A new suitor in the carbon-14 dating game. For more than 50 years, analysis of tiny amounts of radioactive 14C has served for dating organic matter. Now Pablo Cancio Pastor and colleagues at Italy’s National Institute of Optics-CNR and European Laboratory for Non-Linear Spectroscopy have developed a new method for measuring minute quantities of that isotope. Their method of saturated-absorption cavity ring-down spectroscopy (SCAR) is not as sensitive as the standard bearer for 14C sensitivity, accelerator mass spectrometry. But whereas AMS needs a dedicated facility, SCAR fits on a lab bench and is less expensive. As shown in the figure, an optical cavity filled with carbon dioxide is illuminated with an intense continuous wave laser tuned to excite a particular molecular transition in 14CO2. When the laser is turned off, the cavity intensity decays both from absorption by the 14CO2 and because light...

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