ANOMALOUS QUADRUPOLE COUPLING IN EUROPIUM ETHYLSULFATE

Hynerfine structure, apparently of pure quadrupolar form, has been observed in the Eu/sup 3+/ ion in a neodymium ethylsuifate lattice. It has twice the predicted magnitude and opposite sign to that calculated on the basis of a pure ground electronic configuration of the type 4f/sup n/. Arguments are presented for ascribing the anomaly to the admixing, through the crystal-field potential, of the state 5p/sup 5/6p /sup 1/D/sub 2/ into the closed-shell state 5p/sup 6/ /sup 1/S/sub 0/. For Eu/sup 152/, P/sub 15 0.5) x 10/sup -4/ cm/sup -1/ and for Eu/sup 154/, P/sub 154/ = -(8.3 plus or minus 0.7) x 10/sup -4/ cm/sup -1/. The spin and parity assignments of 2- for the 1531kev state in Sm/sup 152/ and the 1400- and 1723-kev states in Gd/sup 154/, as well as the electric dipole multipolarities of the radiations depopulating these states, are confirmed. The quadrupole moment of Eu/sup 154/ is found to be 3.29 plus or minus 0.37 b. (auth)