together with the experimental data on the internal conversion of electrons this allowed a unique and model-independent assignment of the spin values for eight levels in 211At. Multipole mixing ratios for seven gamma transitions were also derived. The properties of 211At were treated in the framework of the multi-particle shell model using finite-range forces. The influence of core collective vibrations on the electromagnetic properties was taken into account by using the effective electromagnetic operators.