Hyperfine interactions in isolated ions

The nature of the hyperfine interaction in free ions recoiling at high velocity out of solid targets has been established in recent years as a largely static interaction in all regions of the periodic table that were investigated. The frequency spectrum in heavy ions can be approximated by the sum of a Lorenzian centered at zero and cut off at high frequencies, and a constant, hard core, component. This detailed information is of great value now for the study and interpretation of tilted foil measurements. In these measurements ions recoil out of carbon foils at large angles to the normal to the foil and it has been established that large, polarized magnetic fields evolve in these ions and act on the nuclei in their interior. It has also been established that tilted foil measurements can serve as valuable tools for determining the values and signs of the magnetic moments of short-lived nuclear states. In particular, it has been shown recently that the asymmetry in the angular distribution of deexitation gammas can be enhanced considerably with multifoil arrays and a pattern is established which comes close to a free precession around the tilt axis. (orig.)