Resonance behaviour of a perturbed gamma gamma directional correlation in a magnetic field

Using a gaseous H₂ ⁷⁵Se source at low pressure the perturbed directional correlation of the 121–279 keVγγ cascade of⁷⁵As was measured as a function of an external magnetic field. The anisotropy shows a pronounced resonance behaviour around zero field. This effect may be understood as being due to the hyperfine interaction of the nucleus with the electronic shell of the highly charged ion formed after electron capture. The charge distribution of the As ions was estimated and the spin distribution derived from it. Then a comparison with the theory of Leisi was possible giving a qualitative agreement between theory and experiment.