Radiocarbon measurements with mid-infrared SCAR spectroscopy

Since its first invention and demonstration [1], saturated-absorption cavity ring-down spectroscopy (SCAR) of CO2 gas samples at 4.5 µm wavelength has been approaching accelerator mass spectrometry (AMS) precision in radiocarbon measurements. The first intercomparison between SCAR and AMS measurements was performed with modern (fermentation of brown cane sugar) and fossil (high-purity industrial gas cylinder) carbon dioxide samples [2]. These successful results have triggered further optimization of the data fitting procedure [3] and significant upgrades of the SCAR experimental apparatus, leading to an improved performance of the spectrometer in terms of precision and repeatability [4]. Recently, an independent research group has reproduced SCAR spectroscopy, assessing the working limits of this techniques in terms of saturation parameter with measurements on a different molecular species [5].