Electron scattering studies of 20Ne and 3He isotopes

The method of electron scattering was used to study the giant resonance excitations of 20Ne and the rms charge radius of 3He. All data were collected at the 140 MeV linear electron accelerator facility at the National Bureau of Standards, Washington, D.C. Electrons with incident energies of 59.5, 89.7, 119.6 MeV were observed at an angle of 750, and an incident energy of 84.7 MeV were observed at an angle of 127.50 after scattering from 20Ne. The two measurements at 84.7 MeV and 127.50, and 119.6 MeV and 750, constituted a matching momentum transfer pair which was used for separating the form factor squared into longitudinal and transverse components. The target gas was contained in a 350 cm3 sealed rectangular gas cell pressurized to about ten atmospheres above vacuum. Well defined resonances of E2 transition character were observed at excitation energies of 12.8, 13.5, 14.0, 14.7, 15.3, and 16.5 MeV. The sum of strengths of these resonances was found to exhaust about 30% of the energy weighted sum rule with estimated uncertainty of about 15%. Also a broad E2 structure is observed centered around 21 MeV excitation energy whose strength was estimated to be less than 57% of the energy weighted sum rule with estimated uncertainty of about 20%. Electrons were scattered elastically from an accurately known mixture of 3He and CH4 gases contained in a 350 cm3 sealed rectangular gas cell pressurized to about three atmospheres above vacuum. Cross sections of 3He relative to 12C were measured in the range of momentum transfer squared between 0.032 and 0.34 fm-2 with an incident energy resolution of about 0.2%. The 3He rms charge radius was found to be 1.902 +- 0.047 fm