Photoconduction in KBr and KI ContainingFCenters

Abstract

Photoconductivity in potassium bromide and potassium iodide containing $F$ centers has been investigated at 80°K. The product of the quantum yield and unit range has been measured over the spectral range from 2.0 to 5.8 ev with $F$-center concentrations between ${10}^{15}$ and ${10}^{17}$ ${\mathrm{cm}}^{-3\mathrm{}}$. Evidence is presented that the mechanism for the production of photoelectrons depends upon the photon energy and the concentration of $F$ centers. Two mechanisms for the production of photoelectrons are suggested by the data: the ionization of $F$ centers by excitons and direct optical ionization of $F$ centers.