Energy Distribution of External Photoelectrons from F-Centers in RbI

摘要: Energy distributions of the external photoelectrons from $F$-centers in RbI were determined by retarding-potential techniques. Precautions taken to secure electrically uniform surfaces. The then emerged two separable groups. first, termed $f$-group, was composed relatively fast electrons that attributed direct photon ionization $F$-centers. Photoelectron energies distributed a band, roughly gaussian form, treated according theory given Herring. Franck-Condon principle into account; scattering excited neglected. second group photoelectrons, $s$-group, comparatively slow. energy distribution had an unusual form and peaked at surprisingly low value 0.3 or 0.4 ev, independent $h\ensuremath{\nu}$. Exciton-enhanced emission almost entirely this type. Three factors may influence $s$-type are mentioned: Hebb's calculations indicate lattice exciton-induced be important because large depth origin these photoelectrons. As suggested Seitz, degradation exciton prior $F$-center stimulation involved. Finally, some $s$-group arise other types centers.