Interpretation of the visible and near-infrared absorption spectra of compressed oxygen as collision-induced electronic transitions

Abstract

The intensity profiles of some of the broad continuous absorption bands of oxygen in the near-infrared and visible regions were measured in the compressed gas over a range of pressures and temperatures. Three single electronic transitions (12 600, 10 600, 07620 Å) and three double transitions (6290, 5770, 4770 Å) were studied in detail. The asymmetry of the band profiles is shown to arise from a Boltzmann relation between the intensity distributions in the high and low frequency wings when the band origin is properly chosen. By assuming an appropriate rotational structure and broadening each rotational transition by a Boltzmann-modified dispersion curve the profiles of the bands could be reproduced with only minor discrepancies. These criteria, along with the well-known quadratic density dependence of the intensity, show that the bands are properly interpreted as collision-induced electronic transitions. The large width of the translational broadening functions required in the analysis indicates that the induction must be predominantly due to overlap interaction. No specific effects of (O2)2 complexes are identifiable in the spectra.