Barbee T W, Rife J C, Hunter W R, Kowalski M P, Cruddace R G, Seely J F
Appl Opt. 1993 Sep 1;32(25):4852-4. doi: 10.1364/AO.32.004852.
The normal-incidence reflectance of a Mo/Si multilayer mirror, with peak reflectance near 130 A, was measured over a period of 20 months by using synchrotron radiation. The measured reflectances were unchanged over this period of time, and this indicates that the material layers and interfaces were stable.