Production of Photochromic Bands from Dipole Centers in Irradiated CaF2:Ce

The method of ionic thermocurrents has been combined with optical-absorption and radiation-damage techniques to investigate the production of photochromic centers in Ca${\mathrm{F}}_2$:Ce. It is found that the initial growth of the photochromic bands under x irradiation is correlated with the destruction of the 243-nm band initially, and with an exponential decay of dipole centers at later stages. The maximum oscillator strength of the 243-nm band is calculated. It is also found that one photochromic center is formed for each four dipole centers destroyed, independent of dose rate.