Recapture of particles into channeling

The motion of negatively charged channeled particles along atomic planes in crystals and the specular reflection of positively charged particles from smooth amorphous or polycrystalline films are investigated theoretically. The use of stacks of suitably curved crystals to recapture negative particles from quasi-dechanneled states and of capillary-tube arrays to spread or focus beams of positively charged particles is proposed and illustrated with drawings, and applications to the design of ion optics are indicated.