Abstract
The number of magnetic centers in alkali halides additively colored in the alkali vapor has been determined by measuring the static magnetic susceptibility. Curie's law is followed, and the measurements have been extended to liquid helium temperatures to increase the sensitivity. The number of centers is compared with the optical absorption of the F band. Under the assumptions that the F-center electron wave function depends parametrically upon the coordinates of the surrounding nuclei, the electric dipole matrix element is independent of the nuclear coordinates, and the electric field at the electron is the Lorentz local field, the optical oscillator strengths for a Lorentz, Gaussian, and observed line shape are determined. The average for a series of experiments yield fL=0.66 for KCl, fL=0.71 for KBr, and fL=0.46 for KI. Values for CsBr and NaCl are discussed.