Self- and air-broadened cross sections of ethane (C2H6) determined by frequency-stabilized cavity ring-down spectroscopy near 1.68 µm

- We measured spectra of pure and air-broadened ethane in the 1.7 μm region.
- Measured cross sections were substantially different than literature values.
- Relative uncertainties of measured cross sections were less than 1 %.
- These results can be used to quantify ethane/methane ratios for source apportionment.

The absorption spectrum of ethane was measured by frequency-stabilized cavity ring-down spectroscopy over the wave number range 5950-5967 cm−1. Spectra are reported for both pure ethane acquired at pressures near 3 Pa and mixtures of ethane in air at pressures ranging from 666 Pa to 101.3 kPa. Absorption cross sections are reported with a spectrum sampling period of 109 MHz and frequency resolution of 200 kHz. Atmospheric pressure cross sections agree fairly well with existing cross sections determined by FTS in nitrogen, but there are significant variations in cross sections at lower pressures. Source identification of fugitive methane emissions using spectroscopic measurements of the atmospheric ethane-to-methane ratio is also discussed.