Low-lying isovector collective states and the interacting-boson model.

Isovector low-lying collective 2/sup +/ states are studied in the Samarium isotopes in terms of the interacting-boson model. On the basis of E2 transition data, it is pointed out that the 2/sub 3//sup +/ states of /sup 148,150/Sm are isovector. The first calculation including different proton and neutron boson charges is reported for the E2 transitions 0/sub 1//sup +/..-->..2/sub 1//sup +/. 2/sub 2//sup +/, and 2/sub 3//sup +/ of /sup 148154/Sm, giving rise to the first comprehensive agreement with experiment. Some predictions of B(M1) values are presented for further confirmation of the isovector properties.