Oxygen- and Hydrogen-Containing Impurity in Laser-Active Matrices of Alkali and Alkaline-Earth Metal Fluorides

Abstract

crystals not subjected to irradiation or photo and thermal treatment. LiF:Co, LiF:Ni, NaF:Co, MgF2:Co, and MgF2:Ni crystals grown by the Czochralski method with addition of СoF2 and NiF2 in the melt were investigated. The absorption spectra were measured in the visible and infrared ranges of the spectrum with Specord UVVIS and IFS25 spectrophotometers at room temperature. Bands characteristic of bivalent Co and Ni ions (6, 7) were observed in the spectra recorded in the visible range. In the IR spectra of the examined crystals, wide bands were observed in the range 2500-3750 cm -1 and no absorption bands corresponding to valence vibrations of single anion-substituting OHor OHions distorted with impurity cations were detected in the range 3500-3740 cm -1 . Figure 1 shows the spectrum of the LiF:Co crystal (curve 1) in which the band between 2500 and 3700 cm -1 is well pronounced together with the spectrum of the LiF:Co crystal γ-irradiated with a doze of 10 8 R (curve 2). As already pointed out above, bands in the range 2500-3700 cm -1 were caused by molecular complexes with the Н-bond previously observed only in irradiated or irradiated and thermally treated crystals. From Fig. 1 (curve 2) it can also be seen that crystal complexes with the Н-bond absorbing in the range 2500-3700 cm -1 decompose after γ-irradiation . These complexes behave analogously when they are formed on irradiation of alkali fluoride crystals with hydroxyl (Fig. 2) (8). Curve 1 in Fig. 2 shows the spectrum of the initial LiF:ОН, Мg crystal, curve 2 shows the spectrum of the crystal irradiated with a doze of 10 7 R, and curve 3 shows the spectrum of the crystal γ-irradiated with a doze of 10 8 R. It can be seen that defects with the 2500-3700 cm -1 absorption band first are formed and then decay as the irradiation doze increases, and the 1900-2200 cm -1 absorption band subsequently arises. The identical behavior of bands (ν 3700 cm -1 ) for irradiated crystals with hydroxyl and initial crystals grown and investigated by us allows us to conclude that the observed bands can be caused by analogous molecular complexes with the Н-bond.