Observation of angular correlation between subsequently emitted Auger electrons

In an exploratory feasibility study we have measured the angular correlation between Auger electrons that were emitted in a cascadelike decay process after resonant photoexcitation, using synchrotron radiation from the Brookhaven National Synchrotron Light Source. While the monochromator was tuned to the argon 1s→4p resonance (3203.5 eV) we recorded Ar LMM Auger electrons in coincidence with KL_2,3L_2,3,KL₁L_2,3, and KL_2,3M_1,2,3 Auger electrons. We found different nonisotropic angular correlations between distinct energy regions of the LMM group of Auger lines and the KL_2,3L_2,3 Auger electrons, while for other kinetic energies the LMM Auger electrons exhibit isotropy. Because the KLL and LMM Auger energies are so different, we believe that the nonisotropic angular correlation observed is due to an alignment effect rather than a dynamical postcollision interaction effect.