Diffraction of Slow Positive Ions

AN experimental method has been developed which permits photographic recording of the scattering of slow positive ions through angles of a fraction of a degree. This is accomplished by using a very fine, electrostatically focused incident beam and accelerating the ions, after the scattering, to a velocity high enough to affect a photographic plate. The high-voltage electrostatic lens used to give the acceleration also produces an angular magnification of the scattered rays.