New Data on the Relaxed Excited State of theFCenter

Ionization energies $\Delta E$ and lifetimes ${\tau }_R$ of the excited state of the $F$ center have been measured in various alkali halides. The experimental values of $\Delta E$ have been plotted versus ($\frac{m^{*}}{m}$) ($\frac{1}{{{\epsilon }_S}^2}$), following Fowler's idea that in emission the excited-state wave function is very broad. The hydrogenic model seems to fit the data very well, and Fowler's theory finds strong experimental support.