RESONANCE AND INTERFERENCE PHENOMENA IN THE PHOTOIONIZATION OF A HYDROGEN-ATOM IN A UNIFORM ELECTRIC-FIELD .4. DIFFERENTIAL CROSS-SECTIONS

The differential cross section for the photoionization of an atom in a uniform electric field can be observed if the photocurrent is registered on the plane screen perpendicular to the uniform field axis. In the photodetachment case the differential cross section structure is interpreted exclusively in terms of the interference between two photoelectron classical trajectories passing through a given point on the screen. When the photoionization of the neutral atom is considered the resonance effects should be taken into account. If the photon energy is chosen so that the photoionization proceeds into a particular resonance state then the differential cross section represents essentially the squared resonance wavefunction in the parabolic coordinate xi. Generally, together with the resonance contribution some background term also exists which is analysed using Watson transformation of the partial cross section sum. Various types of structure appear in the background term depending on the photoelectron energy and the region of the screen. They are interpreted in terms of electron trajectories (glory- and rainbow-type contributions). The constant magnetic field applied perpendicular to the electric field distorts the cross section pattern due to the Aharonov-Bohm effect. Some tentative applications of the differential cross section study are discussed, such as measurement of the ionization potentials (or electron affinities) and observation of weak magnetic fields. © 1990, IOP Publishing Ltd.