* Work function of Al : 4.08 eV (~303.88 nm) (from Handbook of Chemistry and Physics) * The wavelength of the incident beam must be shorter than 303.88 nm for electron emission.

MgF(2)-overcoated aluminum films with high-vacuum ultraviolet reflectance have been the subject of further investigations of the preparation parameters affecting their reflectance, and of the effect of aging and exposure to conditions likely to be encountered in their applications. Techniques for monitoring the thickness of MgF(2) by reflectance measurements with ultraviolet light and by complete evaporation of weighed quantities of MgF(2) are described. It is shown that MgF(2)-protected aluminum mirrors retain their high-vacuum ultraviolet reflectance during extended exposure to air, ultraviolet irradiation, and bombardment with 1-MeV electrons and 5-MeV protons, and that such mirrors can be easily cleaned if contaminated with oil.

Further studies have been made on the preparation of LiF-overcoated aluminum mirrors with highest reflectance at wavelengths down to 1000 A. Mirrors with 73% reflectance at lambda = 1026 A have been made. The extinction coefficient k of evaporated LiF films has been measured under various conditions of film preparation. Techniques for vacuum depositing LiF films with the smallest K and Al + LiF mirrors with the highest reflectance are described. Aging of LiF-coated Al mirrors under various conditions is discussed.

No abstract