Polarization bremsstrahlung study of the surface of xenon clusters: The pseudocrystalline state

Abstract

The half width of the polarization bremsstrahlung profile is measured as a function of the number W(N) of atoms in free clusters of xenon. The clusters are excited by electrons with energies of 0.7 and 0.3 keV, which preferentially probe the core and surface, respectively, of the clusters. It turns out the W(N) curves are entirely different for electrons with energies of 0.7 and 0.3 keV. An analysis of this difference indicates that the crystalline fcc core of clusters with sizes N ≈ 2000/8000 atoms/cluster (R ≈ 30–50 Å) is covered with a noncrystalline shell. This layer is examined in terms of the possible formation of glassy and pseudocrystalline states. For the first time a pseudocrystalline state is found in inert gas clusters. In this state the system is structurally unstable and constantly fluctuates between the liquid and solid phases.