Reflecting properties of narrowband Si/Al/Sc multilayer mirrors at 58.4  nm

This study considers the reflective characteristics of three-component Si/Al/Sc multilayer mirrors with a M o S i 2 protective cap layer as candidates for telescopes for observation of the solar corona in the He I ( λ = 58.4 n m ) spectral line. At 58.4 nm, a peak reflectance of 32% and a spectral width at a half-maximum intensity of Δ λ = 5.4 n m are obtained. The temporal stability of the reflectance at λ = 58.4 n m for Si/Al/Sc samples with a 6 nm thick M o S i 2 cap layer is investigated during storage in air for 20 months.