Damping mechanism of the isoscalar giant monopole resonance in 58Ni

Following the success achieved in explaining the origin of fine structure observed in the isoscalar giant quadrupole resonance (ISGQR) and the isovector giant dipole resonance (IVGDR), fine structure in the region of the isoscalar giant monopole resonance (ISGMR) were investigated using the wavelet analysis in order to investigate the role of different mechanisms contributing to its decay width. In this context, high-energy resolution ISGMR data on many nuclei were acquired at the iThemba Laboratory for Accelerator Based Sciences (iThemba LABS). The experimental scales extracted from these data are compared to different theoretical approaches performed in the framework of quasiparticle random phase approximation (QRPA) and beyond-QRPA including complex configurations using both non-relativistic and relativistic density functional theory. The role of Landau fragmentation was highlighted while the inclusion of coupling between one particle-one hole (1p-1h) and two particle-two hole (2p-2h) configurations modify the strength distributions and wavelet scales indicating the importance of the spreading width.