Hyperfine structure of the [14.6] 2Δ 5/2 -X 2Δ 5/2 (9, 0) band of NiI

Abstract

The (9, 0) band of the [14. 6] 2Δ5/2-X2Δ5/2 transition of Nil in the visible region has been studied at high resolution using laser vaporization/reaction supersonic free jet expansion and laser induced fluorescence spectroscopy. Spectrum taken at a resolution of about 80 MHz shows the resolved hyperfine structure which is caused by an unpaired electron in the excited state interacting with the large magnetic moment of the I nucleus with nuclear spin I = 5/2. The rapid decrease in hyperfine width of the low J lines in the v = 9 level suggests that the hyperfine coupling in the [14.6] 2Δ 5/2 state conforms to the Hund's Case a β coupling scheme. Accurate rotational and hyperfine parameters for the [14. 6] 2Δ 5/2 state have been obtained, which indicate that the v = 9 level is perturbed.