A confirmative spin-parity assignment for the key 6.15 MeV state in $^{18}$Ne of astrophysical importance

TL;DR

This study confirms the spin-parity of the 6.15 MeV state in $^{18}$Ne as 1$^-$, crucial for astrophysical reaction rates, using resonant elastic scattering and R-matrix analysis, and reports a new 6.85 MeV state.

Contribution

The paper provides the first firm spin-parity assignment for the 6.15 MeV state in $^{18}$Ne and identifies a new excited state at 6.85 MeV, advancing understanding of astrophysical reaction pathways.

Findings

Confirmed 6.15 MeV state as 1$^-$ in $^{18}$Ne

Identified a new 6.85 MeV excited state

Implications for astrophysical reaction rates

Abstract

Proton resonant states in $^{18}$Ne have been investigated by the resonant elastic scattering of $^{17}$F+$p$. The $^{17}$F beam was separated by the CNS radioactive ion beam separator (CRIB), and bombarded a thick H$_2$ gas target at 3.6 MeV/nucleon. The recoiled light particles were measured by using three sets of ${\Delta}$E-E Si telescope at scattering angles of $\theta$$_{lab}$$\approx 3^\circ$, 10$^\circ$ and 18$^\circ$, respectively. Four resonances, {\it i.e.}, at $E_{x}$=6.15, 6.30, 6.85, and 7.05 MeV, were observed clearly. By $R$-matrix analysis of the excitation functions, $J^{\pi}$=1$^-$ was firmly assigned to the 6.15 MeV state which is a key state in calculating the reaction rate of $^{14}$O($\alpha$,$p$)$^{17}$F reaction. This reaction was thought to be one of the most probable key reactions for the breakout from the hot-CNO cycle to the $rp$-process in type I x-ray bursts In addition, a new excited state observed at $E_{x}$=6.85 MeV was tentatively assigned as 0$^{-}$, which could be the analog state of 6.880 MeV, 0$^{-}$ in mirror $^{18}$O.