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Published July 1981 | public
Journal Article

The isotopic composition of titanium in the Allende and Leoville meteorites


We describe the analytical techniques developed for the precise measurement of the titanium isotope abundances using a TiO^+ ion beam. Terrestrial, lunar, and bulk meteorite samples yield identical results. Using a normalization to ^(46)Ti/^(48)Ti for mass dependent isotope fractionation, we obtain the normal Ti composition: ^(46)Ti/^(48)Ti = 0.108548; ^(47)Ti/^(48)Ti = 0.099315 ± 0.000005; ^(49)Ti/^(48)Ti = 0.074463 ± 0.000004; ^(50)Ti/^(48)Ti = 0.072418 ± 0.000004 (2σ grand mean), taking ^(18)O/^(16)O = 0.00037. Measurements on thirteen coarse-grained and fine-grained Ca-Al-Ti-rich inclusions from the Allende and Leoville meteorites show the presence of widespread, significant, nonlinear isotope anomalies in the Ti isotopes which were not used for normalization. The data require the addition of at least three exotic components. The distinct correlation of non-linear effects for the most neutron-rich isotopes of Ca and Ti and the absence of substantial effects at ^(46)Ca in the FUN samples EK-1-4-1 and C-1 indicate that the effects reflect neutron-rich equilibrium or quasi-equilibrium nucleosynthetic processes in the outer layers of a supernova core. The results on Ca and Ti in conjunction with the isotopic effects on other elements (Mg, Sr, Ba, Nd, Sm) show that the samples represent mixtures of different nucleosynthetic components from distinctive processes ('e', 'r', 'p') which do not appear to be related to processes in the same stellar sites.

Additional Information

© 1981 Pergamon Press Ltd. Received 5 September 1980: accepted in revised form 11 February 1981. Our colleagues FOUAD TERA and THOMAS KAISER generously shared their encyclopedic knowledge of Ti chemistry with us. Participants at the Santa Cruz workshop on Astronomy and Astrophysics and in particular W. A. FOWLER, W. D. ARNETT, and S. E. WOOSLEY provided guidance in the complexities of equilibrium and quasi-equilibrium processes. We thank J. H. REYNOLDS and TYPHOON LEE for helpful and scholarly reviews of this paper. This work was supported by the National Science Foundation (PHY 76-83685) and the National Aeronautics and Space Administration (NGL 05-002-188). FRN was supported also by the Swiss National Science Foundation.

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