The vapor pressure of rubidium was determined in the neighborhood of 330 K from measurements of optical absorption of the resonance lines. A narrow-line source was used and a full analysis of the line profiles was done. Measurements of resonance-broadening depolarization give another check on the Rb vapor pressure in the 430-K range, assuming that theoretical cross section is correct. The results are very close to the analytic compromise previously suggested by Nesemeyanov.
A. Gallagher and E. L. Lewis, "Determination of the vapor pressure of rubidium by optical absorption," J. Opt. Soc. Am. 63, 864-869 (1973)