Detection of trace concentrations of H2 in air by coherent active Raman spectroscopy

The method of coherent active Raman spectroscopy was used in express analysis of molecular hydrogen in a mixture with air at a total pressure of 1 atm. The measurements were carried out using an automated pulsed spectrometer, which included a YAG:Nd³⁺ laser with an amplifier, a dye laser, and a DFS-24 spectrograph. The width of the instrumental function was 0.15 cm^–1, the time needed to record the spectrum was 20 sec, and the sensitivity limit was 0.2 ppm of H₂. A study was made of the possibility of further improvement of the spectrometer sensitivity in the analysis of gas impurities.