Spectroscopy Of Mg-36: Interplay Of Normal And Intruder Configurations At The Neutron-Rich Boundary Of The "Island Of Inversion"

We report on the first spectroscopy study of the very neutron-rich nucleus Mg-36(12)24 using the direct two-proton knockout reaction Be-9(Si-38,Mg-36 + gamma)X at 83 MeV/nucleon. The energy of the first excited 2(+) state of Mg-36, E(2(1)(+)) = 660(6) keV, was measured. The magnitude of the partial cross sections to the ground state and the 2(1)(+) state is indicative of strong intruder admixtures in the lowest-lying states as suggested by Monte Carlo shell-model calculations.