ИСТИНА

Molecular composition of the currently known planetary atmospheres is dominated by symmetrical species that do not have resonant absorption lines in the long wave infrared and microwave spectral ranges. Nevertheless, absorption caused by weak intermolecular interactions may become crucial in microwindows of atmospheric transparency. The most abundant gas in the Earth’s atmosphere, nitrogen, is transparent in the far-infrared. In contrast, collision induced absorption (CIA) in a nitrogen gas is perceptible in the Earth’s stratosphere. Accounting for the nitrogen CIA is also known to be indispensable for the simulation of the thermal radiance in the Titan’s atmosphere. In this work we present a detailed experimental and theoretical characterization of the millimeter and sub-millimeter wave absorption in N2 −N2 and N2 −Ar pairs. The measurements are carried out using a resonator spectrometer [1] at pressures up to 2 atmospheres in a broad frequency range from 70 up to 360 GHz. Spectra of pure nitrogen were measured at temperatures 296±20 K and N2 with Ar mixture spectrum was measured at room temperature. In this frequency range and under chosen conditions, the absorption of the studied gases has entirely bimolecular nature. The expected continuum pressure and temperature variations are experimentally confirmed. The data obtained so far are in agreement with previous experimental observations [2] as well as with the results of trajectory-based simulation [3]. New practical model is suggested on the basis of theoretical and experimental data, which is intended to facilitate simulation of radiative transfer of mm-submm radiation in the nitrogen rich atmospheres. Funding. This work is supported by the Russian Science Foundation (project No. 22–17–00041). References [1] Koshelev M. A., Leonov I. I., Serov E. A., et al., 2018, IEEE Trans. Terahertz Sci. Technol., 8, 773 [2] Serov E., Balashov A., Tretyakov M., et al., 2020, J. Quant. Spectrosc. Radiat. Transfer, 242, 106774 [3] Chistikov D. N., Finenko A. A., Lokshtanov S. E., et al., 2019, J. Chem. Phys., 151, 194106