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1.
We describe the first calculation of the stopping power of an electron gas for slow ions using the density-functional formalism. We evaluate the nonlinear self-consistent potential around the ion and from scattering theory determine the energy loss directly. Comparison with the results of linear theory is made. 相似文献
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In this study the model suggested by Sugiyama has been developed and applied for the calculation of the stopping powers for nonrelativistic heavy ions in various target materials. Sugiyama's model has been expanded to low and high energy regions in our work. Analytical expressions are obtained in the modified BB stopping power formula for the effective charge and effective mean excitation energies. In the modified LSS formula, a quasi-molecule criterion has been applied to both the projectiles and the target atoms. Electronic excitation contribution, S e0, and quasi-molecule contribution, S ei , to stopping power were found for a wide energy region. It is observed that in intermediate energy region both contributions have maxima. The stopping power due to excitation-ionization in the intermediate and higher energy region is found to be dominant, whereas quasi-molecule contribution is dominant in the lower energy region. The calculated results of stopping power are in good agreement with experimental data for various ions and targets within a few percent in a wide projectile energy range. 相似文献
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P. Sigmund 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(1):45-54
The principle of reciprocity, i.e., the invariance of the
inelastic excitation in ion-atom collisions against interchange of
projectile and target, has been applied to the electronic stopping cross
section of low-velocity ions and tested empirically on
ion-target combinations supported by a more or less adequate amount of
experimental data. Reciprocity is well obeyed (within ~10%) for
many systems studied, and deviations exceeding ~20% are
exceptional. Systematic deviations such as gas-solid or metal-insulator
differences have been looked for but not identified on the present basis.
A direct consequence of reciprocity is the equivalence of Z1 with
Z2 structure for random slowing down. This feature is reasonably well
supported empirically
for ion-target combinations involving carbon, nitrogen, aluminium and
argon.
Reciprocity may be utilized as a criterion to reject questionable
experimental data. In cases where a certain
stopping cross section has not been or cannot be measured, the
stopping cross section for the inverted system may be available and
serve as a first estimate.
It is suggested to build in reciprocity as a fundamental requirement into
empirical interpolation schemes directed at the stopping of low-velocity
ions. Examination of the SRIM and MSTAR codes reveals cases where
reciprocity is obeyed accurately, but deviations of up to a factor of two
are common. In case of heavy ions such as gold, electronic stopping
cross sections predicted by SRIM are asserted to be almost an order of
magnitude too high. 相似文献
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Making use of the inelastic scattering function introduced by Ohtsuki, the position dependent stopping power is derived for energetic ions in a channeling condition. We can interprete the Lindhard theory, Esbensen-Golovchenko theory, and Burenkov-Komarov-Kumakhov theory for the channeling stopping power in terms of our method. Our results agree very well with experiment. 相似文献
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W. Schott H. Daniel F. J. Hartmann W. Neumann 《Zeitschrift für Physik A Hadrons and Nuclei》1993,346(1):81-84
The spectral flux densityn(T) of – emerging from a Au or MgF2 moderator has been measured at low energiesT using time-of-flight. Fromn(T) the stopping powerS(T) of Au was determined for 2 keVT22 keV, and of MgF2 for 2 keVT12 keV. For Au,S(T) is smaller than calculated values obtained from proton atomic data practically in the wholeT range (Barkas effect); at lowT
S(T) approaches the calculated values. For MgF2,S(T) agrees fairly with the calculated values above 5 keV and then drops below these values. We ascribe this dropping to the large energy gap of the MgF2 insulator.We wish to thank H. Angerer, H. Plendl, G. Schmidt, and C.A. Schug for help with the data taking, J. Homolka for computational help, H. Hagn, and H. Weiss for technical assistance and P. Maier-Komor and R. Scherrer for manufacturing the windows and targets. The hospitality of PSI and financial support by the German Bundesministerium für Forschung und Technologie are acknowledged. 相似文献
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The electronic energy loss of hydrogen ions (protons and deuterons) in thin supported films of LiF has been studied in backscattering geometry for specific energies from 700 eV/u to 700 keV/u, using Rutherford backscattering spectroscopy and time-of-flight low-energy ion scattering spectroscopy. For specific energies below 8 keV/u, our data confirm velocity proportionality for the stopping cross section epsilon (like in a metal) down to 3.8 keV/u, as observed previously for protons and antiprotons despite the large band gap (14 eV) of LiF. Below 3.8 keV/u, the present results indicate an apparent velocity threshold at about 0.1 a.u. for the onset of electronic stopping. 相似文献
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Electronic energy loss of light ions transmitted through nanometer films of Al has been studied at very low ion velocities. For hydrogen, the electronic stopping power S is found to be perfectly proportional to velocity, as expected for a free electron gas. For He, the same is anticipated, but S shows a transition between two distinct regimes, in both of which S is velocity proportional-however, with remarkably different slopes. This finding can be explained as a consequence of charge exchange in close encounters between He and Al atoms, which represents an additional energy loss channel. 相似文献
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A comparative study of different energy loss formulations viz. Benton and Henke, Mukherjee and Nayak, Zieglar et al. and Hubert et al. has been done at lower energies (0.5 to 5 MeV/n) with the aim to identify their relative validity in this energy range. Calculated results using these formulations have been compared with experimental results available in literature. 相似文献
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M. Beuve M. Caron B. Gervais H. Rothard A. Clouvas C. Potiriadis 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,15(3):293-300
It is usually well accepted that for swift protons, the induced backward and forward electron emission yield is proportional
to the projectile electronic stopping power. This was observed in particular for thin amorphous carbon foils. However, this
law was established from a non extensive set of experimental data and somewhat confirmed by rough macroscopic theories. We
then developed a standard Monte Carlo simulation to predict the yield dependence on proton energy [0.5–10 MeV] and for a wide
range of foil thickness. After evaluating the reliability of this simulation, we showed and explained why the law of proportionality
cannot generally hold for forward electron emission. In particular, the ratio between forward yield and stopping power generally
depends on foil thickness and proton energy. We performed a new experiment that confirmed our theoretical predictions.
Received 9 March 2001 相似文献
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《Physics letters. A》1987,123(6):307-310
The velocity dependence in the low-velocity electronic stopping power of heavy ions has been studied for Al and Si ions in Ta in the velocity region 0.4v0−4v0 (v0 is the Bohr velocity). The first experimental information is obtained from the range distribution and Doppler-shift-attenuation data. 相似文献
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P. Sigmund L.G. Glazov 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(2):211-215
The electronic energy loss of a dressed ion penetrating through matter is commonly considered as being synonymous with the
sum of the excitation energies of the target and the projectile in atomic collisions undergone during the passage. We show
that this is not justified in projectile-ionizing collisions and discuss some consequences.
Received 23 October 2002 / Received in final form 1st December 2002 Published online 18 February 2003 相似文献
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N. Stevanović D. Nikezić 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(3):397-406
Collision of swift ions with atoms was considered in this paper. The
projectile and target atoms were modeled as assemblies of quantum
oscillators and it was assumed that both, target and projectile could be
excited or ionized, without charge exchange. The model presented here is an
extension of the one given by Sigmund and Haagerup [Phys. Rev. A 34, 892 (1986)]. The number of electrons bound to the projectile, as a function of the projectile velocity,
was used from Cabrera-Trujillo et al. [Phys. Rev. A 55, 2864 (1997)]. Contributions to energy loss from excitation of the projectile and targets were separately considered. It
has been found that projectile excitation contributes up to 20% to the
total energy loss in the lower energy region. Comparisons with other
authors, including SRIM 2003, are also given and good agreement was found. 相似文献