CsBr/Cr photocathodes were found [J. R. Maldonado et al., J. Vac. Sci. Technol. B 22, 3025 (2004); J. R. Maldonado et al., Proc. SPIE 5520, 46 (2003)] to meet the requirements of a multielectron beam lithography system operating with a light energy of 4.8 eV (257 nm). The fact that photoemission was observed With a light energy below the reported 7.3 eV band gap for CsBr was not understood. This article presents experimental results on the presence of intra-band-gap absorption sites (IBASs) in CsBr thin film photoelectron emitters, and presents a model based on IBAS to explain the observed photoelectron emission behavior at energies below band gap. A fluorescence band centered at 330 nm with a full width at half maximum of about 0.34 eV was observed in CsBr/Cr samples under 257 nm laser illumination, which can be attributed to IBAS and agrees well with previously obtained synchrotron photoelectron spectra [J. R. Maldonado et al., J. Vac. Sci. Tecimol. B 22, 3025 (2004)] from the valence band of CsBr films. (c) 2006 American Vacuum Society.