We present in this paper a study of the population decay of resonantly excited energy levels in ions of Rb+(5s[1/2]1, 4d3P1), Cs+(5d[1/2]1, 6s[3/2]1, 6s[1/2]1) and in atoms of He (21P1), Ne (3 s1P1), made using their VUV spectra in a decomposing plasma in the mixtures of Ne-Cs and He-Rb. The investigations carried out enabled us to derive the rates of helium and neon atomic ion conversion into the molecular ones, resulting from three-particle collisions in Ne-Cs and He-Rb mixtures. The rates are k(Ne)=0.62(±0.2)×10–31 сm6/s, k(He)=3.18(±0.8)×10–31 сm6/s, correspondingly. We also have analyzed the role of nonresonance charge exchange in these mixtures. The total rate constant of the charge exchange in the He-Rb mixture has been estimated to be δ = 3.88 ( ± 0.9)×10–10 сm3/s. For the Ne-Cs mixture we have obtained the value of the total rate constant of the energy transfer from the particles in metastable states to cesium ions in the nearest resonantly excited states through interaction with low energy electrons (αe = 4.9 ( ± 1.6)×10–7 сm3/s). The value of radiation recombination of Cs++ was obtained to be equal to αe++ = 1.45(±0.3) 10-8 cm3s-1.