Speaker
Description
The r-process, competing reactions of beta-decay and radiative neutron capture, takes place in neutron-rich nuclei with small neutron separation energy, typically around 2MeV. We shall describe the neutron capture reaction by means of the nuclear density functional theory, and predict a new mechanism in which roles are played by low-lying collective excitations specific to neutron-rich nuclei, such as the pygmy quadrupole mode and the octupole vibrations as well as the quasiparticle resonance caused by the pair correlation.
The theoretical method is based on the continuum quasiparticle random phase approximation where the neutron scattering state and collective excitations as well as the gamma transitions are described in the same framework. It provides a scheme where the collectivity and the pair correlation are taken into account in the capture process. We demonstrate the method with numerical calculation using the Skyrme density functional model with the density dependent delta pairing interaction. As an example we describe 89Ge(n,g)90Ge where the pygmy quadrupole mode forms a resonance capture, and 91Zn(n,g)92Zn where the quasiparticle resonance contributes to the low-energy s-wave capture cross section.
T. Saito and M. Matsuo, Phys. Rev. C 104, 034305 (2021)
T. Saito and M. Matsuo, Phys. Rev. C 107, 064607 (2023)
T. Saito and M. Matsuo, arXiv: 2504.18239