CO₂-CO₂ and CO₂-Ar continua at millimeter wavelengths

Broadband spectra of the continuum absorption in pure CO2 gas and its mixture with Ar are studied at room temperature using a resonator spectrometer within 105-240 GHz. The expected pressure and frequency dependence is observed. The obtained data are validated by two independent calculations of the interaction-induced absorption using a semiclassical trajectory-based method. The observed continuum is interpreted in terms of bimolecular absorption, including a significant contribution from true bound dimers. A simplified formula describing both frequency and temperature dependency of the CO2-Ar continuum within a frequency range from 60 GHz to 450 GHz at temperatures from 200 K to 400 K is suggested for use in atmospheric studies. (C) 2020 Elsevier Ltd. All rights reserved.