An Experimental Proof of Radiative Recombination Mechanisms of Electron‐Hole Pairs at Activator Ions

It has been shown that the concentration dependence curve of activator luminescence provides us with a powerful tool in studying cathodoluminescence. The experimental results reveal the excitation mechanisms of activator ions by irradiation of electron beam on phosphor crystals; two excitation mechanisms should be considered: ( i ) direct excitation by incident electrons, including internally generated secondary electrons; and ( ii ) indirect excitation through the mobile electron and holes generated by incident electrons. The experimental results also suggest a possible model that ( iii ) radiative recombination of electron‐hole pairs only occurs at the activator ions showing two valences at the ordinary conditions, and ( iv ) the type of radiative recombination process at the activator ions is determined by the type of carrier which is first trapped.