Optical determination of alkali metal vapor number density in the vicinity (∼10^-5 cm ) of cell surfaces

Abstract

We describe a method for determining the number density of the alkali metal vapor by use of an evanescent wave in a single total internal reflection. The method is simple to use, and it has the following useful features: It is most suitable for determining the number density of dense $(>{10}^{13} {\mathrm{cm}}^{-3})$ alkali metal vapor and it permits the measurement of the alkali metal vapor number density in the vicinity $(\sim {10}^{-5} \mathrm{cm})$ of cell surfaces. Using this method, we measured the number density of Rb metal vapor in the vicinity $(\sim {10}^{-5} \mathrm{cm})$ of the cell wall in cells that contain only Rb metal and no buffer gas; we found that there is no systematic difference between the Rb number density near the surface and that in the bulk.