Hyperfine interactions and charge distributions of actinide ions recoiling into vacuum

The angular distribution of conversion electrons from the 4⁺→2⁺ transition in the ground-state rotational band of²⁴⁰Pu has been measuredvia the²³⁸U (α,2n)²⁴⁰Pu reaction. The electrons are emitted in flight from the Pu nuclei recoiling into vacuum atv/c?0.2%. The attenuation of the angular distribution by extranuclear fields is found to be less than 20% within 120 ps. The hyperfine interactions are discussed with particular attention to the high charge states of actinide recoil ions following internal conversion. Charge distributions ranging up to 45⁺ have been observed for²⁴⁰Cm nuclei in the²³⁹Pu(α,3n) reaction.