ABSORPTION SPECTRUM OF THE NO MOLECULE: IV. THE G2Σ−–X2Π SYSTEM

Abstract

High-dispersion plates of the NO absorption spectrum have been studied between 1600 and 1390 Å for the three isotopic molecules N14O16, N15O16, and N14O18, and G2Σ−–X2Π bands were sorted out from the many overlapping bands in the spectrum. The well-defined band system satisfies the established isotope relations. In contrast with most of the other known NO band systems G2Σ−–X2Π shows almost no perturbations. Vibrational and rotational analyses gave the following constants for the G2Σ− state of N14O16: Te = 62911.7 cm−1; ωe = 1085.54 cm−1, ωexe = 11.083 cm−1, ωeye = −0.1439 cm−1, Be = 1.2523 cm−1, αe = 0.0204 cm−1, γe = 1.3426 Å. The combination defect observed in the G2Σ−–X2Π bands agrees with the defect found in the A2Σ+–X2Π(γ) bands except in sign, which is opposite. Therefore, the symmetry of the G state is confirmed as 2Σ−. The "pure precession" relation between G2Σ− and X2Π is found to hold for the Λ-type doubling of X2Π. The diffuse structure of the band assigned to ν = 10 indicates that G2Σ− is predissociated by a repulsive 2Σ− state dissociating into 2D(N)+3P(O) atoms at 71660 cm−1. The dissociation energy and electron configuration for G2Σ− are discussed.