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

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 (>10¹³ cm^-3) alkali metal vapor and it permits the measurement of the alkali metal vapor number density in the vicinity (∼10^-5cm) of cell surfaces. Using this method, we measured the number density of Rb metal vapor in the vicinity (∼10^-5cm) 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.