Dipole Strength in the 235U(gamma,gamma') Reaction up to 2.8 MeV

Spectra of the 235U(gamma, gamma') reaction were measured at the S-DALINAC at bremsstrahlung endpoint energies E0 = 3:5 MeV and 4.4 MeV and scattering angles of 90± and 135± with respect to the beam axis. Discrete transitions are observed at excitation energies below 2.3 MeV only. The deduced cross sections are in rough agreement with the findings of Bertozzi et al. [Phys. Rev. C 78, 041601(R) (2008)] except for the most prominent transition, where the present result is a factor of about two lower. Evidence for unresolved dipole strength is found in the spectra by means of a fluctuation analysis, which was carried out up to an excitation energy of 2.8 MeV. If this unresolved strength exhibits the same ratio of E1=M1 cross sections as observed in the even-mass neighbor 236U, then the energy centroid Ex = 2:5(3) MeV and total strength SUM[B(M1)¦ = 3.6(1:3) (mu_N)^2 of the M1 part are in good agreement with the systematics of the scissors mode in even-even actinide nuclei.

YEVETSKA O.;  ENDERS J.;  FRITZSCHE M.;  VON NEUMANN-COSEL P.;  OBERSTEDT Stephan;  RICHTER A.;  ROMIG C.;  SAVRAN D.;  SONNABEND K.; 

2010-05-10

AMER PHYSICAL SOC

JRC56555

0556-2813,   

https://publications.jrc.ec.europa.eu/repository/handle/JRC56555,   

10.1103/PhysRevC.81.044309,