Spin alignment following inelastic scattering of Ne17 , lifetime of F16 , and its constraint on the continuum coupling strength

Abstract

The sequential two-proton decay of the second excited state in ${}^{17}\mathrm{Ne}$, produced by inelastic excitation at intermediate energy, is studied. This state is found to be highly spin aligned, providing another example of a recently discovered alignment mechanism. The fortuitous condition that the second decay step is slightly more energetic than the first, permits the lifetime of the one-proton daughter, the ground state of ${}^{16}\mathrm{F}$, to be determined from the magnitude of the final-state interactions between the protons. This new method gave a result [$\mathrm{\Gamma }=20.6\left(57\right)$ keV] consistent with that obtained by directly measuring the width of the state [$\mathrm{\Gamma }=21.3\left(51\right)$ keV]. This width allows one to determine the continuum coupling constant in this mass region. Real-energy continuum-shell-model studies yield a satisfactory description of both spectra and widths of low-energy resonances in ${}^{16}\mathrm{F}$ and suggest an unusual large ratio of proton-proton to proton-neutron continuum couplings in the vicinity of the proton drip line.