Spectroscopy of the unbound nucleus [sup 18]Na in link with [sup 19]Mg two-proton radioactivity

Abstract

The unbound nucleus 18 Na, the intermediate nucleus in the two-proton radioactivity of 19 Mg, is studied through the resonant elastic scattering 17 Ne(p, 17 Ne)p. The spectroscopic information obtained in this experiment is discussed and put in perspective with previous measurements and the structure of the mirror nucleus 18 N.

New states in18Na and19Mg observed in the two-proton decay of19Mg

“…In the present article, we extend the analysis of the proton- 17 Ne correlations from our 19 Mg experiment [4,8]. In contrast to the previous works [9,10], we find unambiguous evidence for the identification of the g.s. of 18 Na.…”

“…The experimental data are compared to Monte Carlo simulations, assuming two decay mechanisms: (i) simultaneous or direct 2p decay 19 Mg → 17 Ne + p + p according to the predictions of the three-body model [13] and (ii) sequential emission of protons from 19 Mg via one of the low-lying 18 Na levels identified in [10]. In both cases, the 2p-decay energies were obtained by fitting the peaks in the experimental spectra.…”

“…The energy of 18 Na(3 − ) is taken from Ref. [10]. secondary fragmentation of 20 Mg on a 2 g/cm 2 thick 9 Be target positioned in the midplane of the FRS.…”

“…The authors of Ref. [10] also proposed an explanation for the half-life value of the 19 Mg g.s. in terms of sequential emission of protons via tails of broad excited states in 18 Na.…”

“…to be located either 0.42 (17) or 1.27 (17) MeV above the proton-decay threshold [9]. Recently, the spectroscopic properties of the unbound isotope 18 Na were studied by the resonant-elastic-scattering reaction p + 17 Ne [10]. Four excited states in 18 Na were identified while its g.s.…”