The optical spectrum of NiD has been reinvestigated. In the yellow-red wavelength region three sub-systems, A2Δ5/2-X2Δ5/2. 2Φ7/2-X2Δ5/2, and 2Δ3/2-X2Δ3/2, have been found. Four bands of these sub-systems were rotationally analysed. The analysis was also extended to the (3, 0) band of the earlier known B2Δ5/2-X2Δ5/2 sub-system. In addition, the (0, 0) band of the 2Δ3/2-X2Δ5/2 transition was analysed.The results for NiD have been compared with those earlier obtained for NiH. Two term value calculations have been made, one for NiH and one for NiD. Since intercombination bands are known, all the term values could be calculated relative to each other. The term values are presented in a diagram.

Two new NiH sub-systems, called 2Δ3/2-X2Δ5/2 and 2Φ7/2-X2Δ5/2, have been analysed. The 2Δ3/2 sub-state belongs probably to the earlier known A2Δ state or B2Δ state. A perturbation in the v" = 1 level of the ground X2Δ5/2 state indicates other nearby low-lying states. The observation of the two rather intense 2Δ3/2-X2Δ5/2 bands is an evidence that the states might be better described by Hund's coupling case (c) than by case (a).

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