A Novel, In-Situ Method for Absolute Spectral Sensitivity Calibration of a Spectrometer-Detector System by Using Laser-Induced-Fluorescence Spectroscopy

We propose a calibration method for the absolute sensitivity of a spectrometer-detector system by applying laser-induced-fluorescence spectroscopy (LIFS) to a discharge plasma. The object of our experiment is to determine the absolute line intensity emitted from the plasma: For a spectral line, the absolute lower-level population on the tube axis before the laser excitation is determined by the self-absorption method combined with LIFS, which determines its spatial distribution, while the upper-level population is negligible compared with the lower-level population. When intense laser-excitation (broad-line excitation) saturates the upper-level population, its absolute value is given from the lower-level one as determined above. By combining the line intensity and the detector output, we determine the absolute sensitivity of the detection system. The above procedure has been applied to He(I) 504.8-nm and Ne(I) 616.4-nm transitions. The results are compared with our previous determination against a tungsten ribbon lamp.