Pressure Effects of Homogeneous K Vapor in Absorption

By use of the newly developed corrosion-resistant MgO windows, the K resonance lines in absorption of a homogeneous vapor, were obtained for pressures ranging from 0.001 to 20 mm Hg. The "dispersion" equation was generally adequate to describe the observed contours. The corresponding half-breadths were linear in the density, equal as between components, but of magnitude several times that predicted by the theory of the resonance interaction. The slight asymmetry which appeared at the highest pressure was attributed to van der Waals forces. But it is pointed out that, in contradistinction to the circumstance for Hg, a quantitative verification of the inverse sixth power law is probably not possible. The infrared bands of the ${\mathrm{K}}_2$ molecule were also observed.