Quantum Cascade Laser System for Simultaneous Measurements of 13CO and C18O Carbon Monoxide Isotopologues

Carbon monoxide (CO) is a key sink for atmospheric OH and thus changes in carbon monoxide concentrations have an impact on the abundance and chemistry of many other atmospheric gases. However, the CO budget is not well determined. The global sources and sinks of CO are inadequately characterized. Monitoring the isotopic composition of atmospheric carbon monoxide (13CO, C18O and CO) is one of the most promising approaches to closing the CO budget. Because these sources and sinks have both rapid temporal and sharp spatial variability, a real time isotopic monitor will be extremely beneficial. There are no existing field deployable instruments for the sensitive, real time measurement of the isotopologues of carbon monoxide. We propose to provide this capability. This proposal directly addresses the solicitations call for a field deployable CO isotope monitor under topic 29b, item (4). Recent advances in quantum cascade laser technology allow continuous wave operation near room temperature without cryogenic cooling. We propose to couple these new lasers with advanced infrared detectors and new optical designs for longer absorption path length in a compact instrument. The resulting instrument will simultaneously measure the isotopic ratios of 13CO and C18O with sufficient precision 0.4 per mil and 3 per mil, respectively, for samples with carbon monoxide mixing ratios near the typical ambient value of 200 ppb. The resulting instrument will be compact, portable and autonomous and will be sufficiently sensitive to deploy at remote field sites or even from light aircraft to assess sources and sinks of carbon monoxide throughout the world. Commercial Applications and Other Benefits: This instrument will provide atmospheric scientists with scientifically meaningful isotopic ratio measurements in real time, without preconcentration and without cryogenic cooling of either laser or detector. Other applications of this technology include air pollution monitoring, human breath analysis, and industrial process monitoring. This technology will provide a significant societal benefit through improved understanding and mitigation of global warming and global climate change