CONTRIBUTIONS OF NUCLEAR SIZE AND SHAPE, NUCLEAR-MASS, AND NUCLEAR-SPIN TO ENRICHMENT FACTORS OF ZINC ISOTOPES IN A CHEMICAL-EXCHANGE REACTION BY A CRYPTAND

The isotope effect of zinc in the chemical exchange reaction using a m acrocyclic ligand was not found to be ruled by the Bigeleisen-Mayer ap proximation, which suggested that the enrichment factor is proportiona l to the mass difference and is inversely proportional to the product of the masses of the isotopes. The separation factors of zinc isotopes in the chemical exchange reaction using cryptand(2(B),2,1) polymer we re precisely measured by means of an ICP mass spectrometer equipped wi th nine collectors as ion detectors. The liquid chromatography of a co lumn packed with the cryptand polymer was used for the separation of t he zinc isotopes. The enrichment factor epsilon(67,66) for Zn-67 to Zn -66 was -3.3329(3) X 10(-4). That for Zn-68 to Zn-66 was 1.846(1) X 10 (-4) and that for Zn-70 to Zn-68 was 7.19(2) X 10(-4). They were not s caled with Delta m/mm', where Delta m is the mass difference between t he isotope pairs, and m and m' represent the masses of the isotopes. T he isotope effect of zinc is implicated with the isotope shift, and hy perfine structure shift in the isotopomer of the zinc isotopes. The su m contribution of the vibrational energy shift from one isotope to the other and the nuclear mass shift to the enrichment factor of Zn-67 wa s -1.05 X 10(-3), and the contribution of the field shift caused by th e nuclear size and shape of the isotope was 5.26 X 10(-4). The contrib ution of the nuclear spin or the hyperfine structure shift to the enri chment factor of Zn-67 was small: 1.94 X 10(-4).