Experimental Evidence ofHe2Decay fromNe18Excited States

Abstract

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

Correlated two-proton decay fromC10

“…Aside from the fact that the parent excitation is not well determined, the proton-proton relative energy spectrum does not peak at small energies as expected for 1 S decay. The case for significant 1 S decay from a state at E * = 6.15 MeV in 18 Ne (a case orginally studied by del Campo et al [12]) has been very recently presented by Raciti et al [13]. While these data are also suggestive of 1 S 2p emission, the statistical significance is marginal and, as the parent state is not well resolved, the background makes an uncertain contribution to the observed correlations.…”

Fragmentation cross sections at intermediate energies for hadrontherapy and space radiation protection

“…A 12 C beam was accelerated at 62 AMeV and hit to a 104 µg/cm 2 or 147 µg/cm 2 thick 12 C or 197 Au target. Energy and emission angle of charged fragments (1 ≤ Z ≤ 6) produced in the interaction with the target were measured by a detection setup consisting of two Si-CsI hodoscopes [12] (Fig. 1):…”

“…Since at Fermi energies only few data are available in literature, we decided to fill this gap measuring an extensive set of fragmentation cross sections in this energy regime [10]. In this paper we present original new data on the 12 C+ 197 Au fragmentation reaction, obtained in a large experimental campaign. Other results on the same target are under publication [11].…”

The resonances of 18Ne

“…For decays of 18 Ne from states below 6.15 MeV, there are no intermediate states in 17 F available for sequential decay, so one expects at low energies democratic or correlated two proton emission, but the relative proton-proton energy and angle spectra analysis did not allow to distinguish between di-proton and democratic emission in that experiment.…”

“…The reaction 17 F(p,γ) 18 Ne is particularly important in late nucleosynthesis of massive stars in the presupernovae phase, where the rp-process leads to the production of nuclei up to Cadmium. Many reaction chains include this process that can go via direct or resonance capture of the proton.…”