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1.
Z1- AND Z2-OSCILLATIONS OF ELECTRONIC STOPPING CROSS SECTIONS OBTAINED BY SHELL-WISE CALCULATION AND HARMONIC-OSCILLATOR MODEL
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A shell-wise calculation method and a quantal harmonic-oscillator model have been used to calculate the electronic stopping cross sections for heavy ions colliding with atoms or penetrating matter. The electronic energy loss is given in an impact parameter formalism. In order to generalize the theoretical models, which pertain to the cese of point charge interacting with matter, to the case for heavy ions, an effective stopping charge hased on the modified BK theory is used by way of simple scaling in the calculations. The comparisons between the calculated results and the experimental data demonstrate a favourable evidence to justify the theoretical models. 相似文献
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The effective charge state is an important particle parameter which is required for the calculation of many effects concerning the interaction between radiation and matter such as an estimate of the radial dose of swift heavy projectiles, stopping power and so on. A new method for the determination of effective charge states of heavy ions is based on the measurement of the number of high-energy delta-electrons which are ejected from a target by the penetrating ion. These electrons are detectable with a CCD-detector and their number can be correlated to the effective charge state of the projectile for known particle velocities. This method is even applicable to operation with single swift heavy ions within statistical bounds. 相似文献
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Vladimir V. Yudin 《Applied Physics A: Materials Science & Processing》1978,15(2):223-228
This paper presents a theoretical analysis and simple expressions for the calculation of ranges and standard deviations of
implanted ions in amorphous targets. Nuclear energy loss models are discussed to introduce an approximation formula for the
nuclear stopping cross section appropriate for Thomas-Fermi, Lenz-Jensen and intermediate type potentials. The Firsov electronic
stopping model has been used to show its successful application. Algebraical expressions for the total range of ions in monoatomic
and biatomic targets as a function of ion energy result from the considerations presented. A quasi-elastic multiscattering
model is suggested, which permits an easy estimate of projected ion ranges. The standard range deviation is obtained by determining
the total average-square energy loss fluctuations. Finally a comparison of calculated and experimental results is made to
show that calculations based on the Firsov electronic stopping model and the nuclear stopping cross section proposed here
provide a better agreement with the experimental results than the wellknown Johnson-Gibbons LSS-calculations. 相似文献
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V. I. Matveev 《Technical Physics》2002,47(5):523-528
A nonperturbative theory of energy loss by relativistic composite heavy highly charged ions colliding with atoms is developed. A simple formula for effective stopping is derived. By composite ions, we mean partially ionized atoms of heavy elements consisting of the ion core and several bound electrons that incompletely neutralize the ion core charge. Such ions, which have, as a rule, a high charge (for example, partly stripped uranium atoms), are used in many experiments performed with modern heavy ion accelerators. 相似文献
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重离子束在等离子体靶中的能量损失 总被引:1,自引:0,他引:1
借助于线性Vlasov方程,我们研究了重离子束在等离子体靶中的有效电荷数和电子阻止本领。在高速情况下,分别得到了它们的解析表示式。以~(40)Ga,~(74)Ge,~(84)Kr,~(110)pd,~(208)pb及~(238)U等重离子束在氢等离子体中的能量损失为例,将我们的理论结果与Hoffmann等人的实验结果进行了比较。 相似文献
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The exchange and correlations between free electrons in metals are shown always to increase electronic stopping power for slow ions. The stopping power is expressed analytically for theoretical evaluations. This expression was used to calculate stopping powers for slow protons in Al and Ag. A better agreement with experimental data is noticed. 相似文献
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P. A. Platonov E. I. Trofimchuk O. K. Chugunov V. I. Karpukhin Yu. P. tumanov S. I. Alexeev 《辐射效应与固体损伤》2013,168(2):105-110
Abstract The electronic stopping of heavy ions with 7 ≤ Z, ≤ 54 in low-index directions of thin gold single crystals is measured in the energy range 200 keV ≤ E ≤ 1100 keV. Large oscillations in electronic stopping power are observed for constant ion velocity. The stopping powers of different low-index directions are compared. 相似文献
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M.W. Mancini A.L. de Oliveira K.M.F. Magalhãaes V.S. Bagnato L.G. Marcassa 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(3):317-322
In an experimental study, the multi-ionisation of metallic clusters (Nan) has been analysed in collisions with light ions in low charge states (H+, He+, He2+, O3+) at collision velocities below 1 a.u. Cluster ions are produced in charge states up to 5+. The average charge of the nano-particles
is found to increase linearly with the variation of projectile velocity and the square of the effective projectile charge,
well in agreement with the electronic stopping power of the bulk material. A fraction of 50% to 30% of the total projectile
energy loss (decreasing with velocity) is transferred into vibrational modes in good agreement with recent theoretical predictions.
Received 8 November 2000 and Received in final form 26 January 2001 相似文献
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Wolfgang Neuwirth Ulrich Hauser Ernst Kühn 《Zeitschrift für Physik A Hadrons and Nuclei》1969,220(3):241-264
A new method of determining the differential energy loss of charged excited nuclei in matter is described. The method is based on the velocity dependence of the Doppler shift of the gamma quanta emitted by moving nuclei. No theoretical assumptions concerning the velocity dependence of atomic or nuclear collisions are necessary. The method and mathematical analysis, described in detail, are applied to the energy loss of Li ions emitting gamma quanta of 477 keV in the kinetic energy range between 100 and 800 keV. It is found that the energy loss of Li ions is linearly proportional to the velocity within 2% for several substances ofZ=1 to 74. The small limits of error, which can be obtained, allow an application of this method to questions as e.g. theZ-dependence of the stopping power on the nuclear charge of the stopping material, chemical binding effects, the time dependence of the adjustment of the equilibrium charge of the projectile after nuclear reactions, or the determination of nuclear angular correlations. 相似文献
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The long-standing problem of the lacking signature of a Barkas effect in the stopping of swift heavy ions under channeling conditions has been analyzed theoretically. The stopping model provides explicit dependences on impact parameter and allows for projectile screening and higher-order Z(1) corrections. The analysis differentiates between principal target shells. A distinct Barkas correction is found in accordance with standard theory. It is less pronounced for channeled than for random stopping because of the dominance of outer target shells. Varying contributions from different target shells to the stopping force may give rise to an inversion of the commonly observed variation with ion energy and charge state of the Barkas correction. 相似文献
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Hadjar O Foldi P Hoekstra R Morgenstern R Schlatholter T 《Physical review letters》2000,84(18):4076-4079
Multiply charged ion-induced fragmentation and ionization of C60 is governed by electronic and nuclear stopping of the projectile as well as charge exchange. We have studied the collision dynamics as a function of the projectile atomic number Z ( 2=Z=18) for constant projectile velocity v at charge states q = 2,3. Strong oscillations of electronic-stopping-related quantities such as ionization and fragmentation are observed. From the properties of the oscillations, we obtain information on the effective electron density of the fullerene. 相似文献
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A nonperturbative theory of the energy losses in collisions of structural multiply charged heavy ions moving with relativistic velocities with atoms is worked out. Within the framework of this theory, by structural ions are meant ions containing partially filled electronic shells. It is such ions, having, as a rule, a considerable charge (for example, completely or partially stripped ions of uranium), that are used in many modern experiments on accelerators of heavy ions. 相似文献
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This topical review focuses on recent advances in the understanding of the formation of surface nanostructures, an intriguing phenomenon in ion-surface interaction due to the impact of individual ions. In many solid targets, swift heavy ions produce narrow cylindrical tracks accompanied by the formation of a surface nanostructure. More recently, a similar nanometric surface effect has been revealed for the impact of individual, very slow but highly charged ions. While swift ions transfer their large kinetic energy to the target via ionization and electronic excitation processes (electronic stopping), slow highly charged ions produce surface structures due to potential energy deposited at the top surface layers. Despite the differences in primary excitation, the similarity between the nanostructures is striking and strongly points to a common mechanism related to the energy transfer from the electronic to the lattice system of the target. A comparison of surface structures induced by swift heavy ions and slow highly charged ions provides a valuable insight to better understand the formation mechanisms. 相似文献
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An estimate of the electronic stopping of a swift cluster ion during different stages of penetration in a given material is presented. We take a simplified approach to the stopping process by neglecting vicinage effects on the stopping cross section as well as spatial distortion due to Coulomb forces among ions. The different stages of penetration and energy loss are based on the hypothesis of formation of a transient plasma (the plasma stopping regime)—due to the release of energetic electrons from the target material—within and around the spatial region defined by the correlated positions of each cluster constituent ion (atom). The density of the transient plasma is treated as a function of the rate of energy deposition and depth up to a point where the rate of energy deposition yields a threshold value where the ejected target electrons immediately recombine so that stopping in a cold target begins (conventional stopping regime) and where the cluster constituent ions start being neutralized according to a charge equilibration scheme as depicted by the effective charge relation of Betz. The model is applied to the stopping of 40.2 Mev C603+ projectiles penetrating an Yttrium–Iron Garnet (YIG) target. Also, in this case, a possible explanation for the experimentally observed cluster-fragmentation events at a certain depth is presented. 相似文献
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P. Sigmund A. Schinner 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,15(2):165-172
Binary theory of electronic stopping, developed recently with the aim of quantifying stopping forces on swift heavy ions,
has been applied to antiproton stopping. Essential ingredients in the theory are inverse-Bloch and shell corrections. The
numerical input consists of the excitation spectrum of the stopping material, characterized by bundled oscillator strengths
extracted from tabulated optical properties. Predicted stopping forces for eight solid materials agree well with experimental
data, in particular for Si where measurements span over two decades of projectile energy. Large discrepancies were found with
stopping data for helium extracted from annihilation time measurements.
Received 22 February 2001 相似文献
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The tracklengths in mica have been measured for iodine and gold ions in the energy range 0 to 1 MeV/amu. These data and those from previous studies have been compared with the Lindhard-Scharff-Schiøtt theory for the stopping of heavy ions in matter. Discrepancies from the theory are discussed. 相似文献