A. B. Vakhtin and D. S. Bomse, Optical Isotope Analyzer for Subsurface Gases.
We will describe A Raman spectrometer for field measurement of isotope ratios of subsurface gases including nitrogen, oxygen and carbon dioxide. Raman scattering makes it possible to measure isotope the isotope ratios of all three gases simultaneously using a single instrument. The approach is particularly useful for soil gases where carbon dioxide concentrations are much higher than in the atmosphere. The following figure shows raw data from air (low CO2 concentration) and identifies the minor isotope contributions in O2 and N2.