Radiocarbon's natural production, radiative decay, and isotopic rarity make
it a unique tool to probe carbonaceous systems in the life and earth sciences.
However, the difficulty of current radiocarbon (14C) detection methods
limits scientific adoption. Here, two-color cavity ring-down spectroscopy
detects 14CO2β in room-temperature samples with an accuracy of 8% of
the natural abundance in 3 minutes. The intra-cavity pump-probe measurement
uses two cavity-enhanced lasers to cancel out cavity ring-down rate
fluctuations and strong one-photon absorption interference (>10,000 1/s) from
hot-band transitions of CO2β isotopologues. Selective, room-temperature
detection of small 14CO2β absorption signals (<1 1/s) reduces the
technical and operational burdens for cavity-enhanced measurements of
radiocarbon, which can benefit a wide range of applications like biomedical
research and field-detection of combusted fossil fuels.Comment: 4 main figures, 2 supplementary figure