Influences of nuclear size and shape and nuclear spin on chemical isotope effect of zirconium-crown complex

Zirconium isotopes were fractionated by liquid-liquid extraction system using dicyclohexano-18-crown-6. The experimental enrichment factors showed failure from the Bigeleisen-Mayer approximation, which had been believed since their article of 1947. The nuclear size and shape and the nuclear spin result in the additional isotope effects on the Bigeleisen-Mayer approximation. The contributions of the nuclear mass and of the field shifts of s-orbital and d-orbital to the chemical isotopic enrichment factors were calculated by adding the correction terms onto the Bigeleisen-Mayer approximation. The scaling factor ratios which represent weight of contributions of the mass effect and the field shift effect in the separation factors were independent of the initial condition of aqueous phase and indicated constant values throughout every condition, while the scaling factors themselves had individual values. The scaling factor of the nuclear spin was also calculated by means of the hyperfine splitting spectra of (91)Zr, w'=-0.118+/-0.003. The constant value of w' showed that the nuclear magnetic field was not disturbed in the chemical exchange reaction.