Optical Properties and Formation Kinetics of $M^{+}$ Centers in NaF

It is shown that the $M^{+}$ center in NaF has an absorption band at 740 mμ and an emission band at 943 mμ. $M^{+}$ centers in NaF can be produced by prolonged x irradiation at room temperature, or by irradiation at low temperature followed by annealing to near room temperature. From a study of the production and transformation of the $M$ and $M^{+}$ centers it is concluded that the formation of an $M$ center is preceded by the intermediate formation of an $M^{+}$ center. It is suggested that $M$ centers in NaF, as in LiF, are formed through the reaction $\alpha +F\to M^{+}$, followed by electron capture. The kinetics of aggregation to $M^{+}$ centers in NaF and LiF are also studied in the present work.