EPR study of the effect of ionizing radiation on chromium centers in Mg$_2$SiO$_4$ : Cr, Li laser crystals

Forsterite single crystals doped with chromium and lithium and exposed to ionizing radiation have been studied using multifrequency electron paramagnetic resonance (EPR) spectroscopy. It has been found that ionizing irradiation up to a dose of $10^8$ rad does not lead to a significant change in the concentration of single chromium impurity centers. At the same time, $\gamma$-ray irradiation of the crystal leads to a decrease in the concentration of active laser centers, which form an associate of trivalent chromium and monovalent lithium in the crystallographic positions $M2$ and $M1$, respectively, and to the formation of new centers of divalent chromium. The structure and magnetic properties of the new centers have been discussed.