抄録
The difference in the isotopic compositions of barium from some meteorites and from the terrestrial barium is explained as due to the alteration of the isotopic ratios by a combined effect of mass-dependent fractionation, neutron-capture and cosmic-ray irradiation processes, which took place prior to and during the period of formation of the solar system. The abundances of 134Ba and 135Ba in the meteorite Bruderheim seem to be slightly enhanced due to the decays of 2.06-year 134Cs and 2.3 × 106-year 135Ba. A small difference in the isotopic compositions of cerium in the Bruderheim meteorite and the terrestiral sample can also be attributed to neutron-capture processes, which occurred during an early irradiation period. It is shown that the barium and xenon isotopic anomalies observed in meteorites are closely related to each other.
