First Observation of Excited States in Li-12

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The neutron-unbound ground state and two excited states of Li-12 were formed by the two-proton removal reaction from a 53.4-MeV/u B-14 beam. The decay energy spectrum of Li-12 was measured with the Modular Neutron Array (MoNA) and the Sweeper dipole superconducting magnet at the National Superconducting Cyclotron Laboratory. Two excited states at resonance energies of 250 +/- 20 keV and 555 +/- 20 keV were observed for the first time and the data are consistent with the previously reported s-wave ground state with a scattering length of a(s) = -13.7 fm.