We report electron scattering form factors for known 4 states in ' 0 at 17.79 and 18.98 MeV.We also report statistical upper bounds for the 4 state at 19.80 MeV. The ratios of these form factors are consistent with the isospin amplitudes derived from pion scattering data. The form factors of levels observed in (e, e') at 17.880+0.015, 18.635+0.020, and 20. 510+0.025 MeV are compatible with 4 T =1 assignments. Existing (n, m') and (p, p') spectra do not contradict these identifications.The 4 form factors are well described by a harmonic-oscillator density with oscillator length b =1.58 fm. This value is substantially smaller than the value of 1.77 fm obtained from the ground state charge density. The form factor of the 18.98 MeV state can also be fitted by a Woods-Saxon transition density, with parameters fitted to the elastic M5 multipole of "O. The fit is improved by inclusion of meson-exchange currents. However, the isoscalar-isovector differences in the WoodsSaxon plus meson-exchange current form factors result in a poor fit to the 17.79 MeV state. The total isovector and isoscalar strengths observed for the established 4 states are 41% and 23%, respectively, of a pure single-particle prediction.

No abstract

at excitation energies between 1S and 23 MeV. Measurements were performed at 90' for momentum transfers of 1.4, 1.S, 1.7, and 1.9 fm ' and at 160' for a momentum transfer of 1.7 fm '. Several prominent narrow peaks were observed in the spectra of both nuclei. The measured form factors for levels in '~O at 1S.78, 17.06, 20.14, and 20.70 MeV and in "0 at 18.70, 20.36, and 22.39 MeV are, within experimental uncertainties, completely transverse. These strongly excited states are assumed to arise from isovector M4 transitions of the type 1@3&2~1d5q2. A simple weak-coup1ing model is used to assign spins to the levels in ' O. Finally, we also report measurements for several narrow states in both nuclei, for which the spins and parities have not yet been identified.

Form-factor measurements in the momentum-transfer range 0.6~q~2. 7 fm ' are presented for the 1 levels in ' 0 at 4.46, 6.20, 7.62, and 8.04 MeV, the 3 levels at 5.10, 6.40, and 8.29 MeV, and the 5 levels at 7.86 and 8.13 MeV. These are the first measurements of the 5 states by inelastic scattering and the first electron-scattering measurements of the higher 1 and 3 states. A Rosenbluth separation of the longitudinal and transverse form factors was performed by fitting the data with a phenomenological polynomial-times-Gaussian parametrization motivated by the form of theoretical form factors when harmonic-oscillator wave functions are used. Comparisons are made with structure models. The Coulomb form factors of several levels indicate the significance of small admixtures of 3Am components in the negative-parity wave functions.