  We measured spectral distribution of absolute differential cross section of
both ordinary and polarization bremsstrahlung for 0.3-1.0 keV electrons
scattered on atoms and substrate-free nanoclusters of xenon. Clusters were
produced in a supersonic gas jet expanding adiabatically into a vacuum. An
original method based on absolute measurements of intensity of the atom and
cluster emission in the VUV and USX spectral regions was used to determine the
cluster density in the scattering area. The bremsstrahlung arising from
scattering on clusters had a polarization component which dominated the
differential cross section. For the first time cluster size effect on the
formation of the polarization bremsstrahlung was found for xenon.
