Abstract
Proton resonances in 22Mg have been investigated by the resonant elastic scattering of 21 Na + p . The 21Na beam with a mean energy of 4.00 MeV/nucleon was separated by the CNS radioactive-ion-beam separator (CRIB) and bombarded a thick ( CH2 n target. The energy spectra of recoiled protons were measured at scattering angles of θc.m. ≈ 172° , 146° , respectively. Several excited states observed before have been confirmed including two states (at 6.616, 6.796 MeV) observed at TRIUMF. A new state at 7.06 MeV has been observed, and another new one at 7.28 MeV is tentatively identified due to its low statistics. The proton resonant parameters were deduced from an R -matrix analysis of the differential cross-section data with a SAMMY-M6-BETA code. The astrophysical implication for the 18 Ne(α, p)21 Na reaction has been briefly discussed.
Highlights
The structure of 22Mg has received great interest in recent years because of its important role in determining the astrophysical reaction rates of 21Na(p, γ)22Mg and 18Ne(α, p)21Na reactions in explosive stellar scenarios [1,2].20Ne(3He, n) reaction [10, 11] as well as the 20Ne(3He, nγ) reaction [12,13]
The excitation energies indicated on the figure are calculated by the relation Ex = Er + 5.502 MeV, where the resonant energies Er are deduced from the R-matrix analysis, and the previously determined ones are shown in parentheses for comparison
22Mg corresponded to the 8.596 and 8.741 MeV states in 22Ne, respectively, and they were assigned to Jπ = 2+ and 3−, respectively [8]
Summary
The structure of 22Mg has received great interest in recent years because of its important role in determining the astrophysical reaction rates of 21Na(p, γ)22Mg and 18Ne(α, p)21Na reactions in explosive stellar scenarios [1,2]. Seweryniak et al [17] have concluded that no further measurement is needed to determine this resonant reaction rate under nova conditions. In another aspect, Wiescher et al [1] have proposed that the 18Ne(α, p)21Na reaction is probably one of the key reactions for the break-out from the hot CNO cycle. In order to estimate the resonant reaction rate of 18Ne(α, p)21Na, the knowledge about the resonant properties of those states above the α threshold The resonant property of those states at Ex = 10.12–11.13 MeV has been studied via the direct 18Ne(α, p)21Na measurement [18, 19], but the observed states are too high in energy for nucleosynthesis. The astrophysical implication for the 18Ne(α, p)21Na reaction has been discussed based on the present work
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