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Title: Energy-loss straggling of helium projectiles at low kinetic energies

Abstract

Concentration depth profiles at liquid surfaces can be determined by means of neutral impact collision ion scattering spectroscopy. The energy resolution of the spectra is influenced by the energy loss straggling of the projectiles. Energy loss straggling is a measure of the width of the energy loss distribution of particles passing through matter. Knowledge of the energy loss straggling is especially important for determining concentration depth profiles of aqueous surfaces. Here it is shown that the energy loss in the gas phase and the energy loss distribution can be determined with a series of spectra taken at different vapor pressures of the aqueous solution. The projectiles used are 3 keV helium ions. The gas phase causes a shift of the spectra to lower energies and a broadening of the structure due to energy loss straggling. Both the energy loss in the gas phase and the energy loss straggling must be gauged in order to determine concentration depth profiles quantitatively. Knowledge of the energy loss distribution can be used to determine accurate concentration depth profiles by means of deconvolution.

Authors:
 [1]
  1. Wilhelm-Ostwald-Institute for Physical and Theoretical Chemistry, Leipzig University, Linnestrasse 3, 04103 Leipzig (Germany)
Publication Date:
OSTI Identifier:
20982346
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. A; Journal Volume: 75; Journal Issue: 3; Other Information: DOI: 10.1103/PhysRevA.75.032901; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; AQUEOUS SOLUTIONS; COLLISIONS; DISTRIBUTION; ENERGY LOSSES; ENERGY RESOLUTION; HELIUM; HELIUM IONS; KEV RANGE 01-10; KINETIC ENERGY; LIQUIDS; SCATTERING; SPECTRA; SPECTRAL SHIFT; SPECTROSCOPY; SURFACES; VAPOR PRESSURE

Citation Formats

Andersson, Gunther. Energy-loss straggling of helium projectiles at low kinetic energies. United States: N. p., 2007. Web. doi:10.1103/PHYSREVA.75.032901.
Andersson, Gunther. Energy-loss straggling of helium projectiles at low kinetic energies. United States. doi:10.1103/PHYSREVA.75.032901.
Andersson, Gunther. Thu . "Energy-loss straggling of helium projectiles at low kinetic energies". United States. doi:10.1103/PHYSREVA.75.032901.
@article{osti_20982346,
title = {Energy-loss straggling of helium projectiles at low kinetic energies},
author = {Andersson, Gunther},
abstractNote = {Concentration depth profiles at liquid surfaces can be determined by means of neutral impact collision ion scattering spectroscopy. The energy resolution of the spectra is influenced by the energy loss straggling of the projectiles. Energy loss straggling is a measure of the width of the energy loss distribution of particles passing through matter. Knowledge of the energy loss straggling is especially important for determining concentration depth profiles of aqueous surfaces. Here it is shown that the energy loss in the gas phase and the energy loss distribution can be determined with a series of spectra taken at different vapor pressures of the aqueous solution. The projectiles used are 3 keV helium ions. The gas phase causes a shift of the spectra to lower energies and a broadening of the structure due to energy loss straggling. Both the energy loss in the gas phase and the energy loss straggling must be gauged in order to determine concentration depth profiles quantitatively. Knowledge of the energy loss distribution can be used to determine accurate concentration depth profiles by means of deconvolution.},
doi = {10.1103/PHYSREVA.75.032901},
journal = {Physical Review. A},
number = 3,
volume = 75,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
  • Absolute measurements of stopping powers and energy straggling for hydrogen- and helium-ion beams in Ge, Se, Pd, Ag, Sb, and Bi in the energy range 20 < or = E < or = 260 keV were performed by the method of determining the energy loss suffered by an ion beam which has traversed a thin film. The measured stopping powers fit reasonably well with those of other authors obtained at higher and lower ion energies. Agreement with theoretical predictions for energies >100 keV/amu is found to be better for hydrogen than it is for helium beams. The Z/sub 2/ dependencemore » of the stopping power for hydrogen projectiles is discussed including measurements of other authors performed on other elements, and is found to agree in shape with that for helium for ion velocities v > 2 a.u., but there is evidence that it begins to differ with decreasing v. It is deduced from the present measurements that for hydrogen as well as helium ions the amplitude of oscillations of the Z/sub 2/ dependence increases with decreasing ion velocity, reaching a maximum at v = 1.4 a.u. The Lindhard-Scharff theory is found to be in satisfactory agreement with the measured energy straggling.« less
  • Based on the dielectric-function method, we have investigated the energy loss and straggling of heavy atoms with atomic number {ital Z}{sub 1} passing through the degenerate electron gas at low velocities. The size parameter {Lambda} of the electron cloud on the projectile is newly determined according to the statistical variational method by taking into account the static screening effect of conduction electrons. The analytical formulas obtained here have {ital Z}{sub 1} dependences different from those of existing theories in spite of the same velocity dependence. It is found that the screening effect on {Lambda} enlarges the electronic stopping of themore » media by a constant value regardless of {ital Z}{sub 1}. Numerical results show agreement with the trends of the available data.« less
  • The energy-loss straggling of protons channeled in gold crystals in the <100> direction has been experimentally and theoretically studied at the low-velocity limit. The experimental results show a threshold effect in the straggling values, which is similar to that observed earlier in the energy loss. This effect is described by a theoretical model which explains the velocity dependence by considering the individual features of the contributions of free electrons in the conduction band and the nearly free (5d{sup 10}) electrons which generate a threshold effect at low energies due to their binding energy. The model predicts a deviation of proportionalitymore » with ion velocity of the energy-loss spread and yields a good description of the obtained experimental data.« less