  The performance of cesium iodide as a reflective photocathode is presented.
The absolute quantum efficiency of a 500 nm thick film of cesium iodide has
been measured in the wavelength range 150 nm to 200 nm. The optical absorbance
has been analyzed in the wavelength range 190 nm to 900 nm and the optical band
gap energy has been calculated. The dispersion properties were determined from
the refractive index using an envelope plot of the transmittance data. The
morphological and elemental film composition have been investigated by atomic
force microscopy and X-ray photo-electron spectroscopy techniques.
