National Institute for Theoretical Physics, Stellenbosch Institute of Advanced Study, 7602, South Africa; Institute of Nuclear Physics, Moscow State University, Moscow 119992, Russian Federation; Institut d'Astronomie et d'Astrophysique, ULB, CP 226, B-1050 Brussels, Belgium; Institute of Physics and Power Engineering, 249033, Obninsk, Russian Federation
Avdeenkov, A., National Institute for Theoretical Physics, Stellenbosch Institute of Advanced Study, 7602, South Africa, Institute of Nuclear Physics, Moscow State University, Moscow 119992, Russian Federation; Goriely, S., Institut d'Astronomie et d'Astrophysique, ULB, CP 226, B-1050 Brussels, Belgium; Kamerdzhiev, S., Institute of Physics and Power Engineering, 249033, Obninsk, Russian Federation
The E1 strength functions and radiative capture cross sections for several compound Sn isotopes, including unstable 132Sn and 150Sn, have been calculated using the self-consistent microscopic theory. In addition to the standard RPA or QRPA approaches, the method includes the quasiparticle-phonon coupling and the single-particle continuum. The results obtained show that the phonon contribution significantly affects the pygmy dipole resonance, which is of particular relevance for a proper description of the radiative neutron capture. The impact of the phonon coupling on the pygmy dipole resonance and the radiative neutron capture cross sections increases with the (N -Z) difference. For example, in the (0-10) MeV interval the full theory gives 17% of the energy- weighted sum rule for 150Sn and 2:8% for 124Sn, whereas the continuum QRPA approach gives 5:1% and 1:7%, respectively. These results indicate the importance the self-consistent calculation can have, especially when applied to neutron-rich nuclei of astrophysical interest. The comparison with the widely-used phenomenological Generalized Lorentzian approach shows that the (Q)RPA approach gives an increase in the neutron capture cross section by a factor of 2 for 132Sn and a factor of 10 for 150Sn and that the inclusion of the phonon coupling still increases these cross sections even furhter, by a factor of 2-3.
