0+states and collective bands in228Th studied by the (p,

Abstract

The excitation spectra in the deformed nucleus 228 Th 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 (IBM) and quasiparticle-phonon model (QPM) calculations and with experimental data for 229 Pa.

High-resolution (p,t) study of low-spin states in Pu240 : Octupole excitations, αSpieker1, Pascu2, Bucurescu3 et al. 2018Phys. Rev. CSelf Cite221150View full textAdd to dashboardCite

“…Second, σ(1 − 2 ) (p,t) might be larger than or equal to σ(1 − 1 ) (p,t) in 232 U and 240 Pu while the strength pattern is inverted in 228,230 Th. Third, significant cross sections to higher-lying excited 1 − states at about 1.6 MeV to 1.8 MeV are observed in 230 Th [32], 232 U [20] and 240 Pu but not in 228 Th [19]. And the fourth point, a discontinuity is once again observed at N B = 11, see Fig.…”

“…HF(0 + 2 ) HF(1 − 1 ) Figure 10. (color online)(a)-(f ) (p, t) cross sections for the 0 + 1 , 2 + 1 , 0 + 2 , 2 + 2 , 0 + 3 , and 2 + 3 states as a function of boson number NB for 228,230 Th (NB = 10, 11) [19,32], 232 U (NB = 12) [20], and 240 Pu (NB = 16). (g)-(l) the B(E2; 2 + 1 → 0 + 1 ) values, excitation energies E(0 + 2 ) and E(1 − 1 ), experimental (symbols) and theoretical B(E3; 3 − 1 → 0 + 1 ) values (lines) from Refs.…”

“…(color online) (a) (p, t) cross sections σ (p,t) depicted as a function of excitation energy for the J π = 1 − states observed in 228,230 Th[19,32], 232 U[20] and 240 Pu. (b) centroid energies calculated from the excitation energies and σ (p,t) of the J π = 1 − states as a function of the boson number NB.…”

“…The (p, t) cross-section ratios R (5 • /25 • ) normalized to the corresponding ground-state ratio are given for the 0 + 2 and 0 + 3 states. The data for 228,230 Th and 232 U have been taken from Refs [19,20,32]…”

Possible experimental signature of octupole correlations in the 02+states of the actinides

“…The recent experimental studies of monopole excitations in deformed nuclei [17][18][19][20] have shown that with state-of-the-art experimental setups new structure information can be gained about many excited J π = 0 + states up to an excitation energy of about 3 MeV. It is important to note that also the spdf-interacting boson model (IBM) predicts a significant contribution of the double-octupole phonons to the structure of the excited J π = 0 + states in the actinides [18,[21][22][23][24]. The new interpretation of the 0 + 2 state and its proposed structure in 240 Pu [10,11] therefore emphasizes the importance of the present experimental (p,t) study to further clarify the nature of the 0 + 2 states in the actinides and to further test the existence of low-lying two-phonon states in deformed nuclei [25].…”