Calculation of the absolute infrared intensities for the 0−1, 0−2 and 1−2 vibration-rotation transitions in the ground state of no+

The absolute infrared intensities of the 0?1, 0?2 and 1?2 vibration-rotation bands in the ¹Σ⁺ ground state have been calculated from first principles. The dipole moment function for NO⁺ was determined in the region of the equilibrium internuclear separation by an accurate multi-configuration self-consistent-field procedure. The dipole matrix elements over vibration states were solved exactly using numerical techniques. The ratio of the calculated integrated absorption coefficients for the fundamental and first overtone (88.8 cm^?2 atm^?1 and 0.6 cm^?2 atm^?1, respectively, at 273.16°K) is in reasonable agreement with an estimate based on observation of these bands in NO⁺ at high altitudes in the upper atmosphere.