Аннотация:Absorption and reflection of IR radiation (500 … 6000 cm–1) by equilibrium free charge carriers are studied in free standing mesoporous Si (meso-PS) films prepared from heavily boron-doped Si wafers (Np ≈ 1020 cm–3). The experimental results are well described by a model based on the Bruggeman effective medium approximation and classical Drude theory with a correction on additional carrier scattering on the Si nanocrystal surface. The concentration of free holes in Si nanocrystals is found to be ∼1019 cm–3 and ∼1018 cm–3 for the as-prepared and naturally oxidized films, respectively.