OPTICAL STUDIES OF COMPLEX COLOR-CENTERS IN KF CRYSTALS

A detailed investigation on F-aggregate centers in KF crystals has been performed by means of optical absorption and luminescence measurements. The spectroscopic features of the absorption bands due to F3 and F4 defects were confirmed and studied as a function of temperature. Two new emission bands at 958 and 1180 nm were detected, and their dependence on the excitation wavelength and temperature was determined. Assignment of the 958 nm luminescence as due to F3 centers and of the 1180 nm luminescence to F4 defects is proposed according to the results of excitation spectra. A remarkable influence of the crystal preparation on the optical properties of color centers in KF has been evidenced