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1.
The cross sections for single and double electron capture to the states Ne9+
n) with n=3–6 and Ne8+(3l,n′l′), Ne8+(4l,n′l′) with n′⩾4 and also the cross sections for single electron capture to the states Ne5+(3) in collisions of Ne10+ and Ne6+ with He atoms are calculated for collision energies in the interval from 10 to 150 keV. The calculation is carried out in
the multichannel Landau-Zener, Nikintin, and Landau-Zener-Chaplik models with allowance for the radial coupling of the channels
at crossing points of the energies of the quasidiabatic twoelectron states of the quasimolecule. The energies of the two-electron
states are calculated in the effective potential method to first order in perturbation theory in the residual electron-electron
interaction. The energies of the adiabatic states in the neighborhoods of the crossings of quasidiabatic terms are determined
by the configuration interaction method. It is found that in Ne10+-He collisions the electron is captured mainly to the n=5 state of the Ne9+ ion. The cross section for double electron capture to the 3lnl′ state (n⩾4) of the Ne8+ ion is an order of magnitude smaller than the cross section for single electron capture. The contribution to the total cross
section for double electron charge transfer from the 4l4l′ 4l5l′, and 4l6l′ states is approximately 25%. The dependence of the cross sections for double electron charge transfer on the values of l and l′ is investigated.
Zh. Tekh. Fiz. 69, 15–28 (January 1999) 相似文献
2.
3.
Coulomb deexcitation differential cross sections of excited muonic hydrogen in collisions with the hydrogen atom are studied
for the first time. In the fully quantum-mechanical close-coupling approach, both the differential cross sections for the
nl → n′l′ transitions and l-averaged differential cross sections have been calculated for the initial exotic atom states with n = 2–6 at kinetic energies of E
cm = 0.01–15 eV and for scattering angles of ϑcm = 0°–180°. The vacuum polarization shifts of the ns states are taken into account. The differential cross sections of the elastic and Stark scattering obtained in the same approach
are also presented. The main features of the calculated differential cross sections are discussed, and a strong anisotropy
of Coulomb deexcitation cross sections is predicted.
The text was submitted by the authors in English. 相似文献
4.
The formation of an antiprotonic hydrogen atom $\{ p\bar p\} $ (protonium) in the ground state and in excited states (nlm) in collisions of 1-to 250-keV antiprotons with hydrogen atoms is considered theoretically. Partial cross sections (both differential and integrated ones) for this reaction are calculated for various values of n, l, and m up to n~100; cross sections summed over l and m are also obtained. Statistical (polarization) tensors of the orbital angular momentum of protonium atoms are evaluated. Corrections due to strong proton-antiproton interaction in the protonium ground (1s) state are analyzed. 相似文献
5.
S. Kumari S. N. Chatterjee L. K. Jha B. N. Roy 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,61(2):355-363
H+ impact single and He2+ impact single and double electron
capture cross sections of magnesium atoms have been calculated in the
modified binary encounter approximation (BEA). The accurate expressions of
ion impact sDE\sigma _{\Delta {E}} (cross section for energy transfer
DE\Delta E) and Hartree-Fock momentum distributions of the target
electrons have been used throughout the calculations. On the basis of the
present work it is concluded that inner shell captures by H+ and
He2+ ions incident on magnesium atoms contribute partly to single
electron capture and partly to transfer ionization cross sections. The
calculated He2+ impact double electron capture cross sections of
magnesium are in reasonably good agreement with the experimental
observations. This indicates the success of the present theoretical approach
in study of charge transfer cross sections of atoms as indirect mechanisms do
not interfere with double electron capture processes in this case. 相似文献
6.
M. A. Abdel-Raouf S. Y. El-Bakry A. H. Moussa M. El-Shabshiri 《Czechoslovak Journal of Physics》1989,39(10):1066-1088
The inelastic scattering of positrons by lithium atoms has been investigated in details using a combination of the frozen-core and coupled-static approximations. The ground state of the target has been described by Walters' wave functions. The partial cross sections corresponding to 8 values of the total angular momentuml (0l7) are determined for 21 values of the incident energy lying between 0·1 and 1000 eV. Our results illustrate the stability of the iterative numerical technique employed. They demonstrate the role played by each partial wave in the total cross sections and emphasize the argument that the effect of positronium formation on the total collisional cross sections diminishes when the incident energy is larger than 30 eV. 相似文献
7.
A. A. Narits E. S. Mironchuk V. S. Lebedev 《Journal of Experimental and Theoretical Physics》2013,117(4):607-622
Electron-transfer processes are studied in thermal collisions of Rydberg atoms with alkaline-earth Ca(4s 2), Sr(5s 2), and Ba(6s 2) atoms capable of forming negative ions with a weakly bound outermost p-electron. We consider the ion-pair formation and resonant quenching of highly excited atomic states caused by transitions between Rydberg covalent and ionic terms of a quasi-molecule produced in collisions of particles. The contributions of these reaction channels to the total depopulation cross section of Rydberg states of Rb(nl) and Ne(nl) atoms as functions of the principal quantum number n are compared for selectively excited nl-levels with l ? n and for states with large orbital quantum numbers l = n ? 1, n ? 2. It is shown that the contribution from resonant quenching dominates at small values of n, and the ion-pair formation process begins to dominate with increasing n. The values and positions of the maxima of cross sections for both processes strongly depend on the electron affinity of an alkaline-earth atom and on the orbital angular momentum l of a highly excited atom. It is shown that in the case of Rydberg atoms in states with large l ~ n ? 1, the rate constants of ion-pair formation and collisional quenching are considerably lower than those for nl-levels with l ? n. 相似文献
8.
The total cross sections for positron impact on hydrocarbons have been calculated using the additivity rule in which the total
cross section for a molecule is the sum of the total cross section for the constituent atoms. The energy range considered
is from a few eV to several thousand eV. The total cross sections for positron impact on an atom are calculated by employing
a complex spherical potential which comprises of a static, polarization and an absorption potential. We have good agreement
with the experimental results for hydrocarbons for positron energy ⩾100 eV. Our results also agree with the available calculations
for CH4 and C2H2 which employed full molecular wavefunctions beyond 100 eV. Our absorption cross sections also agree with molecular wave-function
calculations for C2H2 and CH4 beyond 100 eV. We have shown the Bethe plots fore
+−C ande
+−H scattering systems and Bethe parameters have been extracted. We have fitted the cross section for positron impact on hydrocarbons
in the formσ
t(C
n
H
m
)=naE
−
b+mcE
−
d in the energy range 300–5000 eV wherea=195.0543,b=0.7986,c=371.1757 andd=1.1379 withE in eV andσ
t in 10−16 cm2. 相似文献
9.
利用修改后的MBELL模型,研究了L壳层的相对论效应和离子效应对快电子碰撞电离Lα X射线产生截面的影响.通过在BELL模型中引入相对论效应和离子效应,基于相对论性的L壳层的电子碰撞电离截面的理论,计算了Ga,As,Pt,W和Au的L壳层电子碰撞电离截面,并将其转化成Lα X射线产生截面,计算结果表明考虑到相对论效应和离子效应后,修改后的MBELL的Lα X射线产生截面结果明显优于BELL的计算结果,并和最近的文献实验数值
关键词:
快电子
Lα射线')" href="#">Lα射线
电离截面
相对论效应 相似文献
10.
The Coulomb deexcitation of muonic hydrogen in collisions with the hydrogen atom has been studied in the framework of the fully quantum-mechanical close-coupling method for the first time. The calculations of the l-averaged cross sections of the Coulomb deexcitation are performed for (μp)n and (μd)n atoms in the initial states with the principal quantum number n = 3–9 and at relative energies E = 0.1–100 eV. The obtained results for the n and E dependences of the Coulomb deexcitation cross sections drastically differ from the semiclassical results. An important contribution of the transitions with Δn > 1 to the total Coulomb deexcitation cross sections (up to ~37%) is predicted. 相似文献
11.
S. Tomita J.S. Forster P. Hvelplund A.S. Jensen S.B. Nielsen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):119-122
We have measured attenuation cross sections and fragmentation cross sections for protonated water clusters H(H2O)n
+ (n = 1 to 100) colliding with noble gas atoms (He and Xe) at a laboratory energy of 50 keV. In collisions with He, a transparency
effect in the attenuation cross section was observed. For the case of fragmentation in collisions with Xe, a strong enhancement
of small clusters was observed which we attribute to multifragmentation.
Received 30 November 2000 相似文献
12.
T. Kirchner H. Tawara I. Yu. Tolstikhina A. D. Ulantsev V. P. Shevelko Th. Stoehlker 《Technical Physics》2006,51(9):1127-1136
Multielectron ionization of neutral atoms by fast positive ions is considered in terms of the independent particle model. A relatively simple technique for calculating the multielectron ionization probabilities and cross sections through the impact parameter is suggested in which one-electron ionization probabilities are represented as normalized exponentials p nl(b) = p nl(b) = p nl(0)exp(?αnl b), where b is the impact parameter and n and l are quantum numbers of the target atomic shell. Exponent αnl is determined from the Born one-electron ionization cross section for target atoms, and preexponential p nl(0) (the ionization probability at a zero impact parameter) is found from a geometrical model. This technique provides the normalization condition p nl(b) ≤ 1 irrespective of the velocity and charge of striking ions and makes it possible to calculate the one-, two-, and three-electron ionization cross sections, which, when added up, make a major contribution to the total cross section, up to a factor of 2. The results of our computations are compared with experimental data and analytical results of other authors. 相似文献
13.
J. Hüfner Y.B. He B.Z. Kopeliovich 《The European Physical Journal A - Hadrons and Nuclei》2000,7(2):239-244
Prompt gluons are an additional source for charmonium suppression in nuclear collisions, in particular for nucleus-nucleus
collisions. These gluons are radiated as bremsstrahlung in N-N collisions and interact inelastically with the charmonium states
while the nuclei still overlap. The spectra and mean number <n
g> of the prompt gluons are calculated perturbatively and the inelastic cross section σabs
Ψg is estimated. The integrated cross sections σ(A B →J/ψX) for p-A and A-B collisions and the dependence on transverse energy for S-U and Pb-Pb can be described quantitatively with
some adjustment of one parameter <n
g>σabs
Ψg.
Received: 20 August 1999 相似文献
14.
When fast
Xq+ X^{q^ + }
ions collide with atomic or molecular targets, the total charge exchange cross section decreases with increasing target density.
This is because the excitation levels of resulting
X(q - 1)+ X^{(q - 1)^ + }
ions are suppressed because of ionization by target atoms. The effect of target density on the total charge exchange cross
section may amount to one order of magnitude or more depending on the charge and energy of an incident ion, as well as on
the density and inner shell configuration of target atoms. Numerical calculations are performed for partial (in the principal
quantum number n) cross sections σ(n) and total cross sections σtot=Σnσ(n) of charge exchange in the case of collisions of fast multiply charged ions having an energy E in the range 100 keV/u-10 MeV/u with gas or solid targets. 相似文献
15.
We have investigated the heaviest one-neutron halo candidate, the 19C nucleus. Few-body model calculations of cross-section angular distributions for the 19C(p,d)18C reaction together with test calculations carried out for the 17C(p,d)16C reaction at a low incident energy are presented for different possible halo-neutron configurations. We show that there is
a clear distinction in particular between l
n
= 0 and l
n
= 2 halo transfers. The sensitivity of the cross sections to the assumed 19C single-neutron separation energy is discussed.
Received October 13, 1999; revised November 25, 1999; accepted for publication April 29, 2000 相似文献
16.
M. Vinodkumar K. Korot P. C. Vinodkumar 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,59(3):379-387
In this article, we report calculations of total
ionization cross sections, Q
ion
, for simple atoms (C, N, O, F) and
molecules (NO and NH3)_{3}) of atmospheric interest on electron impact at
energies from threshold to 2000 eV. We have employed the complex scattering
potential – ionization contribution (CSP-ic) method for the present study.
Attempt has been made to improve the method by computing the parameter that
involves the ratio of sum of the total excitation cross sections
(Σ
Q
exc
) and total inelastic cross section (Q
inel
) at the peak of the
inelastic cross section. The present study not only provided a better
estimation of the parameter involved in the CSP-ic method but also provided
better agreement with the available experimental and theoretical data on the
ionization cross sections of the simple atomic and molecular targets studied
here. 相似文献
17.
N. V. Novikov Ya. A. Teplova 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2008,2(3):360-363
The single electron loss cross sections for fast B, N, and Ne ions colliding with He atoms are calculated. In the calculation of the ionization amplitude, the He nucleus screening is taken into account by both the sum rule and the summation over a finite number of excited 1snl (n < 5, l < 2) states and states of the continuous spectrum. The calculated results agree satisfactorily with experimental data. 相似文献
18.
M. Ya. Amusia A. S. Baltenkov L. V. Chernysheva 《Journal of Experimental and Theoretical Physics》2008,107(2):180-189
We suggest a prominent modification of the outer shell photoionization cross section in noble gas (NG) endohedral atoms NG@C
n
under the action of the electron shell of fullerene C
n
. This shell leads to two important effects: a strong enhancement of the cross section due to fullerene shell polarization
under the action of the incoming electromagnetic wave and to prominent oscillation of this cross section due to the reflection
of a photoelectron from the NG by the fullerene shell. Both factors lead to powerful maxima in the outer shell ionization
cross sections of NG@C
n
, which we call giant endohedral resonances. The oscillator strength reaches a very large value in the atomic scale, 25. We
consider atoms of all noble gases except He. The polarization of the fullerene shell is expressed in terms of the total photoabsorption
cross section of the fullerene. The photoelectron reflection is taken into account in the framework of the so-called bubble
potential, which is a spherical δ-type potential. It is assumed in the derivations that the NG is centrally located in the
fullerene. It is also assumed, in accordance with the existing experimental data, that the fullerene radius R
C is much larger than the atomic radius r
A and the thickness ΔC of the fullerene shell. As was demonstrated recently, these assumptions allow us to represent the NG@C
n
photoionization cross section as a product of the NG cross section and two well-defined calculated factors.
The text was submitted by the authors in English. 相似文献
19.
V. A. Kartoshkin 《Optics and Spectroscopy》2010,109(5):674-679
Complex cross sections of the spin exchange are calculated for the first time for interacting Na and K atoms based on the
data on the singlet (X
1Σ+) and triplet (a
3Σ+) potentials that describe the interaction of these alkali-metal atoms in the ground state. The obtained cross sections allow
one to theoretically consider the polarization transfer processes and calculate the relaxation times and the magnetic resonance
frequency shifts caused by Na-K spin-exchange collisions. 相似文献
20.
N. L. Manakov A. V. Merem’yanin 《Journal of Experimental and Theoretical Physics》1997,84(6):1080-1089
Using the electric dipole approximation, we present, in invariant form, the cross section of an arbitrary three-photon transition
between the discrete states of an atom with total angular momenta J
i and J
f. The cross section contains scalar and mixed products of the photon polarization vectors, and invariant atomic parameters
dependent only on the photon frequencies. We determine the number of independent atomic parameters at fixed values of J
i and J
f and obtain their explicit expressions in terms of the reduced composite dipole matrix elements. The polarization dependence
of the cross sections is expressed in terms of the degrees l and ξ of linear and circular photon polarizations. We analyze the phenomenon of dissipation-induced circular dichroism in three-photon
processes, i.e., the difference Δ of the cross sections for opposite signs of the degree of circular polarization of all the
photons. We study in detail the case of two identical photons and the phenomenon of elliptical dichroism, when Δ∼lξ holds and dichroism occurs only when the photons are elliptically polarized, with 0<|ξ|<1. Finally, we discuss the dissipation-induced effects of atom polarization in three-photon processes involving linearly
polarized or unpolarized photons.
Zh. éksp. Teor. Fiz. 111, 1984–2000 (June 1997) 相似文献