Electric-quadrupole and magnetic-dipole contributions to the ν2+ν3 band of carbon dioxide near 3.3 µm

The recent detections of electric-quadrupole (E2) transitions in water vapor and magnetic-dipole (M1) carbon dioxide have opened a new field molecular spectroscopy. While their present status, the spectroscopic databases provide only electric-dipole (E1) for polyatomic molecules (H2O, CO2, N2O, CH4, O3…), possible impact weak E2 M1 bands to modeling Earth planetary atmospheres has be addressed. This is especially important case which may located spectral windows E1 absorption. In work, high sensitivity absorption spectrum CO2 recorded by Optical-Feedback-Cavity Enhanced Absorption Spectroscopy (OFCEAS) 3.3 µm transparency window dioxide. studied interval corresponds region where ν2+ν3 band were recently identified Martian atmosphere. Here, both are detected OFCEAS. Using ab initio calculations 12C16O2, intensity measurements five lines three allow us disentangle contributions. Indeed, values (on order few 10–29 cm/molecule) found reasonable agreement with while (including an contribution) agree very well long path Fourier Transform We thus conclude that should systematically incorporated line list provided databases.