The atmospheric continuum in the “terahertz gap” region (15–700 cm−1): Review of experiments at SOLEIL synchrotron and modeling

T.A. Odintsova (1) , A.O. Koroleva (1) , A.A. Simonova (2) , A. Campargue (3) , M.Yu. Tretyakov (1)

1 Institute of Applied Physics of RAS
2 IAO - V.E. Zuev Institute of Atmospheric Optics
3 LIPhy - Laboratoire Interdisciplinaire de Physique [Saint Martin d’Hères]

The results of our recent water vapor related continuum studies in the range of the "terahertz gap" at the AILES beam line of the SOLEIL synchrotron using Fourier transform spectrometer are reviewed and summarized. The continuum of pure water vapor and its mixture with N 2 , O 2 and dry air were investigated in the 15-700 cm-1 range in conditions close to atmospheric. Analysis of the frequency and temperature dependence of the selfcontinuum revealed a significant contribution of stable water dimer to the observed absorption, which is not taken into account by the MT_CKD semi-empirical model of the continuum, widely used for atmospheric applications. We propose a physically based approach for the continuum modeling, which accounts explicitly for the contribution of dimers and far wings of monomer resonance lines. We applied the suggested approach for the water vapor self-continuum modeling in the H 2 O rotational band and sustained it by comparison to the SOLEIL data. The frequency dependence of the relative contributions of far wings, stable and metastable dimers to the self-continuum is evaluated. Prospects for further developments of the atmospheric continuum modeling are given.

Mots clés: SOLEIL synchrotron; atmospheric continuum; THz gap; dimer; far wings

Domaines: Physique [physics]

T.A. Odintsova, A.O. Koroleva, A.A. Simonova, A. Campargue, M.Yu. Tretyakov. The atmospheric continuum in the “terahertz gap” region (15–700 cm−1): Review of experiments at SOLEIL synchrotron and modeling. Journal of Molecular Spectroscopy, 2022, 386, pp.111603. ⟨10.1016/j.jms.2022.111603⟩. ⟨hal-03865589⟩