Thermodynamic and transport properties of cesium vapors on binodal and in its vicinity

To check the earlier proposed hypothesis on the considerable cluster effect and the ion-atom nonideality in saturated cesium vapors, a chemical model is proposed that accounts for the presence of neutral, positively, and negatively charged small-sized cluster ions and the main types of interatomic interactions. The partition sums of atoms, ions, and clusters are calculated as are the composition and pressure of cesium vapors on the binodal. It is shown that, on the saturation line, cesium vapor in the near-critical region consists mainly of atoms and a small admixture of molecules, whereas the charged component consists predominantly of $\mathrm{Cs}^-$, $\mathrm{Cs}_3^+$, and $\mathrm{Cs}_2^+$ ions whose amount is considerably lower than the amount of atoms. Interactions between charged particles and between the charged and neutral ones significantly influence the charge composition of vapors and weakly affect the equation of state and the composition of neutral component of vapors. The calculated compressibility and conductivity of the cesium vapor plasma are in good agreement with the experimental data for the near-critical isobars.