The anomalous hyperfine structure of Al II

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The hyperfine structure of a large number of transitions in Al II cannot be described using A and B hyperfine constants and the hyperfine structure is therefore said to be anomalous. In this paper, we have studied the hyperfine structure of a few transitions in Al II, 3s5s(3)S-3s5p(3)P, 3s4d(3)D-3s5p(3)P and 3s5p(3)P-3s5d(3)D, by combining theory and experiment. It is shown that the anomalous hyperfine structure is due to strong off-diagonal hyperfine interaction resulting not only in a deplacement of the energies of the hyperfine levels, but also resulting in large intensity redistribution among the individual hyperfine lines. It is shown that the hyperfine mixing in 3s4d(3)D and 3s5d(3)D is very large, whereas small but not negligible in 3s5p(3)P. By combining experimental spectra and theory we could obtain accurate wavefunctions for the 3s4d(3)D and 3s5d(3)D hyperfine levels which were used to calculate the gf-values of all individual hyperfine transitions not only for 3s5p(3)P, but also for 3s3p(3)P and 3s4p(3)P, where the off-diagonal hyperfine interaction leads to negligible intensity redistribution.


Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Astronomy, Astrophysics and Cosmology
Original languageEnglish
JournalJournal of Physics B: Atomic, Molecular and Optical Physics
Issue number13
Publication statusPublished - 2012
Publication categoryResearch