Discovery of a New Broad Resonance inNe19: Implications for the Destruction of the Cosmicγ-Ray Emitter

J. C. Dalouzy

¹

,

L. Achouri

²

,

M. Aliotta

³

et al.

Abstract

Six proton-emitting states in 19Ne were studied through the inelastic scattering reaction H(19Ne,p);{19}Ne; (p)18F. Their energies and widths were derived from the protons detected at zero degree, while proton-proton angular correlations between the detector at zero degree and a segmented annular detector were used to determine their spin value. In addition to the known states, a new broad J=1/2 resonance has been evidenced at E_{x} approximately 7.9 MeV, approximately 1.45 MeV above the proton emission threshold. By introducing this resonance, the 18F(p,alpha)15O destruction rate in novae is significantly enhanced. This reduces the chance to observe the cosmic gamma-ray emission of 18F from novae in space telescopes.

Resonances in19Ne with relevance to the astrophysically important18F(p,Mountford1, Murphy2, Achouri3 et al. 2012Phys. Rev. CSelf Cite

“…Feature C has previously been observed several times [6,7,18,19], but while there is reasonable agreement in energy and proton width, the present fit suggests a significantly broader alpha width than the earlier works, even given their disagreement. Re-analysis of the data in Murphy et al [7] has revealed an ambiguity such that a significantly broader alpha partial width than reported would also adequately describe the structure.…”

“…The feature labelled B is likely to be the resonance previously observed by Bardayan et al [14], and by Dalouzy et al [6] (see Table I for observed energies and widths). The energy reported here is somewhat lower than previously observed, though it is poorly constrained as is illustrated by the large covariance between the energy and relative widths of this state.…”

“…Re-analysis of the data in Murphy et al [7] has revealed an ambiguity such that a significantly broader alpha partial width than reported would also adequately describe the structure. Based on two previous observations of a state with likely J π = 3/2 + approximately 100 keV higher in energy [6,19], we have included resonance D to our R-matrix calculations. We find a proton partial width for this state in agreement with Utku et al [19], but a significantly narrower alpha width, and consequently a total width which is less than was found by Dalouzy et al [6].…”

“…Based on two previous observations of a state with likely J π = 3/2 + approximately 100 keV higher in energy [6,19], we have included resonance D to our R-matrix calculations. We find a proton partial width for this state in agreement with Utku et al [19], but a significantly narrower alpha width, and consequently a total width which is less than was found by Dalouzy et al [6]. It seems likely therefore that features C and D are poorly resolved in this and other measurements, with both states having proton widths of order 1-3 keV and the sum of their alpha widths being of order 40-50 keV (assuming their spins are as stated).…”

“…The Generator Coordinate Method model that made this prediction also suggests the existence of another broad 1/2 + state (Γ p = 157 keV, Γ α = 139 keV) at a resonance energy around 1.49 MeV (E x ( 19 Ne) = 7894 keV). Data from a recent 1 H( 19 Ne,p) 19 Ne * (p) 18 F inelastic scattering measurement revealed a broad feature beneath several well defined peaks that is consistent with the presence of such a state [6]. However, a direct measurement using the thick target method [7] revealed no such feature, though a narrow state of different spin was observed in the vicinity.…”