Ultraviolet Absorption Spectra ofin Alkaline-Earth Fluorides
- 10 February 1967
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review B
- Vol. 154 (2), 270-276
- https://doi.org/10.1103/physrev.154.270
Abstract
The ultraviolet absorption spectra of , 0.005%, in crystals of the alkaline-earth fluorides Ca, Sr, and Ba have been measured at both room and liquid-nitrogen temperatures. The general features in the spectra of all three hosts are similar. The ultraviolet spectra of , 0.005% to 5%, in Ca show three regions of interconfigurational absorption which may be assigned as: (1) bands from about 31 000 to 56 000 , with half-width about 2000 at concentration ∼%; (2) weak and broad band from 60 000 to about 77 000 with maximal absorption at about 70 000 ; and (3) a charge-transfer absorption, , appearing as an apparent red shift of the absorption edge of the host Ca at approximately 80 000 . The assignments of these three regions of absorption are based on the location, width, number, oscillator strength, and temperature dependence of the bands. The effect of large concentration, ≥0.1%, on the uv absorption spectra of is interpreted as the result of cluster formation from pairs of -interstitial . The vibronic structure in the lowest band may be conceived in terms of pseudolocalized vibrations, as in the case of several divalent rare-earth ions in alkali halides treated by Wagner and Bron.
Keywords
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