Line intensities of CO near 1560 nm measured with absorption and dispersion spectroscopy

TL;DR

This study demonstrates high-precision measurement of CO line intensities near 1560 nm using combined absorption and dispersion spectroscopy, enabling SI-traceable molecular density assessments.

Contribution

It introduces simultaneous absorption and dispersion measurements of CO lines with agreement within 0.1%, advancing precise, traceable gas quantification methods.

Findings

Line intensities agree within 0.1% between methods

Nine CO lines measured in the R branch of v=3-0 band

Feasibility of SI-traceable molecular density measurements demonstrated

Abstract

High-precision line intensities are of great value in various applications, such as greenhouse gas metrology, planetary atmospheric analysis, and trace gas detection. Here we report simultaneous measurements of cavity-enhanced absorption and dispersion spectroscopy of the prototype molecule $^{12}$C$^{16}$O using the same optical resonant cavity. Nine lines were measured in the R branch of the $v=3-0$ band. The absorption and dispersion spectra were fitted separately with speed-dependent Voigt profiles, and the line intensities obtained by the two methods agree within the experimental uncertainty of about 1\textperthousand. The results demonstrate the feasibility of SI-traceable molecular density measurements based on laser spectroscopy.