Experimental Evidence of ²He Decay from ¹⁸Ne Excited States

Two-proton decay from ¹⁸Ne excited states has been studied by complete kinematical reconstruction of the decay products. The ¹⁸Ne nucleus has been produced as a radioactive beam by ²⁰Ne primary projectile fragmentation at 45  AMeV incident energy on a Be target. The ¹⁸Ne at 33  AMeV incident energy has been excited via Coulomb excitation on a ^natPb target. The obtained results unambiguously show that the 6.15 MeV ¹⁸Ne state two-proton decay proceeds through a ²He diproton resonance (31%) and democratic or virtual sequential decay (69%). The quoted branching ratio has been deduced from relative angle and momentum correlations of the emitted proton pairs.