Optical Absorption byFCenters in Alkali Halides

Abstract

The integrated optical absorption due to $F$ centers in KCl, KBr, and NaCl has been measured using a modification of Kleinschrod's method which eliminates salt-effect errors. Assuming the validity of the $f$ sum rule, the results are used to obtain experimental values for the local field correction. The Onsager local field gives better agreement with experiment than does the classical expression of Lorentz. To facilitate comparison with other work the results have also been used to compute oscillator strengths using Smakula's equation. The $f$ values are 0.91±0.12, 0.85±0.08, and 0.86±0.05 for KCl, KBr, and NaCl, respectively.