The electronic properties of the $F$ center are considered on the basis of a semicontinuum model. It is shown that calculated absorption and emission energy levels and strengths agree closely with experimental values for NaCl, provided that certain reasonable values of parameters are chosen in the calculation. The resulting excited $2p$ state from which emission occurs has a very diffuse wave function, its maximum being at ≈4-5 nearest-neighbor distances, while the wave function of the ground state into which emission occurs remains largely confined to the potential well. This picture of the emitting system is consistent with a number of other experimental results, notably the emission associated with $F_A$ centers.

• Received 20 April 1964

DOI:https://doi.org/10.1103/PhysRev.135.A1725