Spin alignment following inelastic scattering of 17Ne, lifetime of 16F, and its constraint on the continuum coupling strength

The sequential two-proton decay of the second excited state in Ne-17, 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 F-16, to be determined from the magnitude of the final-state interactions between the protons. This new method gave a result [Gamma = 20.6(57) keV] consistent with that obtained by directly measuring the width of the state [Gamma = 21.3(51) keV]. This width allows one to determine the continuum coupling constant in this mass region. Real-energy continuumshell-model studies yield a satisfactory description of both spectra and widths of low-energy resonances in F-16 and suggest an unusual large ratio of proton-proton to proton-neutron continuum couplings in the vicinity of the proton drip line.