FTS measurements of O2 collision-induced absorption in the 565–700 nm region using a high pressure gas absorption cell

Abstract

The collision-induced absorption (CIA) spectra of oxygen and dry air have been measured in the near-infrared and visible regions, covering the O2(B) band at 687 nm and double transitions in the 630 nm and 577 nm regions. A custom-design 1 m path length high-pressure cell was developed and configured to a Bruker 125HR Fourier transform spectrometer at the Jet Propulsion Laboratory. A super-luminous Laser Driven Light Source (LDLS) was also used to improve the photon flux incident upon the spectrometer. A series of spectra of pure O2 and dry air were obtained at various high pressures up to 131 bars at room temperature. For the measurement of O2–O2 CIA in the B band region, the monomer resonance absorption contribution has been subtracted from the observed spectra by simulating the O2(B) band absorption with a speed-dependent Voigt line shape profile with line mixing effects taken into account. The remaining absorption component was regarded as the CIA in the region. The integrated absorption coefficient was measured to be 3.2(6) × 10−6 cm−2/Amagat2 for the O2(B) band region, which is significantly lower than literature values. For the two double transition bands in the 630 and 577 nm regions, the integrated CIA bands from the present work were measured to be 2.50(14) and 3.26(18) × 10−4 cm−2/Amagat2, respectively. The present measurements are significantly higher than prior measurements for the 630 nm band region, while they are slightly lower than prior measurements for the 577 nm band region. For dry air, the integrated CIA bands were measured to be 0.10(2) and 0.15(2) × 10−4 cm−2/Amagat2, respectively, for the 630 and 577 nm regions, no appreciable contribution from O2–N2 pairs was observed. The results are compiled in electronic supplements.