ИСТИНА

We acknowledge full co-authorship of A. A. Balashov, M. A. Koshelev and A. O. Koroleva from Institute of Applied Physics RAS, Nizhny Novgorod, Russia. This study of the millimeter wave continuum absorption in the CO2-X (X=Ar, CO2) mixtures was, in particular, inspired by the success of the classical trajectory-based formalism recently developed to simulate collision-induced absorption (CIA) spectra [1-3]. On the one hand, the agreement, once achieved, between experimental data and the calculated results promotes a better understanding of the nature of the continuum on a much broader scale. On the other hand, the knowledge of the CO2 continuum is required to model the radiative processes in the CO2-rich planetary atmospheres, such as those of Venus and Mars. Experimental spectra of continuum absorption in pure CO2 and a mixture of CO2 with Ar were recorded at room temperature and pressures up to 2 atm using a resonator spectrometer [4]. Measurements covered 105-240 GHz range allowing determining frequency dependence of the continuum absorption. The agreement between the measured and trajectory-based data supports the reliability of both our experimental and theoretical methods. Previously available experimental data on the CO2-X millimeter wave continuum were obtained on a rare frequency grid and, in general, are characterized by unsatisfactory accuracy. Classical trajectory-based formalism made it possible to examine the variation of the far-infrared/mw spectral profile of CO2 -Ar dimer as a function of temperature. The structureless pedestal of the CIA profile corresponding to free/quasibound pairs states is supplemented by the weak signatures of intermolecular vibrational bands of true dimers. Conspicuous fingerprints of intermolecular vibrational bands are seen at extremely low temperatures, which transform to the CIA-like, virtually structureless envelope as the temperature of the simulation increases. This work was partially supported by RFBR projects No. 18-55-16006. [1] Daniil Oparin et al, J Quant Spectrosc Radiat Transfer, 2017, 196, 87-93. [2] Daniil Chistikov et al, J Chem Physics, 2019, 151(19), 194106. [3] Tatyana Odintsova et al, J Quant Spectrosc Radiat Transfer, 2021, 258, 107400. [4] Maksim Koshelev et al, IEEE Transactions on Terahertz Science and Technology, 2018, 8(6), 773.