The F 2 + Center in KCl Crystals Part I: Formation and Bleaching Kinetics

A quantitative analysis of the higher transitions of the M center in the UV up to 5.0 eV in KCl crystals with high [M] : [F] ratio and unaligned and aligned M centers shows several new excitations (“L M bands”). Assuming that the L M excitation leads to conductive states, a simple electron kinetic model shows that UV irradiation of the F + M center system produces ionized F and M centers (α and F   2 + ) while competing capture processes partially destroyed them or form F' and M' centers. The F   2 +center production spectrum should closely follow the absorption ratio of L M :L F while the bleaching spectrum should follow the F' and M' spectrum. Experimental confirmation of this model is presented. By X‐raying the crystal (containing F + M centers) at LHeT, extra electron traps are introduced into the crystal and shift the equilibrium of the reaction to higher amount of F   2 +center, which are not stabilized by F' and M' centers. These extra F   2 +centers anneal out near 40 °K in parallelity with the third stage annealing of X‐ray produced α‐centers‐interstititals anions.