Fourier Transform Infrared Spectroscopy of the A1Π-X1Σ+ System of MgO

The gas-phase infrared absorption spectrum of the A1Π-X1Σ+ system of MgO was observed in the 2700-5400 cm−1 region with a high-resolution Fourier transform infrared spectrometer. The MgO molecule was produced in a reaction of Mg vapor with N2O. The observed 501 spectral lines were assigned to five vibrational bands, vA-vX = 1-0 2-0, 3-0, 2-1, and 0-1 of 24MgO. These lines were analyzed to determine the band origins, the rotational, centrifugal distortion, and Λ-type doubling constants in the A1Π state. The term value Te of the A1Π state was derived to be 3563.8377 (74) cm−1, with one standard deviation in parentheses. The rotational levels in the A1Π state were found to be perturbed by those of the vibrational levels of the X1Σ+ state through rotational-electronic interaction, and the analysis of the perturbation was carried out to determine the interaction constants. The spectra of the vA-vX = 1-0 bands of the isotopic species, 25MgO and 26MgO, wer also observed and analyzed.