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van der Waals transitions among magnetic sub-levels of a metastable rare gas atom passing near a surface immersed in a magnetic field, are described. Related transition amplitudes are calculated using both the sudden and the Landau-Zener approximations. Experimental data for Ne*(3P2) atoms traversing a copper grating are presented. For a pair of surfaces (e.g. the opposite edges of a slit) and a sufficiently large coherence width, Fresnel’s biprism interference fringes are obtained. From this interference pattern, detailed information about the transition amplitude at a sub-nanometric scale can be derived. The effect of gravity on this pattern is examined. [ABSTRACT FROM AUTHOR]

1D and 2D reflection gratings (Permalloy stripes or dots deposited on silicon), immersed in an external homogeneous static magnetic field, are used to study 1D and 2D diffraction of fast metastable helium atoms He* (23S1). Both the grazing incidence used here and the repulsive potential (for sub-level m = -1) generated by the magnetisation reduce the quenching effect. This periodically structured potential is responsible for the diffraction in the incidence plane as well as for the diffraction in the perpendicular plane. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]