Laser spectroscopy of VO: Analysis of the rotational and hyperfine structure of the C4Σ--X4Σ- (0, 0) band

Abstract

The (0, 0) band of the C 4Σ --X 4Σ - electronic transition of VO was recorded by intermodulated laser-induced fluorescence at a resolution of about 100 MHz over the range 17 300-17 427 cm -1. The hyperfine structure caused by the 51V nucleus (I = 7 2) is almost completely resolved, and provides good examples of case (b βJ) coupling in both electronic states. Internal hyperfine perturbations between the F 2 and F 3 electron spin components (where N = J - 1 2 and J + 1 2, respectively) occur in both electronic states; these are caused by hyperfine matrix elements of the type ΔJ = ±1, and induce hundreds of extra hyperfine lines which permit the courses of the electron spin and hyperfine levels to be followed in detail. In the band center observations of Q lines, center dips and transitions with ΔF ≠ ΔJ have allowed the hyperfine and electron spin constants for the two electronic states to be determined separately despite the parallel polarization of the electronic transition. Numerous local electronic-rotational perturbations occur in the C 4Σ - state, which have required that the line positions be corrected for their effects before meaningful centrifugal distortion constants could be obtained. The C 4Σ - state also suffers from large spin-orbit perturbations by distant electronic states, for which it has been necessary to introduce a second spin-rotation parameter, γ S, following the formalism of Brown and Milton. The corresponding isotropic hyperfine parameter b S is also required. Both γ S and b S result from third-order cross-terms involving the spin-orbit interaction; given sufficient resolution they are always needed in a full description of electronic states of quartet and higher multiplicity. © 1982.