Nuclear size and shape effects in chemical isotope enrichment of neodymiumusing a crown ether

Neodymium was extracted and isotopically fractionated in the liquid-liquid extraction using a crown ether of dicyclohexano-18-crown-6. The maximum val ue in isotope enrichment factor was observed on the isotope pair Nd-142-Nd- 150, and was epsilon (142,150) = 0.00084+/-0.00009: this was 0.00011+/-0.00 001 in terms of the unit mass enrichment factor. The isotope enrichment fac tors showed breakdown of the conventional mass-dependent theory. We present ed the advanced theory by use of the nuclear size and shape effect and the nuclear spin effect. The field shift effect was proved to give larger contr ibution than the nuclear mass effect. The predominance of the field shift e ffect in this study agreed with our previous studies on samarium and gadoli nium.