SEPARATION OF SAMARIUM ISOTOPES BY A CROWN-ETHER

Samarium isotopes were fractionated in a liquid-liquid extraction syst em using dicychlohexano-18-crown-6. High precision isotope ratio measu rements with a multicollector mass spectrometer made it possible to ev aluate the contributions of the nuclear size and shape and the nuclear spin to the chemical isotope separation effect. The maximum value of the unit mass enrichment factor (epsilon(u)) was observed to be 0.0016 1 +/- 0.00002. The odd/even enrichment factor of Sm-147 was epsilon(O/ E) = -0.00101 +/- 0.00062 and that of Sm-149 was epsilon(O/E) = -0.000 49 +/- 0.00050. Enrichment factors were affected by nuclear mass, nucl ear volume and nuclear spin in addition to vibrational motion of molec ule. The nuclear volume effect was 1.94 times as large as the nuclear mass effect. The odd/even atomic mass effect was explained with 6s(2)- 6s6p transition in optical isotope shift of Sm I. The correction due t o the nuclear spin of Sm-147 was epsilon(spin) = -0.0016 and that of S m-149 was epsilon(spin) = -0.0014.