Quantum models for dechanneling by point defects and extended defects

A quantum mechanical description of dechanneling by point defects will be presented. The effects of electrons of heavy impurities and those of host material are treated in a double screening formulation. For extended defects like stacking faults and dislocations, a sudden approximation model is used. For positively charged channeled particles, the transition among bound states in the simple harmonic type transverse potential, induced by the sudden appearance of the extended defect (stacking fault or distortion due to dislocation) are considered. The resulting dechanneling probabilities and their energy dependences are calculated. An extension of the model to relax the sudden approximation (specially for dislocations) in a time dependent formulation has also been outlined and main results presented. (author)