Isotopic Composition of Lithium in Some Meteorites and the Role of Neutrons in the Nucleosynthesis of the Light Elements in the Solar System

Abstract

In the model proposed by Fowler, Greenstein, and Hoyle for the nucleosynthesis of the light elements in the solar system, the part played by neutrons was essential. The consequence of the recent experimental results of Yiou et al. on the production cross-sections of the Boron isotopes by protons in oxygen is that the neutron flux calculated by Fowler, Greenstein, and Hoyle is much too high.

In connection with this problem we have searched for possible variations in the Li isotopic composition of several meteorites. The measurements were performed with an ion-sputtering mass spectrometer of our own design which enables a point-by-point analysis of the meteoritic material. Variations as high as 20% have been observed in the meteorites, while in terrestrial stones the natural ratio was found to be constant. The results are consistent with those that we have recently obtained on the Holbrook meteorite. The variations have been examined very carefully and no instrumental effect has been found which could explain these anomalies. If a neutron irradiation were to be retained as a possible explanation, the flux required would be compatible with the limit set by the Boron results mentioned above.