Low-lying dipole response in the relativistic quasiparticle time blocking approximation and its influence on neutron capture cross sections

Abstract

We have computed dipole strength distributions for nickel and tin isotopes within the Relativistic Quasiparticle Time Blocking Approximation (RQTBA). These calculations provide a good description of data, including the neutron-rich tin isotopes (130.132)Sn. The resulting dipole strengths have been implemented in Hauser-Feshbach calculations of astrophysical neutron capture rates relevant for r-process nucleosynthesis studies. The RQTBA calculations show the presence of enhanced dipole strength at energies around the neutron threshold for neutron rich nuclei. The computed neutron capture rates are sensitive to the fine structure of the low lying dipole strength. which emphasizes the importance of a reliable knowledge of this excitation mode. (C) 2009 Elsevier B.V. All rights reserved

Large-scale continuum random-phase approximation predictions of dipole strength for astrophysical applications

“…For this reason, both models tend to give rise to similar reaction rates for the most exotic neutron-rich Sn isotopes. Calculations based on a relativistic [60] or nonrelativistic [17] QTBA description of the Sn isotopes show a similar behavior when compared to the HFB+QRPA approach [20], although the low-lying strength obtained within the timeblocking approximation appears to be more fragmented [15][16][17].…”

Self-consistent calculations of the strength function and radiative neutron capture cross section for stable and unstable tin isotopes

“…Comparison with the QRPA version showed that PC inclusion increases the cross section by a factor of two and improves the agreement with experiment [64]. Very recently, the results of calculations of the radiative neutron capture cross sections within the self-consistent relativistic QTBA were performed for the four tin isotopes [65].…”

Continuum quasiparticle random-phase approximation for astrophysical direct neutron capture reactions on neutron-rich nuclei

“…Recently new modes of dipole excitation such as the pygmy resonance and the soft dipole excitation [4][5][6][7] have attracted attentions since influence of the new modes on the r-process nucleosynthesis was pointed out [8]. Motivated with this possibility, microscopic many-body models of electric multipole responses, developed on the basis of the density functional theories, have been applied to the gamma-ray strength function for the compound process calculations [9][10][11][12][13][14].…”