Photodetachment microscopy of O-

Photodetachment of O- ions is performed in the presence of a static electri c field. A high spatial resolution electron detector is used to map out the ejected electron's wave function. Propagation over half a metre does not a lter the stationary structure the electron wave possesses in the direction orthogonal to the detachment motion. Nodes and antinodes of electron curren t density are observed, that can be interpreted as direct imaging of the in ternal atomic wale function. Because detachment of a negative ion can be re presented accurately in the free-electron approximation, the obtained image s can also be viewed as direct experimental representations of the Green fu nction of the uniform acceleration problem. Agreement of the measured distr ibutions with the exact expression of this wave-function appears quite sati sfactory.