Proton–hole excitation in the closed shell nucleus 205Au

The neutron-rich N=126N=126 nucleus 205Au has been populated following the relativistic energy projectile fragmentation of E/A=1 GeVE/A=1 GeV208Pb, and studied via charged-particle decay spectroscopy. An internal decay with a transition energy of 907(5) keV and a half-life of T1/2=6(2) sT1/2=6(2) s has been identified through the observation of the corresponding K and L   internal conversion electron lines. The 907 keV energy level corresponds to the πh11/2−1 proton–hole state and decays both internally into the πd3/2−1 ground-state and via β decay into 205Hg. The obtained data provides information on the evolution of single-proton hole energies which are vital inputs of shell model descriptions for nuclei around the 20882Pb126 doubly magic core.