FT-IR spectra of 17O-enriched CO2 in the ν3 region: High accuracy frequency calibration and spectroscopic constants for 16O12C17O, 17O12C17O, and 17O12C18O

Abstract

We report new Fourier transform infrared (FT-IR) spectroscopy measurements of the 17O-enriched isotopologues of CO2 in the ν3 region (2200–2450cm−1, 65–75THz) with absolute calibration accuracies better than 3×10−6cm−1 (∼100kHz) for strong, isolated transitions. Spectra were obtained using the JPL Bruker IFS-125HR Fourier Transform Spectrometer (JPL-FTS). The JPL-FTS performance was achieved by vigorously maintaining the optical alignment, regularly monitoring its modulation efficiency while minimizing phase errors to deliver absolute frequency calibration and line position accuracies comparable to typical sub-millimeter/THz spectroscopy. Fits of the 00011←00001 fundamental bands for 16O12C17O (627), 17O12C17O (727), and 17O12C18O (728) were obtained with RMS residual values of 2.9×10−6cm−1 for all three isotopologues. These results provide a complete and accurate set of transition frequencies required for remote sensing of planetary atmospheres, especially Venus and Mars, and represent a new level of Doppler measurement accuracies.