An Analysis of Hyperfine Interactions in the Electronic Spectrum of AIF

Authors:
  • JBJ M Brown
    J M Brown
  • IKI Kopp
    I Kopp
  • CMC Malmberg
    C Malmberg
  • BRB Rydh
    B Rydh
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Abstract
Lines in theb3Σ+-a3II andc3Σ+-a3II systems of AlF show partially resolved hyperfine structure. This structure has been attributed to magnetic interactions involving the27Al nucleus for whichI= 5/2. About twenty unblended lines from the (0, 0) bands of the two systems have been analysed in detail, using a computer programme to simulate the profiles by calculating the frequencies and intensities of individual hyperfine transitions. For low values of the rotational quantum number, the lines show a simple triplet structure, which reflects the case (bβS) coupling in the3Σ states. Analysis of these lines gives values for the Fermi contact parameters in the two states involved (bF= 0.049 cm-1and 0.057 cm-1in theb3Σ+andc3Σ+states respectively). As the rotational quantum number increases, the hyperfine patterns become less regular, indicating a departure from case (bβS) coupling in the3Σ states and from case (aβ) coupling in the3II state. By reproducing the details of these line-shapes, it has also proved possible to determine values for the electron spin-spin and spin-rotation parameters in the two3Σ states:b3Σ+λ = -0.025(10)cm-1γ = 0.0000(3)cm-1c3Σ+λ = 0.00(1)cm-1γ = 0.0015(10)cm-1The experimental values for the Fermi contact parameter of AlF in thea3II andb3Σ+states are well produced by a simple single configuration molecular orbital calculation but the value for thec3Σ state is rather larger than expected on this basis.

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