Narrow elastic-scattering states at high excitation inK.-M. Källman1, M. Brenner1, V.Z. Goldberg2, T. Lönnroth1, P. Manngård1, A.E. Pakhomov2 and V.V. Pankratov2
1 Department of Physics, Åbo Akademi, FIN-20500 Turku, Finland
2 Russian Scientific Center "Kurchatov Institute", 123182 Moscow, Russia
(Received: 26 June 2000 / Revised version: 13 June 2002 / Published online: 4 February 2003)
The excitation function and angular distributions of elastic -particle scattering on have been measured in the laboratory energy range 6-28 MeV using a backscattering technique on a thick target, yielding a continuous energy distribution. More than 200 narrow states are observed, with widths in the range -100 keV at excitation energies E* =13-32 MeV. Angular distributions at backward angles were measured, and angular momentum values of more than 83 states have been deduced. The analysis gives spin-parities , -partial widths and reduced widths of the narrow high-lying resonant states in . The experimentally observed states display both the negative- and the positive-parity rotational-like sequences with seemingly no parity splitting, a finding which is at variance with most potential-model predictions. The deduced effective moment of inertia indicates a more extended structure than the ground-state configuration. The observed strength of each -value is analyzed in terms of an underlying split doorway state of Lorentzian form, which yields an interpretation as fragmented rotational states.
21.10.Hw - Spin, parity, and isobaric spin.
24.10.-i - Nuclear-reaction models and methods.
24.30.-v - Resonance reactions.
25.55.-e - -, -, and -induced reactions.
© Società Italiana di Fisica, Springer-Verlag 2003