Abstract: The methods and apparatus described may be used for the discrimination of two closely spaced spectral lines. In certain embodiments the methods and apparatus may be used for the detection of isotopes and isotopic ratios by Raman spectroscopy. In certain embodiments the conversion of a labeled substrate to a labeled product may be detected. In particular embodiments the conversion of a 13C labeled substrate to a 13C labeled product may be detected. In other embodiment the conversion of 13C urea to 13CO2 is detected. Embodiments described include the diagnostic determination of 13CO2/12CO2 ratio in a test sample.

Abstract: The methods and apparatus described may be used for the discrimination of two closely spaced spectral lines. In certain embodiments the methods and apparatus may be used for the detection of isotopes and isotopic ratios by Raman spectroscopy. In certain embodiments the conversion of a labeled substrate to a labeled product may be detected. In particular embodiments the conversion of a 13C labeled substrate to a 13C labeled product may be detected. In other embodiment the conversion of 13C urea to 13CO2 is detected. Embodiments described include the diagnostic determination of 13CO2/12CO2 ratio in a test sample.

Abstract: An improved Raman spectrometer is provided, having, in a preferred embodiment, a light source comprising an injection-locked laser diode array, a multipass cell to multiply the intensity of the light source, a dynamic gas sample focusing system, and an atomic vapor filter to remove the Rayleigh scattered light. The laser diode arrays are tuned to match an absorption band of the atomic vapor filter. The Raman scattered light passes virtually unattenuated through the filter to be recorded by a Fourier transform spectrometer or other spectrometer. This invention permits higher sensitivity and resolution than prior art Raman spectrometers, in particular permitting identification and measurement of Raman emissions that occur at low wave numbers. The light source of this invention can also be used in conjunction with optical notch filters and photodetectors to permit detection and measurement of preselected species in a sample.