Infrared emission spectra of C3: the Renner effect in the <i>a</i>3Π<i>u</i> and <i>b</i>3Π<i>g</i> electronic states

Abstract

Five new triplet bands of 12C3, and three corresponding bands of 13C3, have been observed in emission between 6000 and 6600 cm−1 with a Fourier transform spectrometer. Rotational analysis shows that these bands arise from excited bending vibrations of the b̃3Πg→ã3Πu electronic transition, and that all components of the (010) vibrational level of the b̃3Πg state exhibit unusual perturbations. Renner parameters for both electronic states have been extracted from an analysis of the spin-orbit parameters of the (000) 3Π, (010) 3Δ, (020) 3Φ, and (030) 3Γ levels. The Renner effect is shown to be large in both electronic states (ε′ = +0.447, ε″ = +0.566). Approximate bending vibrational frequencies are also obtained (ω2′∼345 cm−1, ω2″∼505 cm−1).