Nuclear Level Structure, B(E2) Gamma-transitions and Nucleon Interaction Data for 56Fe by a Unified Soft-rotator Model and Coupled-Channels Framework.

Abstract

The soft-rotator model (SRM) and a coupled-channels method based on the coupling scheme built on the wave functions of the SRM were applied for a consistent analysis of the nuclear level structure, B(E2) and the nucleon interaction data of 56 Fe. The model could describe the experimental collective levels of 56 Fe up to the excitation energy of 5.5 MeV successfully. Relativistic kinematics and global optical potential form, consistent with nuclear matter theory and Dirac phenomenology, were used in coupled-channels optical model approach to overcome problems left in our previous work. The available nucleon interaction experimental data up to 160 MeV and B(E2) γ -transitions were described satisfactorily.

Coupled-Channels Analysis of Nucleon Interaction Data of28'30Si up to 200 MeV Based on the Soft Rotator Model

“…Furthermore, the CC-SRM calculations reproduced well the nucleon interaction data up to 200 MeV, i.e., neutron total cross sections, proton reaction cross sections, and differential cross sections of nucleon elastic and inelastic scattering. This successful result indicates that the CC-SRM approach is applicable to nuclei in the sd-shell as in the previous analyses for 12 C, 2-4) 52 Cr, 5) 58 Ni, 6) 56 Fe, 7,8) and 238 U, 9) and can be a potentially powerful tool to the analysis of nucleon interaction with nuclei over a wide range of mass number.…”

“…8 15) which has an imaginary component equal to zero at the Fermi energy due to the property stemming from nuclear matter theory. The high-energy saturation behavior is consistent with the Dirac phenomenology:…”

“…Such enhancements are different for different combinations of initial |i and final | f states. In this way, the SRM takes account of the nuclear softness, predicting the redistribution of coupling strength, 8) i.e., the particle current between the channels, which in turn changes the estimates of direct level excitation cross sections compared with the rigid rotator or harmonic-vibrational model.…”

“…By means of the CC calculations with a coupling scheme built using the SRM wave function, we can analyze nucleon scattering to these levels simultaneously and obtain nucleon optical potentials. Up to now, the CC-SRM approach has been applied successfully to analyses of neutron and proton interactions with nuclei together with the collective structure and EM transition rate for 12 C, 2-4) 52 Cr, 5) 58 Ni, 6) 56 Fe 7,8) and 238 U. 9) The nucleon optical potential parameters for these nuclei were extracted through the analyses.…”

First3−excited state ofFe56

“…No evidence for a 4370-keV level and no new levels were observed in the coincidence data of the present experiment. Finally, we note here that the 3076-keV and 4370-keV states are not observed in the spectra of a previous experiment that measured differential cross sections for neutron inelastic scattering [13], whereas the 4510-keV state was strongly populated in that experiment, and that recent theoretical calculations [14] predict the first 3 − state in 56 Fe at excitation energies well above 4 MeV. As for possible explanations on why the 3100-keV, L = 3 state was originally introduced in the experimental results of Ref.…”