  We propose a new approach to analysis of cathodoluminescence spectra of
substrate-free nanoclusters of argon produced in a supersonic jet expanding
into a vacuum. It is employed to analyze intensities of the luminescence bands
of neutral and charged excimer complexes (Ar2)* and (Ar4+)* measured for
clusters with an average size of 500 to 8900 atoms per cluster and diameters
ranging from 32 to 87 {\AA}. Concentration of the jet substance condensed into
clusters, which determines the absolute values of the integrated band
intensities, is shown to be proportional to the logarithm of the average
cluster size. Analysis of reduced intensities of the (Ar2)* and (Ar4+)* bands
in the spectra of crystalline clusters with an fcc structure allows us to
conclude that emission of the neutral molecules (Ar2)* comes from within the
whole volume of the cluster, while the charged complexes (Ar4+)* radiate from
its near-surface layers. We find the cluster size range in which the jet is
dominated by quasicrystalline clusters with an icosahedral structure and
demonstrate that the transition from icosahedral to fcc clusters occurs when
the average cluster size is N = 1400+-400 atoms per cluster.
