PRECISION SPECTROSCOPY ON SIMPLE AND COMPLEX ATOMIC IONS IN TRAPS

We discuss the Ca+ ion as a ''simple'' atomic system, described as an electronic three-level system. In a Paul ion trap a small ion cloud ca n be laser cooled until crystallisation appears which reduces the ion motion. Lifetime and hyperfine structure measurements in ground and ex cited electronic states can be performed with high precision. A first example for the investigation of a ''complex'' ionic system is represe nted by the Eu+ ion, where hyperfine structure splittings have been ob tained with uncertainties in the 10(-9) range even on radioactive isot opes with few available particles. These small uncertainties require e xtensive and complicated pertubation calculation for a determination o f coupling constant, but open the way for detailed investigation of nu clear structure effects.