Room-temperature quantification of $^{14}$CO$_{2}$ below the natural abundance with two-color cavity ring-down spectroscopy

TL;DR

This paper introduces a novel two-color cavity ring-down spectroscopy method capable of detecting $^{14}$CO$_{2}$ at natural abundance levels in room-temperature samples within minutes, significantly simplifying radiocarbon detection.

Contribution

The study demonstrates room-temperature, high-accuracy detection of $^{14}$CO$_{2}$ using a two-color cavity ring-down spectroscopy technique that cancels out fluctuations and interference, enabling practical radiocarbon measurements.

Findings

Achieved detection accuracy at one-tenth natural abundance.

Detection time reduced to 3 minutes.

Method suppresses interference from hot-band CO$_{2}$ transitions.

Abstract

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 ($^{14}$C) detection methods limits scientific adoption. Here, two-color cavity ring-down spectroscopy detects $^{14}$CO$_{2}$ in room-temperature samples with an accuracy of one-tenth 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 CO$_{2}$ isotopologues. Selective, room-temperature detection of small $^{14}$CO$_{2}$ 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.