Observation of the Astrophysically Important3+State inN18evia Elastic Scattering of a RadioactiveF17Beam fromH1

Abstract

The ${}^{17}\mathrm{F}(p,\gamma {)}^{18}\mathrm{Ne}$ reaction is important in stellar explosions, but its rate has been uncertain because of an expected $3^{+}$ state in ${}^{18}\mathrm{Ne}$ that has never been conclusively observed. This state would provide a strong $\ell =0\mathrm{}$ resonance and, depending on its excitation energy, could dominate the stellar reaction rate. We have observed this missing $3^{+}$ state by measuring the ${}^1\mathrm{H}{(}^{17}\mathrm{F},p{)}^{17}\mathrm{F}$ excitation function with a radioactive ${}^{17}\mathrm{F}$ beam at the ORNL Holifield Radioactive Ion Beam Facility. We find that the state lies at a center-of-mass energy of $E_r=599.8\mathrm{}\pm 1{.5}_{\mathrm{stat}}\pm {2.0}_{\mathrm{sys}}\mathrm{keV}$ ( $E_x=4523.7\mathrm{}\pm 2.9\mathrm{keV}$) and has a width of $\Gamma =18\mathrm{}\pm 2_{\mathrm{stat}}\pm 1_{\mathrm{sys}}\mathrm{keV}$.