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

Abstract

ABSTRACT The isotope effect of zinc in the chemical exchange reaction using a macrocyclic ligand was not found to be ruled by the Bigeleisen-Mayer approximation, which suggested that the enrichment factor is proportional 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(2B,2,l) polymer were precisely measured by means of an ICP mass spectrometer equipped with nine collectors as ion detectors. The liquid chromatography of a column packed with the cryptand polymer was used for the separation of the zinc isotopes. The enrichment factor ε67,66 for 67Zn to 66Zn was −3.3329(3) × l0−4.That for 68Zn to 66Zn was 1.846(1) × 10 −4 and that for 70Zn to 68Zn was 7.19(2) × 10−4.They were not scaled with δm/mm′, where δm is the mass difference between the isotope pairs, and m and m′ represent the masses of the isotopes. The isotope effect of zinc is implicated with the isotope shift, and the hyperfine structure shift in the isotopomer of the zinc isotopes. The sum contribution of the vibrational energy shift from one isotope to the other and the nuclear mass shift to the enrichment factor of 67Zn was − 1.05 × 10−3, and the contribution of the field shift caused by the nuclear size and shape of the isotope was 5.26 × 10−4. The contribution of the nuclear spin or the hyperfine structure shift to the enrichment factor of 67Zn was small: 1.94 × 10 −4