Photoconductivity in α-lead azide crystals

Abstract

The photocurrent produced in α-lead azide by continuous irradiation has been measured as a function of the wavelength and intensity of the light, of temperature, and of time. The peak at 4070 Å has been interpreted as a transition from the valence band to an exciton level, which, from temperature-coefficient measurements, lies 8.2 kcal/mole below the conduction band. The total thermal band gap is estimated to be 37 kcal/mole. The peak at 4800 Å is regarded as due to electron promotion from impurity levels to a pre-dissociation level close to the conduction band, and the concentration of these impurity levels has been measured.