Transfer reactions induced with $^{56}$Ni: shell gaps and np pairing

The structure of the unstable doubly magic nucleus $^{56}$Ni has been investigated by measuring one-and two-nucleon transfer reactions. The radioactive beam of $^{56}$Ni was produced at GANIL-Caen, France at 30 MeV/u by means of the LISE spectrometer. The experimental setup used consists of the TIARA-MUST2-EXOGAM combination which provides an almost 4$\pi$ coverage and the ability to perform particle-$\gamma$ coincidences. To probe the N=28 gap, we studied the spectroscopy of $^{55}$Ni through one-nucleon transfer reactions on $^{56}$Ni. The excitation energy spectrum is deduced by measuring the light ejec-tiles only, while particle-$\gamma$ coincidences are used to improve the resolution of the populated states and select the main ones. Comparison between the extracted angular distributions and DWBA calculations allows the extraction of the spectroscopic strength of the hole-and particle-states populated by these one neutron pickup reactions.