Molecular constants of nitrogen dioxide from the near infrared spectrum

Abstract

High resolution spectra of the (1, 0, 1), (2, 0, 1), (0, 0, 3), and (1, 0, 3) bands of 14NO 2 and 15NO 2 have been obtained. An analysis of the combined ground state combination differences and reported microwave transition frequencies has led to improved values of the rotational and centrifugal distortion constants for the ground state of each molecule, including empirical P 6 terms. The (1, 0, 1) and (2, 0, 1) bands of each molecule have been analyzed giving improved values for the band origins and upper state rotational constants. From the rotational constants determined here it has been possible to calculate the rotational constants for the (0, 0, 3) and (1, 0, 3) vibrational states. A predicted spectrum calculated using these values has led to the identification of the Q-branch transitions observed in the (0, 0, 3) regions as the Q Q K ( N) transitions of the (0, 0, 3) band, and not the Q-branches of a type- B band as had been reported previously. Measurement of the observed spin-splittings in the (2, 0, 1) bands has led to a determination of the effective spin-rotation coupling constants for the (2, 0, 1) vibrational levels.