THE SPECTRUM OF NIF - IDENTIFICATION OF THE 3 LOWER 2-DELTA, 2-SIGMA, AND 2-PI STATES

Revisiting the experimental spectra of three transitions of NiF already analyzed (J. Mol. Spectrosc.77, 29 (1979); J. Phys. B14 2569 (1981)) we show that two transition 2Π 3 2-2Δ 5 2 (22 125 cm-1) and 2Π 3 2-2Σ (21 381 cm-1) share a common upper electronic level as observed by Bai and Hilborn (Chem. Phys. Lett.128, 133 (1986)). The third transition lying at 21 275 cm-1 is a 2Δ 3 2-2Π 1 2 or a 2Π 1 2-2Δ 3 2 transition. Our analysis shows that the Λ-doubling responsible for the fine structure arises from the lower state. A fourth transition (21 931 cm-1) is partially analyzed as a 2Π 1 2-2Σ transition. Three different lower electronic states (2Δ, 2Σ, 2Π) can be supposed to arise from the 3d9 lower orbital of Ni+ as expected in a strongly ionic molecule. Two of them are identified (2Δ and 2Σ). The 2Π state can be the lower state of the 21 275 cm-1 transition or possibly an unobserved state strongly mixed with the 2Δ 3 2 lower level in which it induces a large fine structure under the hypothesis that the 21 275 cm-1 band is that of a 2Π 1 2-2Δ 3 2 transition. © 1991.