Mid-infrared trace detection with parts-per-quadrillion quantitation accuracy: Expanding frontiers of radiocarbon sensing

Journal Article · 21 March 2024 · Proceedings of the National Academy of Sciences of the United States of America

DOI: https://doi.org/10.1073/pnas.2314441121 · OSTI ID:2326247

Jiang, Jun  ^[1]; McCartt, A. Daniel  ^[1]

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1. Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)

Detection sensitivity is a critical characteristic to consider during selection of spectroscopic techniques. However, high sensitivity alone is insufficient for spectroscopic measurements in spectrally congested regions. Two-color cavity ringdown spectroscopy (2C-CRDS), based on intra-cavity pump–probe detection, simultaneously achieves high detection sensitivity and selectivity. This combination enables mid-infrared detection of radiocarbon dioxide (¹⁴CO₂) molecules in room-temperature CO₂ samples, with 1.4 parts-per-quadrillion (ppq, 10^-15) sensitivity (average measurement precision) and 4.6-ppq quantitation accuracy (average calibrated measurement error for 21 samples from four separate trials) demonstrated on samples with ¹⁴C/C up to ~1.5 x natural abundance (~1,800 ppq). These highly reproducible measurements, which are the most sensitive and quantitatively accurate in the mid-infrared, are accomplished despite the presence of orders-of-magnitude stronger, one-photon signals from other CO₂ isotopologues. This is a major achievement in laser spectroscopy. A room-temperature-operated, compact, and low-cost 2C-CRDS sensor for ¹⁴CO₂ benefits a wide range of scientific fields that utilize ¹⁴C for dating and isotope tracing, most notably atmospheric ¹⁴CO₂ monitoring to track CO₂ emissions from fossil fuels. The 2C-CRDS technique significantly enhances the general utility of high-resolution mid-infrared detection for analytical measurements and fundamental chemical dynamics studies.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA), Office of Defense Nuclear Nonproliferation
• Grant/Contract Number: AC52-07NA27344; NA; DE440 AC52-07NA27344
• OSTI ID: 2326247
• Alternate ID(s): OSTI ID: 2475265
• Report Number(s): LLNL-JRNL-850018; 1075894
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America, Vol. 121, Issue 15; ISSN 0027-8424
• Publisher: National Academy of SciencesCopyright Statement
• Country of Publication: United States
• Language: English