  The paper proposes a new approach to studying cathodoluminescence spectra of
substrate-free rare-gas clusters produced in supersonic jets exhausting into a
vacuum. The approach, which takes into account the fraction of the clustered
substance in the jet, is applied to quantitatively analyze integrated
intensities of the luminescence bands of the neutral and charged excimer
complexes (Rg2)* and (Rg4+)* measured for nanoclusters of three rare gases (Rg
= Ar, Kr, and Xe) with average sizes ranging from 100 to 18000 atoms per
clusters (diameters varying from 2 to 13 nm). The amount of the clustered
substance, which affects the absolute values of integrated intensity of the
bands, is shown to be proportional to the logarithm of the average size of
clusters in the jet. Analysis of normalized intensities allowed us to
spectroscopically find two ranges of average sizes of Ar, Kr, and Xe
nanoclusters which, in accordance with the electron diffraction studies, can be
assigned to quasicrystalline icosahedral and crystalline fcc structures in
clusters, as well as to find the cluster size range in which both structures
coexist. We show that in fcc clusters the luminescence of the neutral molecules
(Rg2)* comes from within the volume of the cluster, while the charged excimer
complexes (Rg4+)* emit mostly from subsurface layers.
