Neutral atom and molecule focusing using a Fresnel zone plate

摘要

Focusing of neutral atoms and molecules has several potential applications. The very first microscopy images using helium as an imaging probe were published earlier this year. Anotherpossible application is to study the diffusion of atoms and molecules through materials with highspatial resolution by stepping a porous or permeable sample across the focused beam. With thisapplication in mind, the authors present the best resolution transmission images hitherto achievedwith helium atoms less than 2 m of a thin carbon film with 2 m holes. Furthermore, theypresent the first experiment using a Fresnel zone plate to focus neutral molecules. They used a beamof deuterium D2 which was focused down to 15.2 0.5 m. D2 was chosen because it fits in massto the geometry of our system, which is optimized for helium. However, the method can be extendedto hydrogen H2 or other molecules by using a suitably adapted zone plate. In both cases the focuswas limited by chromatic aberrations, caused by the velocity spread of the beams. Finally, theypresent calculations exploring the resolution limits for focusing of molecular beams using Fresnelzone plates. The calculations show that Fresnel focusing down to 170 nm full width at halfmaximum is possible with presently available techniques.