Measurement of Carbon Dioxide Isotopes with Air-Lasing-Based Coherent Raman Spectroscopy

Isotope detection is crucial for geological research, medical diagnostics, industrial production, and environmental monitoring. Various spectroscopic techniques are continually emerging for isotopic identification and accurate measurement. Herein, coherent Raman scattering (CRS) spectroscopy is developed for the quantitative detection of carbon dioxide isotopes, in which the N₂⁺ air lasing coherently created in the interaction region is used as the probe. Benefiting from the narrow spectral width of air lasing, the Raman peaks of ¹²CO₂ and ¹³CO₂ can be well discerned, although their spectra partially overlap. The overlapped signals were proven to be the result of the coherent superposition of individual Raman signals. Based on that fact, a deconvolution algorithm was designed to retrieve the concentration ratio of the two isotopes. The relative error of the measurement is less than 6%. The CRS technique based on air lasing offers a potential approach for the quantitative characterization of molecular isotopes, especially in application scenarios of remote sensing or in situ detection.