The proton stripping reaction ${}_{}{}^{17}{}_{}{}^{}\mathrm{He}$,d${)}^{18}$F has been used to reinvestigate the proton widths of the states in ${}_{}{}^{18}{}_{}{}^{}\mathrm{F}$ near the proton threshold. Distorted-wave angular distributions were calculated using appropriate methods for stripping to unbound states. The deduced proton width for the level at $E_x$=5.673 MeV ($J^{\pi }$${=1\mathrm{}}^{\mathrm{-}}$) is significantly larger than a previous value obtained from a direct radiative capture experiment. A subthreshold state at $E_x$=5.603 MeV ($J^{\pi }$${=1\mathrm{}}^{+}$) was found to have a rather large proton reduced width so that this state contributes significantly to the astrophysical S factor at low energy. These measurements lead to substantial changes in the stellar reaction rate for the ${}_{}{}^{17}{}_{}{}^{}(\mathit{p}$,α${)}^{14}$N reaction. This result is discussed in relation to recent observation of the isotopic abundance ratio ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${/}^{17}$O in red giant stars. In addition, the nuclear structure of ${}_{}{}^{18}{}_{}{}^{}\mathrm{F}$ is studied via the measurement of spectroscopic factors for most of the levels in ${}_{}{}^{18}{}_{}{}^{}\mathrm{F}$ bound against proton decay.

• Received 2 June 1989

DOI:https://doi.org/10.1103/PhysRevC.40.1972