Collective modes studied by Coulomb excitations

The large gain in sensitivity provided by powerful new γ-ray detector arrays, such as Gammasphere, coupled with other advances in the field of heavy-ion induced Coulomb excitation, open exciting new research opportunities for exploiting Coulomb excitation to probe nuclear structure. Three recent examples are given that exploit this unprecedented sensitivity. The actinide nuclei 248Cm and 240,242,244Pu have been Coulomb excited using 208Pb ions at the barrier. The positive and negative-parity yrast bands have been extended to high spin, ≤ 34ℎ, and the evolution of alignments probed. Heavy-ion induced Coulomb excitation of a 162Dy beam is providing significant new information on states to high spin in the ground, S and γ bands, as well as a double γ-phonon band. Collective octupole correlations are especially strong in 208Pb and 96Zr implying the possible existence of localized octupole double-phonon states in these nuclei. Heavy-ion Coulomb excitation has been used to locate octupole double-phonon strength in these nuclei; the results for 208Pb show large fragmentation of the octupole double-phonon strength whereas a major fraction of the strength may have been located for 96Zr. (author)