Single vibronic level emission spectroscopy of the low-lying electronic states of NiI

Five low-lying (Te < 2200 cm−1) electronic states of NiI have been observed using single vibronic level (SVL) emission spectroscopy, via three hitherto unobserved band systems in the range 21 150–22 410 cm−1. In addition to the previously characterized X2Δ5/2 and A 2 Π 3 / 2 states, the X 2 Δ 3 / 2 , A 2 Π 1 / 2 , and B 2 Σ 1 / 2 + states have been observed for the first time. The emission spectra yield term energies and vibrational constants that are in excellent agreement with recent ab initio calculations. A number of perturbations in the vibrational level structure can be identified and are attributed to homogenous interactions under the selection rule ΔΩ = 0.