INELASTIC ELECTRON SCATTERING FROM 4HE

The spectra of electrons scattered inelastically from 4He have been measured at incident energies from 150 MeV to 400 MeV for scattering angles from 38° to 90°. Through the use of a liquid 4He target, a high momentum resolution (≈0.25%) was obtained, and the 20 MeV 0+ state of the α-particle was observed for the first time in electron scattering. The excitation energy and the total width of this state were determined and are in good agreement with the results from other experimental methods. It was found that the total disintegration cross section appears be smaller than 2(σp+σn) by more than an order of magnitude at the lowest q2(≈ 0.33 fm-2). In earlier work the assumption of a total cross section of 2(σp+σn) was found to be quite accurate for higher q2. As a new result, the partial radiative width for the 0+ state is determined to be Γrad = 1.1±0.3 meV. © 1968.