VISCOSITY AND THERMAL-CONDUCTIVITY OF ALKALI-METAL VAPORS AT TEMPERATURES UP TO 2000-K

New experimental data were obtained on transport coefficients of alkali metals in gaseous phase at high temperatures and within the pressure range from about 10 to about 100 kPa: lithium-thermal conductivity, T = 1400-1800 K, and viscosity, T = 1600-2000 K; sodium-viscosity, T = 1100-1500 K; and cesium-viscosity, T = 900-1250 K. Viscosity of the alkali metal vapors has been measured using a stationary-technique viscometer with an annular gap. Thermal conductivity was measured by the method of the nonstationary monotonous heating. Experimental data were used as a basis for computing effective atom-atom and atom-molecule collision cross section, the values obtained from data on viscosity being in good agreement with those derived from thermal conductivity data. In the case of lithium, the atom-atom cross sections yielded by experiments are fairly consistent with the results of calculations with exact formulae of kinetic theory on the basis of quantum-mechanical potential curves for atom-atom interactions. This has enabled the authors to compile consistent tables of viscosities and thermal conductivities for lithium in a gaseous phase within the temperature range from 800 to 2500 K and pressures from 0.5 to 800 kPa, including the saturation curve.