ИСТИНА

Collision-induced absorption (CIA) in dry atmospheric gases plays significant role in the upper atmosphere. Its accurate modeling is important for remote sensing in the Earth’s atmosphere as well as for studying the atmospheres of other space objects - exoplanets and satellites, in particular, the Saturn’s satellite Titan, the atmosphere of which consists mainly of nitrogen. However, to the best of our knowledge, the only experimental study of the dry air absorption at atmospheric conditions in the millimeter wavelength range can be found [1]. Widely used Millimeter-wave Propagation Model (MPM) [2] includes dry air absorption component, which is based on quantum chemical calculations using isotropic interaction potential and multipole-induced dipole functions [3]. Recently, another approach for calculation of CIA spectra employing classical trajectory formalism was suggested [4]. The scattering trajectories are obtained by solving classically exact equations of motion in Hamiltonian form. The use of ab initio interaction potential energy and induced dipole surfaces approximated by smooth functions is the salient feature of the developed formalism. Present work is devoted to experimental study of millimeter wave absorption in dry nitrogen and dry oxygen. The measurements were carried out using a resonator spectrometer with the sensitivity of 4×10−9 cm−1 [5]. The latter was achieved by using fast (~ 10 mks/step) precise frequency scanning with continuous phase and high stability of both apparatus and ambient conditions. The experimental spectra were recorded at temperatures from 265 to 310 K and pressures from 750 to 1500 Torr. The obtained results coincide within the statistical uncertainty with the corresponding results from work [1] that confirms accuracy and reliability of both data sets. Comparison of the experimental results with those calculated using MPM, pure quantum approach [6] and based on classical trajectories [4] is presented. Calculations by classical trajectories approach was supported by RFBR Project no. 18-05-00119. Experimental activity was supported by RFBR Project no. 18-05-00698. Spectra analysis was done within RAS Project no. 0035-2018-0002. References: 1. A.I. Meshkov, F.C. De Lucia, J. Quant. Spectrosc. Radiat. Transfer. 108, p. 256−276 (2007). 2. P. Rosenkranz, Remote Sens. Code Library, 2017, doi:10.21982/M81013. 3. A. Borysow, L. Frommhold, The Astrophysical Journal, 311, 1043–1057 (1986). 4. D.N. Chistikov, A.A.Finenko, Y.N. Kalugina, S.E. Lokshtanov, S.V. Petrov, A.A.Vigasin, 25th Int. Conference on High Resolution Molecular Spectroscopy, 2018, Abstract Book, p. 211. 5. M.A. Koshelev, I.I. Leonov, E.A. Serov, A.I. Chernova, A.A. Balashov, G.M. Bubnov, A.F. Andriyanov, A.P. Shkaev, V.V. Parshin, A.F. Krupnov, M.Yu. Tretyakov, IEEE Transactions on Terahertz Science and Technology, 8(6), 773–783, (2018). doi: 10.1109/TTHZ.2018.2875450 6. T. Karman, “Collision-induced absorption by oxygen and nitrogen molecules” PhD dissertation, Nijmegen, 2018.