New direct observation data on the 2 s -2 p atomic state coherent mixing upon hydrogen atoms passage through a metal-wall slit are presented. The experimental results are interpreted in terms of atomic state interference, the state mixing amplitude being derived directly from the experimental data obtained.
The interference of the 2 P state of the hydrogen atom due to unknown long-range interaction with the metal surface (Sokolov effect) has been studied by an atomic interferometer. In contrast to previous experiments, where an atomic beam passed through slits in metal plates, a beam in the presented experiments passes at a given distance from the edges of the plates. It has been found that the interference is clearly observed if two plates are located on the same side of the beam. However, this interference disappears if one plate is displaced to the opposite side. This result cannot be explained in the framework of the available hypotheses on the nature of the effect under investigation.
An expression is given for the Stark-induced beat signal in the Lyman-$\ensuremath{\alpha}$ radiation from hydrogen atoms in a beam-foil experiment. This expression includes possible contributions to the beat signal from coherent excitation of S and P states in the beam-foil process. For the case where the electric field is applied parallel to the beam, the coherentexcitation contributions can be separated experimentally from those resulting purely from coherence produced by the electric field, by simply reversing the direction of the electric field.