B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine, 47 Nauki Ave., Kharkiv 61103, Ukraine
Received September 13, 2019, published online December 27, 2019
The paper proposes a new approach to quantitatively analyzing cathodoluminescence spectra of substrate-free rare-gas clusters produced in a supersonic jet exhausting into a vacuum. The approach, which takes into account the level of substance clustering in the jet, is applied to analyze 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 the average size ranging from 100 to 18000 atoms per clusters (diameters varying from 2 to 13 nm). The concentration of the clustered substance, which affects the absolute values of the integrated intensity of the spectral bands, is shown to be proportional to the logarithm of the average size of the clusters in the jet. Analysis of the normalized intensities allowed us to use our cathodoluminescence spectra to establish two ranges of average nanocluster size which, according to the electron diffraction studies, can be identified as those corresponding to the quasicrystalline icosahedral and crystalline fcc structures in clusters of argon, krypton, and xenon, as well as to find an intermediate area in which both structures coexist. It is shown 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 a subsurface layer.