Broad full widths of half maxima (dampings) are observed from the low-frequency Raman spectra of hydrothermally prepared SnO2 nanocrystal congeries. No matrix exists between these nanocrystals and the complex-frequency model is thus unable to explain the damping in the low-frequency Raman peaks. An alternative model in which damping is induced by the interaction between confined surface acoustic vibrations and localized electrons near the nanocrystal surface is proposed to explain the phenomenon. This model which suggests that damping is proportional to d−3/2, where d is the average diameter of nanocrystals, is corroborated by our experimental results.

The experimental measurement of electron-impact K-shell ionization cross sections of Cu and Co elements within the energy region 8-25 keV was reported. The influence of a substrate of thin targets on ionization cross sections has been corrected by a method based upon a bipartition model of electron transport ͓Z. M. Luo, Phys. Rev. B 32, 812 ͑1985͒; 32, 824 ͑1985͔͒. The measured cross sections are in good agreement with existing data and are well reproduced by the empirical formula of Green and Cosslett ͓Proc. Phys. Soc. London 78, 1206