Absorption and Reactions of 1,1-dimethyl-hydrazine on the Surface of Magnesium Fluoride Coating

The absorption and chemical reactions of 1,1-dimethyl-hydrazine(C2H8N2) on the surface of magnesium fluoride(MgF2) coating was studied. The coating surface is firstly contaminated by liquid or gaseous C2H8N2 , and then it is placed into a vacuum environment for a long period. Contrasting the infrared absorption spectra, X-ray photoelectron energy spectra and diffusive reflectivity of MgF2 coating surfaces before and after experiment, it may be learned that the absorption and chemical reactions occur at the surface. The experimental results show that the molecules of a liquid film of C2H8N2 over MgF2 coating surface take about two hours to desorb adequately in a vacuum environment, after the adequate desorption, there only exists a single chemical absorption layer over the coating surface, with a mass density of about 27 ng/cm2. The diffusive reflectivity of MgF2 coating surface decreases about 10%-15% after the contamination of liquid C2H8N2. For MgF2 coating surfaces immersed in C2H8N2 vapor at the pressure of 3 kPa for ten minutes, there are neither changes in their atomic constitution and diffusive reflectivity， nor characteristic peaks of C2H8N2 appear in their infrared absorption spectrum.