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Title:Optically-switched Dual-wavelength Cavity Ring-down Spectrometer For High-precision Isotopic Ratio Measurements Of Methane δd And 13c In The Near-infrared
Author(s):Chen, TzuLing
Contributor(s):Okumura, Mitchio; SHEN, LINHAN; Bui, THINH; MIRI, ROBIN; Ober, Douglas
Subject(s):Spectroscopy as an analytical tool
Abstract:We report a spectrometer employing optically-switched dual-wavelength cavity ring-down spectroscopy (OSDW-CRDS) for high-precision measurements of methane isotopic ratios. A wave-guide optical switch rapidly alternated between two wavelengths to detect absorption by two isotopologues using near-infrared CRDS. This approach alleviated common-mode noise that originated primarily from temperature and frequency fluctuations. We demonstrated the measurement of $\delta$D in natural abundance methane to a precision of 0.23~\%, despite the lack of active temperature or frequency stabilization of the cavity. The ability of alternating OSDW-CRDS in improving isotope precision were measured by Allan deviation as varying switching time intervals (0.1~Hz$\sim$10~Hz) and the use of frequency-stabilizing cavity length. This system can be extended to a wide variety of applications such as isotope analysis of other species, kinetic isotope effects, {\it ortho-para} ratio measurements, and isomer abundance measurements. Furthermore, our technique can be extended to multiple isotopic analysis through the use of multi-port optical switches.
Issue Date:2021-06-24
Publisher:International Symposium on Molecular Spectroscopy
Genre:Conference Paper / Presentation
Date Available in IDEALS:2021-09-24

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