Windows and photocathodes for a high resolution solid state bandpass ultraviolet photon detector for inverse photoemission

We have measured the absolute quantum yield for alkali halides and the spectral transmission for alkaline earth fluoride windows to find an optimized bandpass combination for a solid state ultraviolet (UV) photon detector for inverse photoemission. The best resolution achieved is 0.33 eV (full width at half-maximum), being obtained with the NaCl photocathode–BaF2 window combination. This, however, leads to a rather low quantum efficiency of 0.3%. The combination NaCl–SrF2 chosen for our detector offers a resolution of 0.42 eV (full width at half-maximum) with a maximum quantum efficiency of 2.5% at 9.50 eV photon energy.