The research on rare earths conducted by the current team addresses in this proceeding the transmittance measurement of
Ce films. Several thin films of Ce were deposited by evaporation in ultra high vacuum (UHV) conditions and their
transmittance was measured in situ in the 6-1,200 eV spectral range. Ce films were deposited onto grids coated with a
thin, C support film. Transmittance measurements were used to obtain the extinction coefficient of Ce films at each
individual photon energy investigated. Literature data for Ce films had been restricted to some parts of the current range,
with various experimental data at the strong N edge, a single set of data at the M edge, and no data at the O edge. The
energy range here investigated provides data encompassing M, N, and O edges of Ce, and this data set is extended
towards smaller energies with experimental data and towards larger energies with semi-empirical data and calculations.
Ce, as has been measured with other lanthanides, has a low-absorption band right below the O edge, with lowest
absorption at 16.1 eV. This makes Ce a promising material for filters and multilayer coatings in this spectral range, in
which few developments have been performed due to the lack of low absorption materials. The f1 sum-rule was applied
to the extinction coefficient data in the whole spectrum that included the current data along with those of the literature,
resulting in a value close to predictions, which shows the consistency of the current data.