Fragmentation of the IAR along the chains $\mathbf{N}=50$ and $\mathbf{Z}=50$

Abstract

We study Isobaric Analog Resonances in even-even nuclei along the $N=50$ isotonic chain. First, Hartree-Fock-Bogoliubov calculations, using the Gogny D1M effective interaction, have been performed to provide energies and occupation probabilities of nucleon orbitals. The Isobaric Analog Resonances are calculated with the charge exchange QRPA approach on top of then HFB calculations. Fermi transition mechanism is interpreted with the existence of collective modes in the final nucleus. The fragmentation of the Fermi Strength results from the fractional occupation of nucleon shells, a direct consequence of nuclear pairing. The theoretical Fermi transition probabilities along the isotopic chain $Z=50$ are also analyzed and confirm our conclusions.

Comments: Due to a wrong sign of paring terms in the equations and code, early results are obsolete. The fragmentation of IAR now seems less pronounced. Work is in progress to analyze the contribution of each term of the Gogny interaction in order to merge all modes into a single resonance