DECHANNELING BY IONIZED POINT-DEFECTS IN SOLIDS - DOUBLE SCREENING EFFECTS

The interaction between an external probe particle and host lattice is described by a screened Coulomb potential which gets modified due to the presence of impurities in the lattice. A double screened potential was earlier derived and we extend the formulation to include higher o rder terms in the dielectric function epsilon(q) which defines the scr eening parameters of this potential. The weakly decaying nature of the potential thus derived manifests itself in dechanneling process and s cattering cross-section. It will also be evident from this formulation that the conduction electrons of the host lattice play an important r ole in the interaction between the probe particle and impurities. Dech anneling cross-sections are modified for various charge states of impu rity in different planar directions when we consider the effect of bot h atomic electrons of the impurity and conduction electrons of the hos t lattice. The results for alpha-particle dechanneling in palladium (b y C or H impurities) and for muon dechanneling by oxygen in tantalum a re compared with earlier calculations and available experimental resul ts.