Fourier transform spectroscopy of CrO: Rotational analysis of the A5Σ-X5Π (0,0) band near 8000 cm−1

The emission spectrum of CrO has been investigated by Fourier transform spectroscopy in the near infrared. New weak electronic bands have been found in the 6000- to 10 000-cm^?1 region, the strongest of which, near 8000 cm^?1, is shown to be the (0,0) band of a ⁵Σ-⁵Π transition where the ⁵Π lower state is the ground state. Fifty branches have been assigned in this band, which have permitted the first detailed characterizations of quintet electronic states in the gas phase. Accurate values have now been obtained for the spin-orbit coupling and Λ-doubling intervals in the ground state (which could only be estimated in the previous laser-induced fluorescence work in the visible region by Hocking et al. Canad. J. Phys.58, 516–533 (1980)]). The relative branch intensities are not consistent with those calculated for a pure ⁵Σ-⁵Π(a) transition, and indicate considerable spin-orbit contamination such that there are interference effects between two or more competing transition moments. It is not known whether the ⁵Σ excited state is ⁵Σ⁺ or ⁵Σ^?.