Adsorption and Condensation of Water on Mirror and Lens Surfaces
NAVAL RESEARCH LAB WASHINGTON DC
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This is a report of a literature search on adsorption and condensation of water on mirror and lens surfaces. Adsorbed water films on clean surfaces are generally 3.0 nm thick and can be ignored when considering absorption losses. When the surfaces are exposed to ambient conditions, various aerosols of dusts and hygroscopic particles are deposited on the surfaces which give rise to small losses by scattering of the incident radiation. In the case of hygroscopic particles the problem can be especially troublesome because here the scattering magnitude is a function of the relative humidity. For a given aerosol deposit an optical system containing a 6 mirror train will have a cumulative reflectivity decrease of about 7 as the relative humidity varies from 60 to 80.