Single- and Double-Octupole Excitations in ^{148}Gd

In the two-valence-neutron nucleus 148Gd, in-beam 148Sm(α,4n) and (3He,3n) measurements have identified nine ν2×octupole levels with 3<I<14. The measured half-life of the (νf7/22×3-)9- state gives B(E3,9-→6+)=55(6)BW. A high-lying 12+ level, which decays by E3 to the 9- state, as well as a 14+ level are shown to be two-phonon octupole excitations of stretched ν2×3-×3- character. All these results can be quantitatively derived from the experimental data for the coupling of one neutron to the core octupole observed in 147Gd.