Parameterized model to approximate theoretical collision-induced absorption band shapes for O2-O2 and O2-N2

Abstract

Collision-induced absorption from vibronic transitions of O2-O2 and O2-N2 collision complexes is an important contributor to light-matter interaction in the atmosphere with relevance to radiative heat transfer and remote sensing. Despite in-depth studies involving quantum calculations of this effect, comparisons between experiment and theory would benefit from less computationally burdensome calculations that closely approximate the temperature dependence of the theoretical band shape and intensity. Accordingly, we present a parameterized representation of recent quantum calculations for collision-induced absorption by O2-O2 and O2-N2 about the 1.27 μm monomer band of O2. This approach leverages the theoretical decomposition of the spectra into exchange and spin-orbit contributions, with each component having a distinct temperature-dependent band shape. Composite spectra are approximated as a linear combination of the theoretical profiles with seven adjustable parameters that scale the component intensities and their dependences on temperature. We demonstrate that this empirical representation can accurately simulate the theoretical calculations, and we present a global fit of the model to previously reported collision-induced absorption spectra (O2-O2, O2-N2, and O2-air) measured by cavity ring-down spectroscopy over the temperature range 271 K–332 K.