Electroexcitation of isoscalar states insup16O

We report high resolution measurements of inelastic electron scattering to all narrow normal-parity states of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ up to 12.05 MeV, which include states with $J_n^{\pi }$($E_x$ MeV): $0_2^{+}$(6.049), $0_3^{+}$(12.049), $1_1^{\mathrm{-}}$(7.117), $2_1^{+}$(6.917), $2_2^{+}$(9.845), $2_3^{+}$(11.52), $3_1^{\mathrm{-}}$(6.130), $4_1^{+}$(10.356), and $4_2^{+}$(11.097). The measurements were performed primarily at 90° and 160° and span momentum transfers between 0.6 and 2.6 ${\mathrm{fm}}^{\mathrm{-}1}$. Improved line shape fitting techniques have been developed. These are the first electron scattering measurements for the $4_2^{+}$ state and of second form-factor maxima for several states. The form factor for excitation of the $2_2^{+}$ state is strikingly different from that of the other $2^{+}$ states and indicates a transition density peaked in the interior. Transition charge densities were extracted from a combined data set that includes earlier electron scattering data renormalized to a recent analysis of elastic scattering from ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. Comparisons have been made with several structure models, including the Brown-Green model, the weak-coupling model, a 2ħω shell model, and the tetrahedral alpha-cluster model.