ROOM TEMPERATURE OPTICAL DETECTION OF ¹⁴CO₂ AT PARTS-PER-QUADRILLION LEVEL ACCURACY WITH TWO-COLOR CAVITY RINGDOWN SPECTROSCOPY

Jiang, Jun

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https://hdl.handle.net/2142/122347 Copy

Description

Title

ROOM TEMPERATURE OPTICAL DETECTION OF ¹⁴CO₂ AT PARTS-PER-QUADRILLION LEVEL ACCURACY WITH TWO-COLOR CAVITY RINGDOWN SPECTROSCOPY

Author(s)

Jiang, Jun

Contributor(s)

McCartt, A. Daniel

Issue Date

2023-06-20

Keyword(s)

Spectroscopy as an analytical tool

Abstract

In this talk, we report room-temperature optical detection of radiocarbon dioxide (¹⁴CO₂) with better than 10 parts-per-quadrillion (10¹⁵, ppq) (¹⁴C/C) measurement accuracy with the two-color cavity ringdown (2C-CRD) technique. The current sub-10-ppq measurement accuracy of ¹⁴CO₂ is 10X better than our previous work [McCartt, A. D., & Jiang, J. (2022). ACS Sensors, 7(11), 3258-3264], which demonstrated the first-ever room temperature detection of ¹⁴CO₂ at concentrations below the natural abundance (∼1200 ppq ¹⁴C/C). This significantly enhanced measurement capability of our 2C-CRD technique, achieved with under 2 minutes of averaging, is made possible by a combination of 30X improvement in the signal-to-noise ratio in our detection system and nearly 10X reduction in the magnitude of the collisionally-induced background 2C signal. As in our previous work, cavity-enhanced pump and probe laser beams are used to excite a pair of ν₃=1-0 and ν₃=2-1 rovibrational transition of ¹⁴CO₂. With the pump radiation switched off during every other probe ringdown events, the net 2C signals from the difference between the pump-on and pump-off decay rates is immune to drifts of the CRD rates and spectral overlaps from one-photon molecular transitions. The 10-ppq level detection capability of our 2C-CRD technique has been reproducibly demonstrated with several rounds of measurements of combusted ¹⁴C standard samples (with close to contemporary ¹⁴C concentrations) and low ¹⁴C content biofuel samples (10-80 ppq ¹⁴C/C). Room temperature optical detection of ¹⁴CO₂ at our demonstrated sensitivity and accuracy is not possible with other existing one-photon detection methods, because of severe spectral overlap between the very weak ¹⁴CO₂ ν₃-band transitions (∼4/s RD rate at natural abundance) and the strong hot-band transitions of other CO₂ isotopologues (∼10000/s). In addition to its use for ultra-trace analysis, our cavity-enhanced 2C technique is well-suited for rovibrational-state-resolved measurements in chemical dynamics and high-resolution spectroscopic studies, which we will discuss at the end of the talk.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

Text

Language

eng

Handle URL

https://hdl.handle.net/2142/122347

DOI

https://doi.org/10.15278/isms.2023.6891

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