Scissors resonance in the quasi-continuum of Th, Pa and U isotopes

M. Guttormsen , L. A. Bernstein , A. Görgen , B. Jurado (1) , S. Siem , M. Aiche (1) , Q. Ducasse (1) , F. Giacoppo , F. Gunsing (2) , T. W. Hagen , A. C. Larsen , M. Lebois (3) , B. Leniau (3) , T. Renstrøm , S. J. Rose , T. G. Tornyi , G. M. Tveten , M. Wiedeking , J. N. Wilson (3)

1 ACEN - Aval du cycle et Energie Nucléaire
2 IRFU - Institut de Recherches sur les lois Fondamentales de l'Univers
3 IPNO - Institut de Physique Nucléaire d'Orsay

The gamma-ray strength function in the quasi-continuum has been measured for 231-233Th, 232,233Pa and 237-239U using the Oslo method. All eight nuclei show a pronounced increase in gamma strength at omega_SR approx 2.4 MeV, which is interpreted as the low-energy M1 scissors resonance (SR). The total strength is found to be B_SR = 9-11 mu_N^2 when integrated over the 1 - 4 MeV gamma-energy region. The SR displays a double-hump structure that is theoretically not understood. Our results are compared with data from (gamma, gamma') experiments and theoretical sum-rule estimates for a nuclear rigid-body moment of inertia.

Domaines: Physique Nucléaire Expérimentale [nucl-ex]

M. Guttormsen, L. A. Bernstein, A. Görgen, B. Jurado, S. Siem, et al.. Scissors resonance in the quasi-continuum of Th, Pa and U isotopes. Physical Review C, 2014, 89, pp.014302. ⟨10.1103/PhysRevC.89.014302⟩. ⟨in2p3-00908733⟩