Measurement of Rubidium Number Density Under Optically Thick Conditions

摘要

A measurement of rubidium number density under optically thick conditions has been demonstrated by measuring the wings of the D1 absorption spectra using a laser with a 0.16 nm (75 GHz) fine tuning range. This technique can measure the absolute concentration in rubidium under conditions where the absorption coefficient and path length product yield conditions where the central region of the line is opaque. The laser was tuned to a region sufficiently far into the short wavelength wing of the absorption where transmission through the cell was possible. The laser was then scanned through the central opaque region of the line to the adjacent long wavelength wing. The wavelength of the scan was calibrated by using a 1.5 GHz etalon and a cell containing only naturally occurring rubidium as a frequency reference. The measured absorption spectra for various cell conditions of temperature and pressure were then fit to a pressure broadened Voigt profile thereby allowing the determination of the rubidium number density.