Density of Ar Metastable Atoms on the Discharge Tube Wall Measured by Evanescent Laser Spectroscopy

Abstract

In order to measure the density of excited atoms in the metastable state on a discharge tube wall, evanescent wave spectroscopy is applied to a pure Ar discharge. In the experiments, the evanescent laser wave interacts with the Ar metastable atoms. The detection of the evanescent-laser-induced fluorescence and the laser-induced evanescent-mode fluorescence indicates the existence of metastable atoms in the vicinity of the wall within one wavelength of the laser. The absolute value of density is obtained in comparison with the signal for Rb atoms in the same system. The reflectance of metastable atoms at the wall is also estimated.