113 research outputs found

    Plasmons in Scanning Transmission Electron Microscopy Electron Spectra

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    A general self-energy formulation of the interaction between an electron in a scanning transmission electron microscope (STEM) and a localized target is given. We prove a theorem relating the probability of energy transfer to that calculated classically. Local dielectric theory of target excitation for various geometries is discussed. The problem of localization of initially unlocalized excitations in the valence band of solids is treated by transforming cross sections differential in momentum transfer into dependence on an impact parameter variable. We are thereby able to account for experimental data in scanning electron microscopy (SEM) that show high spatial resolution

    Dicluster Stopping in a Degenerate Electron Gas

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    In this paper we report on our theoretical studies of various aspects of the correlated stopping power of two point-like ions (a dicluster) moving in close but variable vicinity of each other in some metallic target materials the latter being modelled by a degenerate electron gas with appropriate densities. Within the linear response theory we have made a comprehensive investigation of correlated stopping power, vicinage function and related quantities for a diproton cluster in two metallic targets, aluminum and copper, and present detailed and comparative results for three approximations to the electron gas dielectric function, namely the plasmon-pole approximation without and with dispersion as well as with the random phase approximation. The results are also compared, wherever applicable, with those for an individual projectile.Comment: 29 figures, LaTe

    Antiproton stopping power in hydrogen below 120 keV and the Barkas effect

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    The simultaneous measurement of the spatial coordinates and times of p¯s annihilating at rest in a H2 target at very low density ρ (ρ/ρ0<10-2, ρ0 being the STP density) gives the possibility of evaluating the behavior of the p¯ stopping power in H2 at low energies (below 120 keV). It is different from that of protons (the Barkas effect). Moreover, it is shown that a rise at low-energy values (≲1 keV) is needed to agree with experimental data
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