CHANNELING OF MEV HE+ IONS IN TUNGSTEN AND OTHER CRYSTALS - AN INTERCOMPARISON OF RUTHERFORD SCATTERING AND OF CHARACTERISTIC L AND M X-RAY YIELDS

Measurements of wide-angle (150°) scattering and of L and M x-ray yields in tungsten single crystals are reported as a function of crystallographic orientation with respect to an incident beam of 1.4-MeV helium ions. Comparison of these yields establishes both lower and upper limits for the minimum impact parameter (rmin) between a channeled ion and the tungsten-lattice atoms; these limits are consistent with Lindhard's estimate that rmin a, the Thomas-Fermi screening distance (i.e.,0.11 for He in W). A similar comparison between wide-angle scattering and x-ray yield curves is reported for several other lattices Al, Si, GaP, GaSb, and UO2; again the results are consistent with the predicted relationship: rmin a. Anomalies in published orientation studies of K, L, and M x-ray yields are shown to be due to depth effects. © 1969 The American Physical Society.