Lifetime of the21+state and densities for the0g.s.+→21+transition inNe18

We report a measurement of the lifetime of the ${2}_{1}^{+}$ state in $^{18}\mathrm{Ne}$ using the Doppler shift attenuation method, the $^{3}\mathrm{He}(^{16}\mathrm{O},n)$ reaction, and large volume germanium $\ensuremath{\gamma}$-ray detectors of the ``clover'' design. The present measurement gives a $B(E2;{0}_{\mathrm{g}.\mathrm{s}.}^{+}\ensuremath{\rightarrow}{2}_{1}^{+})$ value somewhat lower than that obtained in a previous measurement more than 25 years ago made using the same technique but with a smaller volume germanium detector. In addition, we report a semimicroscopic reanalysis of recent $^{18}\mathrm{Ne}+^{197}\mathrm{Au}$ data on the ${0}_{\text{g.s.}}^{+}\ensuremath{\rightarrow}{2}_{1}^{+}$ transition in $^{18}\mathrm{Ne}$ and compare the $B(E2;{0}_{\text{g.s.}}^{+}\ensuremath{\rightarrow}{2}_{1}^{+})$ results obtained using the two experimental techniques. The comparison between the two methods demonstrates the need for a basis for setting the imaginary part of the optical model potential in the analysis of the scattering experiment before reliable $B(E2;{0}_{\text{g.s.}}^{+}\ensuremath{\rightarrow}{2}_{1}^{+})$ values can be extracted by inelastic scattering when nuclear scattering contributions are significant. The optical model potential could be fixed via a detailed elastic scattering measurement.