XANES of high-pressure Kr clusters in Be and Si

We report on the experimental investigation of high-pressure Kr clusters in Be and Si single crystals by x-ray absorption near-edge spectroscopy. The samples, obtained by ion implantation, were investigated for several temperatures in the range 83--670 K. We show that the near-edge structure of the absorption spectra is sufficient to obtain valuable quantitative information concerning the contracted lattice parameter of the solid rare gas agglomerates, depending on the overpressure exerted on the clusters by the host matrix. Our data compare to the extended x-ray absorption fine structure (EXAFS) experimental spectra on solid Kr at 4.2 K, and at 300 K under high pressure. Furthermore, in order to check the consistency of our experimental data with EXAFS results taken from the literature, we performed theoretical simulations using the FEFF6 code. These calculations showed good agreement with both sets of data and confirmed our experimental conclusions, permitting the evaluation of the lattice contraction, average coordination, and size of the cluster ensemble.