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The basic concepts of both classical and quantum mechanical theories of channeling radiation are presented. The theories developed are discussed separately in low, medium and high energy regions. [ABSTRACT FROM PUBLISHER]

A model for calculation of helium stopping powers is developed which takes into account different charge fraction contributions. The neutral part contribution is treated according to the ordinary Firsov theory, whereas for the charged part of the ion beam earlier classical stopping power calculations for point charges by Kührt and Wedell are used. [ABSTRACT FROM PUBLISHER]

A dechanneling model for axially channeled electrons in a single string approximation is proposed. Consideration is given to dechanneling due to multiple scattering by the atomic string electrons and by the thermal vibrations of nuclei. The model has been used to calculate the electron dechanneling length as a function of injection angle θ relative to the tungsten atomic string ⟨111⟩ at an electron energy of 1 GeV. [ABSTRACT FROM PUBLISHER]

By using the solution of the Fokker-Planck-equation a backscattering spectrum from small depths was calculated. A comparison with the experimental results by Van der Weg et al. for 130 keV protons channelled in the (110)-direction of silicon shows a good agreement. [ABSTRACT FROM PUBLISHER]

Measurements of Xe(M)-radiation induced by Xe-ion bombardment of copper crystals were camcd out for the energy-range 80-200 keV. In the case of unimplanted copper targets the x-ray yields in low indicated directions have minima, whereas for Xe-implanted copper targets in the same directions at an energy of the order of 140 keV appear maxima, which increase with decreasing bombardment energy. It was shown that these enhancements are caused not by the flux-peaking effect of orientation department enrichment of Xe-ions in copper crystals, but by the angular dependence of the stopping power of Xe-ions under Channelling conditions. Calculations of the angular dependence of the x-ray yield are carried out by means of a theoretical model, which takes into account flux distribution and energy losses of Xe-ions in copper crystals. The calculated results are in good agreement with the measurements. [ABSTRACT FROM PUBLISHER]

A calculation of the spatial and angular distributions in planar channelling of particles is made on the basis of solution of the Fokker-Planck equation. The analytical formulae for these distributions are derived with allowance for multiple scattering by electrons. The dynamics of establishing equilibrium in the momentum and configurational spaces was investigated in detail. It is shown that in the momentum space the equilibrium was reached later than in the configurational space. [ABSTRACT FROM PUBLISHER]

The theory of relativistic electron and positron bremsstrahlung depending on the impact parameter has been developed on the basis of the virtual photon method. This theory is used to calculate bremsstrahlung under channelling conditions. Common bremsstrahlung turned out to be suppressed in the case of relativistic positron channelling. The main mechanism of stopping is, here, the common bremsstrahlung by valence electrons and a specific radiation of channelled positrons considered recently by Kumakhov. Since energy losses connected with the radiation are (two to three) orders smaller than losses of bremsstrahlung in amorphous medium, our theory predicts an anomalous decrease of energy losses of channelled relativistic positrons. Estimates of the bremsstrahlung of electrons under channelling conditions show an increasing yield compared with the random yield that coincides with experimental results. An analysis has been made of physical differences between the Kumakhov radiation and coherent bremsstrahlung. The optimum conditions for observing the Kumakhov radiation have been found. [ABSTRACT FROM PUBLISHER]

The paper presents an approximate solution of the Focker-Planck kinetic equation with an allowance for the unharmonic potential. This solution is obtained by using asymptotic methods of non-linear mechanics. It is shown that the perturbation theory method is inapplicable for this problem. The solution obtained is used to calculate the relative flux in planar and axial channels. The theory developed in this paper may be used to interpret experiments on determining the location of an impurity atom in a lattice. [ABSTRACT FROM PUBLISHER]