Global modeling of 13C 16O 2 absolute line intensities from CW-CRDS and FTS measurements in the 1.6 and 2.0 μm regions

Abstract

Line intensities of 13C 16O 2 have been measured between 5851 and 6580 cm −1 using CW-cavity ring down spectroscopy (CRDS) and in the 4700–5050 and 6050–6850 cm −1 regions using Fourier transform spectroscopy. As a result of the high sensitivity (noise equivalent absorption α min∼3×10 −10 cm −1) and high dynamics allowed by CW-CRDS, accurate line intensities of 2039 transitions ranging between 1.1×10 −28 and 1.3×10 −23 cm −1/(molecule cm −2) were measured with an average accuracy of 4%. These transitions belong to a total of 48 bands corresponding to the Δ P=9 series of transitions. Additionally, unapodized absorption spectra of 13C-enriched samples have been recorded using a high-resolution Bruker IFS125HR Fourier transform spectrometer. Spectral resolutions of 0.004 cm −1 (maximum optical path difference (MOPD)=225 cm) and 0.007 cm −1 (MOPD=128.6 cm), and pressure×path length products in the ranges 5.2–12 and 69–450 hPa×m have been used for the lower and higher energy spectral regions, respectively. Absolute line intensities have been measured in the 2001 i−00001, 3001 i−00001 ( i=1, 2, 3) and 00031−00001 bands. An excellent agreement was achieved for the line intensities of the 3001 i−00001 ( i=1, 2, 3) bands measured by both FTS and CW-CRDS. The CW-CRDS and FTS experimental intensity data together with selected intensity information from the literature have been fitted simultaneously using the effective operators approach. Two sets of effective dipole moment parameters have thus been obtained, which reproduce the observed line intensities in the 2.0 and 1.6 μm regions within experimental uncertainties.