No abstract available

No abstract available

[en] A theory recently developed by the authors for slow and fast electrons is shown to be also applicable to channeled ions and to explain the experimental results about electron loss phenomena as a whole. The theory is based on the fundamental hypothesis of the nonadiabaticity of the ion-target interactions. How essential an exponential form of the interaction pseudo-potential is in explaining the energy exchange mechanism at the walls may be deduced from a quasi-classical development of the quantum model. The theory also allows a number of new experiments to be envisaged in the field of surface electron states

[en] In this letter a simple procedure for calculating the initial dechanneling of ions is presented. The calculations show good agreement with both experimental data and computer simulation data on planar dechanneling. (author)

[en] The MARLOWE program was used to study the statistics of sputtering on the example of 1- to 100-keV Au atoms normally incident on static (001) and (111) Au crystals. The yield of sputtered atoms was examined as a function of the impact point of the incident particles (''ions'') on the target surfaces. There were variations on two scales. The effects of the axial and planar channeling of the ions could be traced, the details depending on the orientation of the target and the energies of the ions. Locally, the sputtering yield was very sensitive to the impact point, small changes in position often producing large changes yield. Results indicate strongly that the sputtering yield is a random (''chaotic'') function of the impact point

[en] Ion channeling along the [001] direction in high-quality single crystals of (Y/Er)Ba₂Cu₃O_7-x revealed an abrupt change in displace-ments in the a-b plane of the Cu and O atoms at the superconducting transition, T_c; normal 'Debye-like' vibrations were found for the Y/Er and Ba atoms. The anomalous change in Cu-O displacements was found to shift directly with stoichiometry-induced changes in T_c, implying a direct link between the observed phonon anomaly and the superconducting transition. Recent measurements of ion-channeling along the [001] axis in (Bi_1.7Pb_0.3)Sr₂Ca₁Cu₂O_x single-crystals revealed a similar change at T_c, suggesting that this phonon anomaly is a general feature of high-T_c superconductivity. In order to identify more specifically the crystallographic directions and displacement amplitudes associated with the anomalous phonon behavior, axial channeling scans using RBS, as well as characteristic x-ray production, were taken at several temperatures between 30 and 300K along the [301] and [331] directions of YBa₂Cu₃O_7-x single crystals. Twins present in the specimens, and the existing static atomic displacements present along these directions, caused the channeling to be poorer along these axes compared to the (001) direction. Also, a much stronger dependence of the minimum yield on depth was observed. However, since only one twin variant generally dominated over sufficiently wide areas of the specimens, reasonably good (approx 10 percent) minimum yields could be obtained along the appropriate [331] axis, and detwinned crystals produced good results along [301]. (author). 27 refs.; 5 figs

[en] The first experimental mapping of ion beam channels near the Si <001> axis is reported. All features are identified by theoretical plots of silicon planar channels and axial channels

[en] This work is devoted to the construction of the universal axial (0 0 1) rainbow channeling proton-crystal interaction potential. It has been done by modifying the Moliere's interaction potential. We show that for very thin crystals with the cubic crystallographic structure, in the (0 0 1) orientation with respect to 2 MeV proton beams, it is possible to obtain a universal proton-crystal interaction potential from the morphological analysis of the rainbows in the proton transmission angular plane. © 2019

[en] Ion-implantation and ion-channeling measurements have been used to study deuterium (D) in silicon. The D was introduced at room temperature by implantation to 13 keV into single-crystal Si. The D was detected and its depth profile was measured by the D(³He, p)⁴He nuclear reaction, and simultaneously the Si lattice signal was obtained from the ³He backscattering. Comparisons of the observed channeling angular distributions with continuum-model calculated distributions for the <111>, <110>, and <100> axial and ]110] planar channeling directions indicate that the D is located predominantly in a single interstitial site 1.6 A along a <111> direction from a Si atom in the antibonding direction. The resulting structure is compared to other known impurity interstitial centers in Si and implications of this site are discussed

[en] Short communication; 1 ref