Singularity in the LEIS spectrum of metal nanoclusters

The asymmetry of lines has been observed in the spectra of the inelastic scattering of low-energy ions interacting with nanoclusters of $d$ metals. It is attributed to the mechanism of exciting $e{-}h$ pairs with low energies and high momenta (infrared catastrophe). Analysis of the asymmetry of x-ray photoelectron spectra and spectra of low-energy scattered ions shows that the Anderson singularity indices $\alpha$ associated with the electron states on the surface and in bulk have different behaviors as functions of the nanocluster size. The results cannot be explained in the framework of the available concepts of the redistribution of these contributions with decreasing of the nanocluster size.