Magnetic dipole and electric quadrupole absorption in carbon dioxide

Abstract Magnetic dipole and electric quadrupole absorption in carbon dioxide are addressed in details. The selection rules for both processes are presented. The equations for the line intensities are given. In the case of the quadrupole absorption the Herman-Wallis functions are derived. The results of the present paper were used in the analysis of the carbon dioxide absorption band at 3.3 µm in the atmosphere of Mars (Trokhimovskiy A, Perevalov V, Korablev O, Fedorova AF, Olsen KS, Bertaux JL, Patrakeev A, Shakun A, Montmessin F, Lefevre F, Lukashevskaya A. First observation of the magnetic dipole CO2 absorption band at 3.3 µm in the atmosphere of Mars by ExoMars Trace Gas Orbiter ACS instrument. A&A 639, A142 (2020)). The retrieved from the Martian atmosphere spectra vibrational transition magnetic dipole moment for the 01111-00001 (ν2+ν3) band of 12C16O2 M 01111 ← 000001 | Δ l 2 | = 1 = 0.96 μ N (where μN is nuclear magneton) is one order of magnitude larger than the gyromagnetic ratio in the case of the rotation-induced magnetic dipole moment.