The perturbation of a γγ directional correlation of75As in gaseous H275Se sources
Using gaseous H275Se sources the γγ directional correlation of the 121.0–279.5 keV γγ cascade of75As was measured as a function of pressure. The attenuation coefficientG2 varied between 0.67 and 0.96 for pressures between 0.1 and 200 Torr. Since the perturbation of the directional correlation is caused by hyperfine interaction of the highly charged ion formed after electron capture, the pressure dependence may be understood as being mainly due to changes of the charge states during collisions with neutral molecules. A simple model is proposed yielding a reasonable fit to the experimental data.