Fig. (9) Be mirror reflectance at the indicated wavelengths. 1 – reflectance drop due to 1350 eV ion bombardment; 2- reflectance recovery after long-term exposures to 60 eV ions; 3 – partial reflectance recovery after vacuum annealing for 2 hours at 200°C . X1, X2, and X3 indicate the states of experiment when XPS measurements were provided (see Fig. 10).