0+ states and collective bands in 228Th studied by the (p,t) reaction

The excitation spectra in the deformed nucleus Th-228 have been studied by means of the (p,t) reaction, using the Q3D spectrograph facility at the Munich Tandem accelerator. The angular distributions of tritons were measured for about 110 excitations seen in the triton spectra up to 2.5 MeV. Firm 0(+) assignments are made for 17 excited states by comparison of experimental angular distributions with the calculated ones using the CHUCK3 code. Assignments up to spin 6(+) are made for other states. Sequences of states are selected which can be treated as rotational bands and as multiplets of excitations. Moments of inertia have been derived from these sequences, whose values may be considered as evidence of the two-phonon nature of most 0(+) excitations. Experimental data are compared with interacting boson model and quasiparticle-phonon model calculations and with experimental data for Pa-229.