High Quality Content by WIKIPEDIA articles! High Quality Content by WIKIPEDIA articles!Helium atom scattering (HAS) is a surface analysis technique used in materials science. HAS provides information about the surface structure and lattice dynamics of a material by measuring the diffracted atoms from a monochromatic helium beam incident on the sample.The first recorded He diffraction experiment was completed in 1930 by Estermann and Stern on the (100) crystal face of lithium fluoride. This experimentally established the feasibility of atom diffraction when the de Broglie wavelength, ?, of the impinging atoms is on the order of the interatomic spacing of the material. At the time, the major limit to the experimental resolution of this method was due to the large velocity spread of the helium beam. It wasn't until the development of high pressure nozzle sources capable of producing intense and strongly monochromatic beams in the 1970's that HAS gained popularity for probing surface structure. Interest in studying the collision of rarefied gases with solid surfaces was helped by a connection with aeronautics and space problems of the time.

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