Helium beam moves into sharper focus
Dec 3, 1999
A team of German physicists has taken an important step in the development of an atomic de Broglie microscope. Led by Peter Toennies of the Max Planck Institute for Fluid Dynamics in Göttingen, Germany, the group has found a way to focus a beam of neutral helium-4 atoms by exploiting the atoms' wave-particle duality. The smaller de Broglie wavelength of helium atoms allows for higher resolution images than is possible with conventional electron or photon based microscopes. A helium beam would be non-penetrating, chemically inert and produce no mechanical damage, making it easier to image biological samples. (Phys. Rev. Lett. 83 4229).
Physicists have tried for years to develop a beam of atoms that could be focused as easily as electrons and photons. The helium atoms are fired at 1 km/s through a micron diameter nozzle past a set of fresnel plates - concentric rings of material of varying thickness. As the beam passes the plates, the wave patterns of the atoms interfere with one another, focusing the beam to a spot 2 micrometers wide. As well as being 10 times narrower than previous atom beams, such a beam is also 1000 times more intense, and 100 million times more dense. The researchers hope that by using a smaller nozzle they should be able to focus the beam to submicron levels.