Vapor pressure of rubidium between 250 and 298 K determined by combined fluorescence and absorption measurements

Abstract

In the temperature range 250–298 K the saturated vapor pressure of rubidium in a glass cell was determined. The rubidium ground-state atoms of the naturally abundant isotope 85Rb were excited with a narrow-band dye-laser beam, and the resulting (relative) fluorescence was measured as a function of the temperature of the cell. At a fixed temperature of 296.6 K the absorption of the laser beam at the top of the absorption profile was measured. When the calculated cross section for photon absorption was used, the absolute density was determined and related to the corresponding fluorescence signal. The measurements permit the determination of the heat of vaporization, 82.3 ± 0.3 kJ mol−1.