Magnetic dipole and quadrupole transitions in the ν2 + ν3 vibrational band of carbon dioxide

This paper aims at the theoretical study of the CO2 magnetic-dipole ?(2) + ?(3) rovibrational absorption band that was recently detected in the Martian atmosphere. Specific characteristics of the magnetic dipole operator are carefully examined. Our evaluation of the magnetic-dipole line intensities is based on the variational calculations and the use of molecular properties is determined through specially performed ab initio quantum chemical calculations. The comparison of our simulated magnetic-dipole spectrum with available laboratory taken data also requires the knowledge of line intensities in the quadrupole band, which partially overlaps with that magnetic-dipole. Quadrupole intensities, once reconsidered, are permitted to correct previously reported values of the integrated intensity as well as the intensity of selected branches. The sum of our calculated magnetic-dipole and quadrupole rovibrational lines is shown to be in good agreement with both sets of presently available data from FTIR and OFCEAS laboratory observations.

Automated summary

This paper presents a theoretical study of the CO2 magnetic-dipole ?(2) + ?(3) rovibrational absorption band detected in the Martian atmosphere. The characteristics of the magnetic dipole operator are carefully examined, and line intensities are evaluated using variational calculations and ab initio quantum chemical calculations. The comparison of the simulated magnetic-dipole spectrum with laboratory data requires consideration of quadrupole intensities, leading to corrections of integrated intensity and branch intensity values. The calculated magnetic-dipole and quadrupole rovibrational lines are in good agreement with available data from FTIR and OFCEAS laboratory observations.