Nuclear field shift effect in the isotope exchange reaction of cadmium using a crown ether

Cadmium isotopes were fractionated by the liquid–liquid extraction technique with a crown ether, dicyclohexano-18-crown-6. The isotopic ratios of mCd/111Cd (m: 110, 112, 113, 114, and 116) were measured precisely by the multi-collector inductively coupled plasma spectrometry (MC-ICP-MS). When the isotope enrichment factors were calculated, the odd atomic mass isotopes (111Cd and 113Cd) showed excesses of enrichment comparing to the even atomic mass isotopes (110Cd, 112Cd, 114Cd and 116Cd). This odd–even staggering property originates from the nuclear field shift effect. The contribution of the nuclear field shift effect to the observed isotope enrichment factor was estimated to be 5 to 30%.