Isotope ratio dual-comb spectrometer

We demonstrate the use of dual-comb spectroscopy for isotope ratio measurements. We show that the analysis spectral range of a free-running near-infrared dual-comb spectrometer can be extended to the midinfrared by difference frequency generation to target specific spectral regions suitable for such measurements and especially the relative isotopic ratio delta C-13. The measurements performed present very good repeatability over several days with a standard deviation below 2 parts per thousand for a recording time of a few tens of seconds, and the results are compatible with measurements obtained using an isotope ratio mass spectrometer. Our setup also shows the possibility to target several chemical species without any major modification, which can be used to measure other isotopic ratios. Further improvements could decrease the uncertainties of the measurements, and the spectrometer could thus compete with isotope ratio spectrometers currently available on the market.

Automated summary

We demonstrate the use of dual-comb spectroscopy for isotope ratio measurements, showing that it can be extended to the mid-infrared using a difference frequency generator. The measurements performed show good repeatability and low uncertainty, with results compatible to those obtained by isotope ratio mass spectrometry.