Abstract
The C 4Σ −- X 4Σ − (0, 0) band of NbO, whose R heads lie near 4690 Å, has been analyzed from high-resolution grating spectra. Both 4Σ − states have second-order spin-orbit splittings, 4 λ = E( 4 Σ 3 2 )-E( 4 Σ 1 2 ) , of about 60 cm −1, so that they are in good case (a) coupling at low J, although the appearance of the band had been interpreted by previous workers as 4Σ( b)- 4Σ( b). the 93Nb nuclear hyperfine structure ( I= 9 2 ) is very impressive in the R 1, P 1, R 4, and P 4 branches, with the 10 hyperfine components of a rotational line spread over more than 0.9 cm −1 in the F 1 branches. The hyperfine linewidths vary considerably with J, in the manner expected for the rapid spin uncoupling from case (a β) to (b β J ) which occurs in a high-multiplicity state. The very great hyperfine linewidths arise because the sign of the Fermi contact parameter b (the coefficient of I·S in the magnetic hyperfine Hamiltonian) is different in the two 4Σ states, so that the observed patterns are the sums of the splittings in the two electronic states.
Published Version
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