THE CHANNELING OF ENERGETIC ATOMS IN CRYSTAL LATTICES
Preliminary studies showed that approximates - 1% of 10-kev Cu atoms, starting from lattice sites and slowing down according to the Bohr potential, made very long flights, predominantly in (110) directions. These channeled particies did not move in force-free regions but experienced very many glancing collisions with atoms of the lattice, which steered them into (110) directions. This phenomenon of channeling so dominates the Bohr potential calculations for particles normally incident upon the low index planes of Cu that no reliable statistical inferences about range distributions can be drawn. The probability of channeling increases rapidly with increasing energy for particles incident upon (110) and (100) from energies below 1 kev and for particles incident upon (111) from about 3 kev. In each case, the preferred channel is normal to the crystal surface. In the isotropic case, the probability of channeling remains roughiy constant at about 1% between 1 and 10 kev, the (110) channels being strongly preferred. Channeling is not restricted to fcc crystals. Calculations for diamond and bcc structures al4o show extensive channeling. The existence of channeling may have significant implications for radiation damage theory, since the channeled particies lose their energy in very small increments, thus producing far fewer displacements than would be expected on the basis of conventional cascade theory. (C.E.S.) The hamiltonian of a system of charged particles interacting with the electromagnetic field is investigated. For an arbitrary system the multipole expansion of the interaction between the system and the field is derived by means of a suitable canonical transformation. The transformed hamiltonian is obtained from the hamiltonian of the system by replacing the momenta by the transformed kinetic momenta and by addirg to the hamiltonian a term representing the interaction of the system with the eiectric component of the field. By expanding this interaction term, as weli as the transformed momenta, in powers of the dimension of the system over the wavelength, the multipole expansion of the hamiltonian is obtained. For a system interacting with a classical field the muitipole form of the hamiltonian is exactly equivalent to the originai hamiltonian. For a quantized field this is not true, and the multipole form of the transformed hamiltonian is shown to be equivalent to the original hamiitonian oniy for first-order radiation processes. (auth)
- Research Organization:
- Oak Ridge National Lab., Tenn.
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-17-011348
- OSTI ID:
- 4726241
- Journal Information:
- Appl. Phys. Letters, Vol. Vol: 2; Other Information: Orig. Receipt Date: 31-DEC-63
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
Similar Records
Canonical transformations relating the oscillator and Coulomb problems and their relevance for collective motions
I. THEORY OF PARTICLES WITH ARBITRARY SPIN. II. PHOTOPRODUCTION OF Tm$sup 173$. Thesis