Two collision-induced absorption features of oxygen have been investigated by means of the laser-based cavity ring-down technique at pressures between 0 and 1000 hPa and at temperatures in the range 184–294 K. Peak cross sections, resonance widths and integrated cross sections, as well as spectral profiles, have been determined for the broad O2O2–O2O2 resonances centered at 477 and 577 nm. Results are compared with previous measurements to establish an updated temperature dependence for the cross sections of both resonances, yielding integrated cross sections, that exhibit a minimum near 200 K and that increase in a near-linear fashion in the atmospherically relevant range of 200–300 K. A significant increase in the widths of the resonance profiles upon temperature increase is firmly established. Parameters and temperature-dependent trends for the shape and strengths of the resonances are produced, that can be implemented in cloud retrieval in atmospheric Earth observation.
Papers with the following subject areas are suitable for publication in the Journal of Quantitative Spectroscopy and Radiative Transfer:
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he collision-induced absorption of oxygen in the 540–650-nm wavelength region has been measured at a pressure range from 0 to 730 Torr at T = 294 K. Pressure-dependent cross sections of the 𝑋 3∑+𝑔 + 𝑋 3∑+𝑔 → a 1Δg(v = 0) + a 1Δg(v = 1) and 𝑋 3∑+𝑔 + 𝑋 3∑+𝑔 → a 1Δg(v = 0) + a 1Δg(v = 0) transitions have been determined by means of cavity-ringdown spectroscopy. Contributions of the overlapping γ and δ bands of O2 have been evaded, and Rayleigh extinction has been taken into account.
