The interstellar 7Li/6Li isotope ratio toward ζ ophiuchi and ζ persei

David M. Meyer*, Isabel Hawkins, Edward L. Wright

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


We report high S/N (>2000), high-resolution (≈ 1 km s-1) observations of the interstellar Li I absorption lines toward the stars ζ Oph and ζ Per. Our Li I line profiles indicate the presence of both the 7Li (λrest = 6707.761, 6707.912 Å) and 6Li (6707.921, 6708.072 Å) doublets in these two sightlines. The resultant best-fit values (using a single-component profile) for the interstellar 7Li/6Li isotope ratio are 6.8 (+1.4, -1.7) toward ζ Oph and 5.5 (+1.3, -1.1) toward ζ Per. It is clear from our data that the 7Li/6Li ratio toward ζ Oph and ζ Per is less than the meteoritic value (12.6) representative of the early solar system. This result does not support the lower limit of 25 set for the interstellar 7Li/6 Li ratio by Ferlet & Dennefeld from their Li I observations toward ζ Oph. However, our findings agree much better with the recent 7Li/6Li measurement of 12.5 (+4.3, -3.4) toward ρ Oph by Lemoine et al. Since current models of Galactic chemical evolution predict that the 7Li/6Li ratio should increase with time, these new results suggest that the production of 6Li is being enhanced through cosmic-ray spallation or some other process.

Original languageEnglish (US)
Pages (from-to)L61-L64
JournalAstrophysical Journal
Issue number2 PART 2
StatePublished - Jun 1 1993


  • Galaxy: evolution
  • ISM: abundances
  • Nuclear reactions, nucleosynthesis, abundances

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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