The MgHB ' (2)Sigma(+)-x (2)Sigma(+) transition: A new tool for studying magnesium isotope abundances

L Wallace, K Hinkle, G Li, P Bernath

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We have identified lines from the 0-3, 0-4, 0-5, 0-6, 0-7, 1-3, 1-4, 1-7, and 1-8 bands of the (MgH)-Mg-24 B' (2)Sigma(+)-X (2)Sigma(+) transition in sunspot umbral spectra. Lines of the 0-7 and 1-8 bands in the uncluttered 7500 Angstrom region are the most obvious, but B' (2)Sigma(+) -X (2)Sigma(+) lines have been tracked as far to the blue as 5300 Angstrom. In combination with weak lines of the 0-7 bands of the (MgH)-Mg-25 and (MgH)-Mg-26 isotopes, the solar isotope ratio Mg-24:Mg-25:Mg-26 has been measured as 76:12:12, in agreement with the much better determined terrestrial ratio 79:10:11. The intensity distribution of bands with nu " from 4 to 8 has been measured and found to show no anomalies; the excitation temperature of 3100 K agrees well with a value of 3200 K determined from SiO in a sunspot spectrum. The lines of the MgH B' (2)Sigma(+)-X (2)Sigma(+) transition are much more cleanly separated and much less blended than lines from the stronger A (2)Pi-X (2)Sigma(+) transition. The B' (2)Sigma(+)-X (2)Sigma(+) lines should prove useful in isotopic abundance analyses for stars where the A (2)Pi-X (2)Sigma(+) transition is too strong to yield useful results.

Original languageEnglish
Pages (from-to)454-461
Number of pages8
JournalThe Astrophysical Journal
Issue number1
Publication statusPublished - 10 Oct 1999


  • molecular data
  • Sun : abundances
  • sunspots
  • POOR

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