Experimental Evidence of He 2 Decay from Ne 18 Excited States

Two-proton decay from $^{18}\mathrm{Ne}$ excited states has been studied by complete kinematical reconstruction of the decay products. The $^{18}\mathrm{Ne}$ nucleus has been produced as a radioactive beam by $^{20}\mathrm{Ne}$ primary projectile fragmentation at $45\text{ }\text{ }A\mathrm{MeV}$ incident energy on a Be target. The $^{18}\mathrm{Ne}$ at $33\text{ }\text{ }A\mathrm{MeV}$ incident energy has been excited via Coulomb excitation on a $^{\mathrm{nat}}\mathrm{Pb}$ target. The obtained results unambiguously show that the 6.15 MeV $^{18}\mathrm{Ne}$ state two-proton decay proceeds through a $^{2}\mathrm{He}$ 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.