[en] We evaluate the magnitude of the difference in the electronic energy loss of positive muons and protons in solids in the low-energy range using both the dielectric formalism and the non-linear transport cross-section (TCS) method. The effects of mass increase at low energies, showing stopping differences between 5% and 1% for velocities in the range 0.2< v<1 a.u. We find that nuclear stopping effects must also be taken into account for a consistent analysis in the low-energy range

[en] The electronic energy loss for low velocity protons channeled in the <100> direction single crystal Au is calculated. The spatial distribution of valence electronic density in Au is calculated using Tight Binding Linear Muffin Tin Method. The proton trajectories are determined by numerical integration of the classical motion equation, and the energy loss is evaluated using the calculated valence electronic density in the friction term. The results allow to describe qualitatively the non linear behavior of energy loss with ion velocity observed experimentally. (author)

[en] Results for energy-loss straggling of protons and deuterons in channeling conditions in the low-velocity regime (v<1 a.u.) are presented. Energy loss distributions are obtained using a computer simulation code which is based on a semi-classical approach to determine the ion trajectories for ions channeled in Au<1 0 0>, the energy loss effects are taken into account by calculating the electronic excitations produced in the solid. We analyze the results obtained with and without threshold effects in the electronic energy loss, studying the dependence on foil thickness and mean particle energy inside the target. We find a good agreement of our results with earlier and more recent experimental data for protons in crystalline and polycrystalline gold targets

[en] We have developed avalanche photodiode (APD) arrays of the beveled edge type with high responsivity in the ultraviolet (UV) region. A 3x3 array with pixel size 3x3 mm² was made, in which the segmentation was done using selective diffusion in the front surface. This technique is an improvement over previous avalanche photodiodes, where the segmentation was done by cutting channels in the back of the detector. After the die was cut from the wafer, beveling and passivation was performed to avoid lateral surface breakdown. The quantum efficiency from 200 to 400 nm is close to 50%, which makes this detector suitable for Nuclear Spectroscopy applications using short wavelength scintillators. The gain and dark current coming from all pixels connected together, is similar to a single element detector with the same area, which indicates that the pixelization process does not reduce the performance compared to a detector without segmentation. We measured high crosstalk between adjacent pixels (20%) which indicates that the resistance between them is too low. Due to the high resistance, the noise in the pixels is also high, and the energy resolution from a ⁵⁷Co source is higher (36% FWHM) than previous arrays

[en] Experimental results on proton energy loss distributions obtained by ion transmission measurements in Pd polycrystalline thin films are reported. Deviations from the proportionality behavior of the energy loss as a function of the ion velocity is observed. These results are compared with similar measurements in Au. A theoretical model previously developed is used to explain the observed velocity dependence. General trends on the relationship between the electronic density of states of these metals and the non-proportionality of the energy loss with ion velocity are discussed

[en] The standard theory of multiple scattering of ions traversing matter assumes that the energy loss of a particle, during transit through a medium, is very small compared with its initial energy. Here we consider the effect of finite-energy losses on the multiple-scattering angular distributions, by taking into account the variation of the energy-dependent scattering cross section as a function of the depth penetrated into the material. The theory is generalized to account for a continuous slowing down of the beam particles. We study in particular, for the case of slow ions, the increased spread of the angular distributions due to the energy-loss effect

[en] Recent experimental determinations [J. E. Valdes, G. Martinez-Tamayo, G. H. Lantschner, J. C. Eckardt, and N. R. Arista, Nucl. Instrum. Methods B 73, 313 (1993)] of the energy loss of low-energy protons in Ag and Au show a departure from the velocity proportionality predicted by theory, while data for other metallic elements, such as Al, Sb, and Bi, are in agreement with this dependence. In this work we present measurements in Cu foils which show a similar behavior to that in Ag and Au. We give an interpretation of the differences between these cases due to the existence of small binding energies for the d electrons in Cu, Ag, and Au. We present a model based on transport cross section and density-functional theory, which introduces threshold effects in the calculation of the transport cross section of nonfree electrons, and explains the deviations from the velocity-proportional dependence

[en] The electronic energy loss for low-velocity protons channeled in the left-angle 100 right-angle direction of single-crystal Au is calculated. The spatial distribution of valence electronic density in Au is calculated by using the tight-binding linear muffin-tin method [O. K. Andersen and O. Jepsen, Phys. Rev. Lett. 53, 2571 (1984); O. K. Anderson, Z. Pawlowska, and O. Jepsen, Phys. Rev. B 34, 5253 (1986)]. The proton trajectories are determined by numerical integration of the classical equation of motion, and the energy loss is evaluated by using a quantum-mechanical transport cross-section approach with a self-consistent model based on Friedel close-quote s sum rule. The results allow us to describe the nonlinear behavior of energy loss with ion velocity observed experimentally. copyright 1996 The American Physical Society

[en] The energy loss of H⁺ ions in thin polycrystalline Al, Sb, Ag, Au and Bi films has been determined in the energy range below 10 keV. This low-energy range is of special interest to fill a lack of low-energy experimental data and test various theoretical predictions and semiempirical formulas. We find that the general theoretical prediction of a velocity-proportional dependence of energy loss does not hold for all targets studied in this work. The velocity-proportionality is better satisfied for Al, Sb and Bi, whereas a departure from such dependence is observed at lower energies for Ag and Au targets. The results obtained here are in good general agreement with nonlinear stopping power calculations based on density functional theory. Comparison with semiempirical predictions, and other experimental results are also done. (orig.)

[en] There are two different ways of measuring low energy ion scattering (LEIS), i.e. detection of ions and neutrals by means of time of flight (TOF-LEIS), or detection of ions only by means of an electrostatic analyser (ESA-LEIS). We discuss, how information on charge exchange can be extracted from ESA-LEIS and TOF-LEIS spectra, respectively and which is the level of accuracy that can be expected from these procedures