  Chemical isotope effects of calcium were studied by liquid-liquid extraction
using a crown ether of dicyclohexano-18-crown-6 for the purpose of finding a
cost-effective and efficient way of enrichment of Ca-48 towards the study of
the neutrinoless double beta decay of Ca-48. We evaluated each contribution
ratio of the field shift effect and the hyperfine splitting shift effect to the
mass effect of the calcium isotopes for the first time. The present preliminary
result suggests the contribution of the field shift effect is small, especially
for Ca-40-Ca-48 case, compared with the case of Chromium trichloride-crown in
which the isotope enrichment factors are strongly affected by the field shifts.
These indications are promising towards the mass producion of enriched Ca-48 by
the chemical separation method.
