High Sensitivity Isotopic Gas Concentration-Ratio Measurement using Isotopic Gas Laser Oscillation

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For high sensitivity measurement of isotopic concentration-ratio of trace-level gas mixture, particularly including carbon dioxide isotopes, we tested a ^<12>CO_2-^<13>CO_2 composite laser system containing intracavity absorption cells. Sensitivity enhancement obtainable by the intracavity absorption cell configuration was examined theoretically and found to be around 100.To estimate the ultimate sensitivity of the present system, we tried to detect ^<13>CO_2 and ^<12>CO_2 in atmospheric air and artificial breath.^<13>CO_2 inclouded in atmospheric air and in the artificial were detected by a ^<13>CO_2 laser having the intracavity absorption cell, minimum detectable concentration by the present system was estimated to be 20ppb.