Raman spectroscopic studies of isotopic diatomic molecules and a technique for measuring stable isotope ratios using Raman scattering

A method for measuring stable isotope ratios using Raman scattering was developed which consists of simultaneously counting photons scattered out of a high-intensity laser beam by different isotopically-substituted molecules. As a result of the Raman isotope effect, isolation of photons from different isotopic species is readily accomplished by using monochromators. Extrapolation of measured count rates to those obtainable by improving laser and monochromator systems indicates that highly-accurate isotope ratio measurements ( or = 0.1% precision) can be made using Raman scattering in less than one-tenth the time required for the same measurement using conventional mass spectrometry. A Raman spectrometer was assembled which can obtain much higher resolution (approximately 0.1/cm) than a conventional spectrometer and allows work with signal levels heretofore impractical ( 0.1 counts/sec). Using this spectrometer a number of studies of isotopic diatomic molecules were made.