Size effect on polarization bremsstrahlung induced by electrons scattered on xenon clusters

We have measured the spectral distribution of the absolute differential cross-section of both ordinary and polarization ultra-soft X-ray bremsstrahlung for 0.7 keV electrons scattered from substrate-free nanoclusters of xenon. The clusters were produced in a supersonic gas jet that expanded adiabatically into a vacuum. The cluster density in the scattering region was determined using an original method based on absolute measurements of the intensity of the atomic and cluster emission in the vacuum ultraviolet and ultra-soft X-ray spectral regions. The bremsstrahlung from scattering of electrons by clusters had a polarization component that dominated the differential cross-section. For the first time, the effect of cluster size on the formation of polarization bremsstrahlung was found for xenon.