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1.
2.
A. Igarashi L. Gulyás P. D. Fainstein 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(1):73-77
The continuum distorted-wave model with an eikonal initial state for
ionisation is discussed within the framework of the impact-parameter
method. Particular attention is paid to the surface term, which
describes the transition by a distorting potential, and which has been
omitted in all of the previous calculations performed using the model.
However, this term is included in the transition amplitude in a recent
application of the model based upon a quantum-mechanical treatment. The
present study, in which the surface term is evaluated within the
impact-parameter method, shows that this term does not contribute to the
transition amplitude. In describing the electron-ejection mechanism for
a p±–H collision, the cross-sections evaluated using the
impact-parameter model show numerical agreement with those determined in
the quantum-mechanical version. This agreement indicates that the
contribution of the surface term calculated in the wave treatment
is negligible over the region in which the impact-parameter model is
valid. 相似文献
3.
K. Orlovsky V. Grushevsky A. Ekers 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(1):133-146
We present results of theoretical studies of the non-resonant excitation transfer in Rb(7S) + Rb(5S) and Rb(5D) + Rb(5S) collisions
at thermal collision energies. Rb2 adiabatic molecular terms correlating with the 5S+7S, 5S+5D and 5P+5P states of separated atoms were calculated for internuclear
distances R > 20 a.u. using asymptotic approximation. Mechanisms of collisional population and quenching of the 5D state were treated
on the basis of the computed molecular terms, and the respective cross-sections were calculated. Theoretical cross-sections
are in good agreement with the experimental values at thermal collision energies ( K).
Received 13 November 1998 and Received in final form 22 November 1999 相似文献
4.
E. Biémont P.-D. Dumont H.P. Garnir P. Palmeri P. Quinet 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(2):199-204
Theoretical transition probabilities have been obtained for 54 n = 3 transitions depopulating the 3s3p
1Po, 3p2
3P, 1D, 1S, 3s3d
1D, 3D and 3p3d
3Po, 3Do, 3Fo, 1Fo, 1Do, 1Po levels, including 14 transitions not yet observed. Some of these predictions have been compared with experimental lifetimes
obtained by beam-foil spectroscopy for four n = 3 levels of K7+. An excellent agreement is observed between theory and experiment for all the levels.
Received 23 January 2002 / Received in final form 23 April 2002 Published online 19 July 2002 相似文献
5.
Summary The collision-assisted electric-quadrupole transition 4s
21
S
0→4s3d
1
D
2 of calcium at 4575 ? has been observed using the laser-enhanced ionization technique for the first time. A blue satellite
band due to the interaction of calcium 4s3d
1
D
2 state with argon1
S
0 has also been detected at 4527 ? which is shifted by 48 ? from the isolated atomic calcium line. The line broadening cross-section
for the blue satellite has been calculated by measuring its collisional broadening at various argon pressures. Important processes
involved in the generation of this blue satellite band are qualitatively discussed.
The authors of this paper have agreed to not receive the proofs for correction. 相似文献
6.
Chen Guo-xin P.P. Ong 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,6(2):153-156
Relativistic distorted-wave method was used to calculate the electron impact excitation collision strengths for transitions
2
s2
1
S0-2
s
2
p
3
P1 of Be-like isoelectronic ions. The target states were described, respectively, by 10-level, 46-level and 133-level MCDF configuration-expansion.
The relativistic continuum orbitals were calculated in the potential field of frozen target-ion charge distribution with semi-classical
exchange potential. The influence of the target states on this collision process along the isoelectronic sequence was investigated
in the above three MCDF configuration-expansion modes. It was found that the configurations in the n
=3 and the n
=4 complexes have great influence on both the high and the low Z ions but the influence is relatively small for intermediate Z ions. The latter phenomenon was attributed to competition between opposing correlation and relativistic effects on the collision
strengths.
Received: 25 February 1998 / Received in final form: 18 June 1998 相似文献
7.
M.J. Singh S.K. Goel R. Shanker D.O. Kataria N. Madhavan P. Sugathan J.J. Das D.K. Avasthi A.K. Sinha 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(1):7-13
Measurements were carried out to deduce the transverse kinetic energies of highly charged argon recoil ions produced in single
collisions of 120 MeV ions with argon atoms in which the post collision charge states of the projectiles were not determined. A time of flight
spectrometer was designed and fabricated to detect the charge states of recoils. Experimental procedures for optimizing the
spectrometer for extraction, transmission and detection of recoils are described. A simple approach for determining the transverse
kinetic energy of the recoil ions from FWHM of the peaks is reported. This method is shown to be independent of the choice
of collision partners and requires only the knowledge of the physical values of “optimized parameters” of time-of-flight spectrometer
used in the experiment. The transverse kinetic energy of the recoil ions determined from the present approach is found to
vary from 0.03 eV for to 4.02 eV for Ar10+. These values are compared with the results reported by earlier workers and are shown to follow a q2-behaviour up to a charge state q
=8+ of the recoil ions.
Received: 5 February 1998 / Revised: 8 June 1998 / Accepted: 11 June 1998 相似文献
8.
9.
A. Salin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(2):189-192
We show that a classical Impact Parameter Method may be derived when taking fully into account the smallness of the ratio
between the electron and nuclear masses. It allows to calculate, exactly as in the quantum version, projectile scattering
and therefore recoil momenta required for the interpretation of recent measurements. We prove an additivity theorem which allows, in particular, to reduce the n-non-interacting electron problem to a set of n one-electron problems. Consequences for the interpretation of target recoil measurements are discussed.
Received 25 June 1999 相似文献
10.
A. Ekers M. Głódź J. Szonert B. Bieniak K. Fronc T. Radelitski 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(1):49-58
The results of an experimental study of population dynamics following excitation of [0pt] and [0pt] states of rubidium are reported. Excitation transfer and quenching cross-sections in collisions with ground state rubidium
atoms, and natural lifetimes have been measured. The experiment was performed in a vapour cell, using pulsed two-photon excitation
and photon counting detection. The analysis of time dependent signals was based on a rate equation model in which transitions
induced by thermal radiation have been accounted for. The measurements yielded following results: (1) [0pt] state J-mixing cross-section: [0pt] ; (2) cross-sections for [0pt] excitation transfer process: [0pt] ; (3) quenching cross-sections: [0pt] , [0pt] , [0pt] ; [0pt](4) radiative lifetimes: [0pt] ns, [0pt] ns, [0pt] ns.
Received 1st December 1998 and Received in final form 17 May 1999 相似文献
11.
Dynamics of ionization mechanisms in relativistic collisions involving heavy and highly-charged ions
D.C. Ionescu A. Belkacem 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(3):301-307
The dynamics of mechanisms associated with the ionization of inner-shell electrons in relativistic collisions involving heavy
and highly-charged ions is investigated within a nonperturbative approach formulated explicitly in the time domain. The theoretical
treatment is based on the exact numerical solution of the time dependent Dirac equation for two Coulomb centers on a lattice
in momentum space. We present results for ionization in encounters between 100 MeV/u Au79+ projectile ions impinging on a hydrogen-like uranium target. By directly visualizing the collision dynamics we identify a
new ionization mechanism in which electrons are emitted from the internuclear region preferentially in the transverse direction
with respect to the projectile trajectory. A striking characteristic of this ionization mechanism is that the velocity of
the electron is higher than the projectile velocity.
Received 26 June 2001 and Received in final form 27 November 2001 相似文献
12.
Dr. Minakshi L. K. Jha S. N. Chatterjee B. N. Roy 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,51(3):331-339
H+ and He2+ impact single and double ionization cross
sections of ground state lead atoms have been calculated in the binary
encounter approximation. Calculations of direct double ionization cross
sections have been performed in the modified double binary encounter model.
The accurate expressions of σΔE (cross-section for energy
transfer ΔE) and Hartree-Fock velocity distributions for the target
electrons have been used throughout the calculations. Contributions to
double ionization from Auger effect following ionization of inner shells
have been considered in the present work. Our H+ impact single and
double ionization cross sections are in good agreement with the experimental
observations. In calculations of He2+ impact cross sections, the
present theoretical approach shows limited success in the experimentally
investigated region (50–350 keV amu-1). 相似文献
13.
E. Träbert U. Staude P. Bosselmann K.H. Schartner P.H. Mokler X. Tordoir 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,2(2):117-123
N
=3, intercombination transitions in Al-like ions of Au have been studied by time-resolved EUV spectroscopy of foil-excited ion
beams. Wavelengths and lifetimes are compared to the available relativistic calculations. The theoretical data are found to
be useful for guidance, but of clearly insufficient precision, in particular for the transition probabilities.
Received: 23 February 1998 / Accepted: 5 March 1998 相似文献
14.
L. Feng Y.-k. Ho 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(1):25-30
In this paper, ion-atom and ion-ion collisions in the presence of intense laser fields are qualitatively studied by Classical
Trajectory Monte Carlo (CTMC) simulations. It is found that in contrast to the field-free collisions, the colliding ion and
the target nucleus could absorb energy from the applied laser fields when the electrons escape from the collision system.
This result is explained in terms of Coulomb explosion induced by the enhanced ionization at the so-called critical internuclear
distance. Also, the corresponding energy gain cross-sections are evaluated.
Received: 7 October 1998 / Received in final form: 28 January 1999 相似文献
15.
16.
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
17.
É. Biémont M. Clar V. Fivet H.-P. Garnir P. Palmeri P. Quinet D. Rostohar 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(1):23-33
Radiative lifetimes have been calculated for 15 levels of Xe VII belonging to the configurations 5s5p, 5p2, 5s5d, 5s6s, 5p5d, 4f5p, 5p5d and 5s5f and for 4 levels of the 5p and 5d configurations of Xe VIII. A relativistic Hartree-Fock
approach including core-polarization effects, on the one hand, and a purely relativistic multiconfiguration Dirac-Fock method,
on the other hand, have been used for the calculations. The accuracy of the present set of results has been assessed through
comparisons with radiative lifetime measurements obtained by beam-foil spectroscopy. A good agreement between theory and experiment
is observed for most of the levels. A new set of transition probabilities is proposed for 169 transitions of Xe VII and 45
transitions of Xe VIII. 相似文献
18.
E. De Filippo G. Lanzanò H. Rothard C. Volant A. Anzalone N. Arena M. Geraci F. Giustolisi A. Pagano 《The European Physical Journal A - Hadrons and Nuclei》2007,32(3):349-356
A rather complete experimental study of forward and backward electron velocity spectra from thin foils bombarded with ions
at constant velocity of 30 atomic units (23MeV u^-1) was performed. Three different beams ( 12C3+ , 58Ni14+ and 197Au36+ and six different targets ( 12C , 27Al , natNi , natAg , 197Au and 209Bi of approximately 90μg cm^-2 thickness were used. This procedure allowed to study the evolution of electron emission (velocity
and angular distributions) for the [projectile; target] matrix [ C , Ni , Au ; C , Al , Ni , Ag , Au , Bi ] in a wide angular
range. The projectile and target dependence of absolute cross-sections for binary encounter-, Auger- and backward-emitted
electrons are analyzed. 相似文献
19.
K.R. Rao Y.R. Krishna P. Venkateswarlu K.B. Rao V.S. Rao G.J.N. Raju S.B. Reddy 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,15(3):283-286
A method is suggested to effect the self absorption correction in a different way to estimate the K X-ray intensity ratios
particularly when heavy ions are used as projectiles. Employing this method, the Kβ/Kα intensity ratios are measured in some 3d shell elements by using Carbon and Nitrogen ions as exciting agents. The Kβ/Kα intensity ratios thus obtained in the present work are compared with the intensity ratios due to some previous authors and
also with Scofield theoretical values.
Received 14 August 2000 and Received in final form 3 January 2001 相似文献
20.
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