Mechanism of the reaction sup 4 He( e , e prime d ) sup 2 H

The cross section for the {sup 4}He({ital e},{ital e}{prime}{ital d}){sup 2}H reaction has been measured as a function of the four-momentum transfer {ital q} at a missing momentum of 125 MeV/{ital c}. The data show that this reaction cannot be described as quasielastic knockout of a deuteron. In a microscopic description of the ({ital e},{ital e}{prime}{ital d}) cross section, assuming a direct knockout mechanism, the {ital q} dependence reflects the {ital p}-{ital n} relative wave function in {sup 4}He. However, even a calculation in this framework using a relativistic {sup 4}He wave function does not describe the data, indicating that other reaction mechanisms play a non-negligible role.