共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
The problem of ionization of ions in ion-ion and ion-neutral relativistic collisions is considered. Formulas for ionization
cross sections are derived in the Born approximation in terms of the momentum transfer without allowance for magnetic interactions.
Using these formulas implemented in the LOSS-R code, the ionization cross sections are calculated for the K shells of neutral atoms colliding with protons and also for 1s and 2p electrons of multiply charged heavy ions (nuclear charge Z = 80−90) colliding with bare nuclei and neutral atoms. The calculation results are compared with experimental data and calculations
of other authors. 相似文献
3.
W.F. Huebner M.F. Argo L.D. Ohlsen 《Journal of Quantitative Spectroscopy & Radiative Transfer》1978,19(1):93-97
Removal of outer electrons from an atom does not significantly change the potential and wave functions over the region where the wave function of the remaining bound electrons is large. This explains why the partial cross sections of an ion are similar to those of its neutral atom but truncated at the ion's threshold. Scaling by the wave-function-effective-Z can significantly improve the accuracy of the ion partial cross sections. 相似文献
4.
S. N. Andreev I. L. Beigman I. Yu. Tolstikhina V. P. Shevelko G. Baur T. Stöhlker 《Bulletin of the Lebedev Physics Institute》2008,35(3):89-95
Ionization processes of heavy ions colliding with atoms and ions at relativistic energies are considered. Formulaes for calculating ionization cross sections in the Born approximation using momentum-transfer representation without regard to magnetic interactions are given as well as those in dipole and impulse approximations. Using the LOSS-R [25] and HERION codes, calculations of relativistic cross sections are performed for H-like multiply changed ions with the nuclear charge Z ≈ 80?90, colliding with neutral atoms and for multiply changed uranium ions colliding with protons and carbon atoms. The results of calculations are compared with available experimental data and calculations performed by other authors. 相似文献
5.
Electron-loss processes arising in collisions of heavy many-electron ions (like U28+) with neutral atoms (H, N, Ar) are considered over a wide energy range including relativistic energies. Various computer
codes (LOSS, LOSS-R, HERION, and RICODE), created for calculation of the electron-loss cross sections, and their capability
are described. Recommended data on the electron-loss cross sections of U28+ ions colliding with H, N, Ar targets and predicted lifetimes of U28+ ion beams in accelerator are given. Calculated electronloss cross sections are compared with available experimental data
and other calculations. 相似文献
6.
The relativistic eikonal approximation and a matching procedure are used to describe excitation and ionization of hydrogen-like atoms from an arbitrary discrete energy state by the impact of a highly charged relativistic bare ion. Bethe-type formulas are derived that are asymptotically valid in the limits of v → c and Z ? 1, where v is the relative collision velocity, c is the speed of light, and Z is the ion charge. 相似文献
7.
A nonperturbative method is developed for the calculation of cross sections of inelastic processes in collisions between structured high-charge heavy ions moving at relativistic velocities and atoms. By structure ions are meant partly stripped ions consisting of an ion nucleus and a number of bound electrons which partly compensate the core charge and form the electron “coat” of the ion. The single ionization cross section of hydrogen atom and single and double ionization cross sections of helium atom are calculated. It is demonstrated that the inclusion of the extent of ion charge may bring about a marked variation of the respective cross sections compared to ionization by point ions of the same charge and energy. 相似文献
8.
Nonperturbative theory is developed for the multiple ionization of fast heavy structure ions colliding with neutral complex atoms. The cross sections for multiple loss of electrons by structure uranium ions U10+ (loss of up to 82 electrons) and U28+ (loss of up to 64 electrons) colliding with argon atoms are calculated. The results are compared with available experimental data. 相似文献
9.
Yu. A. Belkova N. V. Novikov Ya. A. Teplova 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2009,3(2):188-191
The electron-loss cross sections σ i, i + 1 and the electron-capture cross sections σ i, i ? 1 for carbon ions with energies of 35–330 keV/nucleon in hydrogen and neon are determined from experimental data. It is demonstrated that, for particle energies which satisfy the condition σ i, i + 1 = σ i, i ? 1 or σ i, i ? 1 = σ i ? 1, i , the average equilibrium ion charge can be evaluated without solving the system of differential equations for charge exchange. The dependence of the average equilibrium ion charge on the ion energy is investigated for carbon ions. 相似文献
10.
E. Casarejos P. Armbruster L. Audouin J. Benlliure M. Bernas A. Boudard R. Legrain S. Leray B. Mustapha S. Czajkowski T. Enqvist B. Fernandez J. Pereira M. Pravikoff F. Rejmund K. -H. Schmidt C. Stephan J. Taieb L. Tassan-Got C. Villagrasa C. Volant W. Wlazlo 《Physics of Atomic Nuclei》2003,66(8):1413-1420
The isotopic production cross sections of heavy residues in relativistic heavy-ion collisions have been investigated in inverse kinematics. The primary reaction products were fully identified in mass and atomic number prior to beta decay using the fragment separator FRS. The huge collection of data obtained helps in the understanding of the two main reaction mechanisms involved: fragmentation and fission. These data provide basic information for future radioactive ion beam facilities and for technical applications like intense neutron sources by means of spallation targets. 相似文献
11.
W. Arnold H. Berg H. H. Krause G. Clausnitzer 《Zeitschrift für Physik A Hadrons and Nuclei》1980,294(1):7-11
A method for the determination of the cross-section ratioσ ?10/(σ ?11+ (σ ?10) for hydrogen ions in gases is described; the indices refer to the initial and final charge state. The method is based on the fact that a polarized hydrogen ion beam loses a certain amount of its initial polarization during charge exchange from the negative to positive state in the stripper canal of a tandem accelerator. Combined with the beam-attenuation method the individual electron-stripping cross sections (σ ?11, (σ ?10 and (σ ?01 can be obtained. 相似文献
12.
V. I. Matveev 《Journal of Experimental and Theoretical Physics》2002,94(2):217-221
A nonperturbative theory of energy loss in collisions between structural, highly charged heavy ions moving at relativistic velocities and atoms is developed. A simple formula for effective deceleration is derived. By structural ions are meant ions containing partially filled electron shells. It is such ions characterized, as a rule, by a significant charge (for example, partially “stripped” uranium ions) that are used in numerous experiments involving the use of modern heavy-ion accelerators. 相似文献
13.
We explore some of the effects of optical-potential ambiguities on the fusion cross sections for heavy-ion collisions, especially at energies below the top of the Coulomb barrier when the barrier-penetration model is used. Ambiguities of the Igo type in the real potential are found to have little effect except when the potential is very shallow. The cross sections are seen to be very sensitive to the imaginary potential adopted if this allows for some absorption within the barrier; both the magnitude and shape of the excitation function may be changed. 相似文献
14.
M. R. Talukder S. Bose M. A.R. Patoary A. K.F. Haque M. A. Uddin A. K. Basak M. Kando 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(2):281-287
A simple empirical formula is proposed for the rapid
calculation of electron impact total ionization cross sections both for the
open- and closed-shell neutral atoms considered in the range 1≤
Z≤92 and the incident electron energies from threshold to about
104 eV. The results of the present analysis are compared with the
available experimental and theoretical data. The proposed model provides a
fast method for calculating fairly accurate electron impact total ionization
cross sections of atoms. This model may be a prudent choice, for the
practitioners in the field of applied sciences e.g. in plasma modeling, due
to its simple inherent structure. 相似文献
15.
16.
《Physics letters. A》1986,115(7):338-339
The total charge-transfer cross sections in Ca+ + Mg and Ca+ + Sr collisions are investigated experimentally by the crossed-beam technique in the energy range 80–1000 eV. 相似文献
17.
A. Aste G. Baur K. Hencken D. Trautmann G. Scharf 《The European Physical Journal C - Particles and Fields》2002,23(3):545-550
The results concerning the production in peripheral highly relativistic heavy-ion collisions presented in a recent paper by Baltz et al. are rederived
in a very straightforward manner. It is shown that the solution of the Dirac equation directly leads to the multiplicity,
i.e. to the total number of electron–positron pairs produced by the electromagnetic field of the ions, whereas the calculation
of the single pair production probability is much more involved. A critical observation concerns the unsolved problem of seemingly
absent Coulomb corrections (Bethe–Maximon corrections) in pair production cross sections. It is shown that neither the inclusion
of the vacuum–vacuum amplitude nor the correct interpretation of the solution of the Dirac equation concerning the pair multiplicity
is able the explain (from a fundamental point of view) the absence of Coulomb corrections. Therefore the contradiction has
to be accounted to the treatment of the high energy limit.
Received: 30 November 2001 / Published online: 22 February 2002 相似文献
18.
B. Kamke 《Zeitschrift für Physik A Hadrons and Nuclei》1975,273(1):23-28
The disorientation and disalignment cross sections for the depolarization of Rb 52P1/2 and 52P3/2 states due to collisions with the inert gases He, Ne, Ar, Kr, Xe were measured at a temperature of 317 K. The experiments were done in a static magnetic field H0 which served to decouple the nuclear spin. Unpolarized Rb-D2-radiation was made incident on the Rb-vapour parallel to H0 thus generating an alignment in the2P3/2-state. The linear polarization of the fluorescent D2-light emitted at right angles towards the incident light beam was measured as a function of the rare gas pressure (0... 3 Torr). Similarly, for the disorientation measurements the vapour was excited by circularly polarized D2- or D1-radiation parallel to H0 and circularly polarized fluorescent light was observed at small angles towards the backward direction. From the decrease of the polarizations observed at rising pressure the cross sections were determined. The comparison with theoretical results gives satisfactory agreement. 相似文献
19.
20.
A. D. Ulantsev 《Bulletin of the Lebedev Physics Institute》2007,34(8):223-230
The applicability of the geometrical model (GM) proposed in [14, 15] to calculate the ionization probability and cross section of atoms and ions during collisions with ions, including structural ions, was studied at high velocities of partners. The GM represents a version of the classical impulse approximation. It was shown that the GM in all cases under consideration allows estimation of the ionization probability and total corss section of an atom or an ion during collisions with ions with deviations of no more than 50% from the results of the classical Monte Carlo method. GM calculations are rather simple in computation respect and limit the ionization probability by unity at arbitrary impact parameters. 相似文献