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1.
Young-Dae Jung 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(2):249-254
In strongly coupled plasmas, the orientation phenomena for direct excitations in electron-hydrogenic ion collisions are investigated using the ion-sphere interaction potential. For small
impact parameters, the orientation parameters have minima which correspond to the complete transitions. The target screening effects slightly increase the probability of populating the 2p-1 state.
Received: 16 December 1998 / Received in final form: 23 March 1999 相似文献
2.
K. M. Aggarwal F. P. Keenan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(2):205-213
In a recent paper, Verma et al. [Eur. Phys. J. D 42, 235 (2007)] have reported results for energy levels, radiative rates, collision strengths, and effective collision
strengths for transitions among the lowest 17 levels of the (1s22s22p6)3s23p6, 3s23p53d and 3s3p63d configurations of Ni xi. They adopted the civ3 and R-matrix codes for the generation of wavefunctions and the scattering process, respectively. In this paper, through two
independent calculations performed with the
fully relativistic darc (along with grasp) and fac codes, we demonstrate that their results are unreliable. New data are presented and their accuracy is
assessed. 相似文献
3.
N. Verma A. K.S. Jha M. Mohan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(2):235-241
Electron excitation collision strengths for the transitions from the ground
state to the fine-structure levels of the 3s23p53d and
3s23p63d configurations in Ni XI are calculated using the
Breit-Pauli R-matrix method. Configuration interaction wavefunctions have
been used to represent the target states. The relativistic effects are
incorporated in the Breit-Pauli approximation by including one-body mass
correction, Darwin, and spin-orbit interaction terms in the scattering
equations. Collision strengths are tabulated at selected energies in the
range 10 to 75 Rydberg. Effective collision strengths are determined by
integrating collision strengths by assuming a Maxwellian distribution of
electron energies. The effective collision strengths are listed over a wide
temperature range (2×104-1×107 K) applicable to
astrophysical plasmas. Our results are the only collision strengths and
effective collision strengths available for this ion. We believe that the
data calculated in this work will be useful in solar, astrophysical and
laser applications. 相似文献
4.
J. B. Boffard M. F. Gehrke M. E. Lagus L. W. Anderson C. C. Lin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(2):193-198
This paper describes a method for reducing the influence of cascades on the measurement of electron excitation cross sections
using the optical method and a fast beam atomic target. By using a fast beam of target atoms one can reduce the influence
of cascades on a measurement, and estimate the cascade contribution to the excitation signal.
Received 19 April 1999 and Received in final form 10 August 1999 相似文献
5.
Young-Dae Jung 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(2):291-294
The classical electron-ion Coulomb Bremsstrahlung process is investigated in nonideal plasmas. An effective pseudopotential
model taking into account the plasma screening and collective effects is applied to describe the electron-ion interaction
potential in a classical nonideal plasma. The classical straight-line trajectory method is applied to the motion of the projectile
electron in order to visualize the variation of the differential Bremsstrahlung radiation cross-section (DBRCS) as a function
of the scaled impact parameter, nonideal plasma parameter, projectile energy, photon energy, and Debye length. The results
show that the DBRCS in ideal plasmas described by the Debye-Hückel potential is always greater than that in nonideal plasmas,
i.e., the collective effects reduce the DBRCS for both the soft and hard photon cases. For large impact parameters, the DBRCS
for the soft photon case is found to be always greater than that for the hard photon case.
Received 1st December 1999 相似文献
6.
Young-Dae Jung 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(2):351-354
In nonideal classical plasmas, the electron captures by positrons from hydrogenic ions are investigated. An effective pseudopotential
model taking into account the plasma screening effects and collective effects is applied to describe the interaction potential
in nonideal plasmas. The classical Bohr-Lindhard model has been applied to obtain the electron capture radius and electron
capture probability. The modified hyperbolic trajectory method is applied to the motion of the projectile positron in order
to visualize the electron capture probability as a function of the impact parameter, nonideal plasma parameter, projectile
velocity, and plasma parameters. The results show that the electron capture probability in nonideal plasmas is always greater
than that in ideal plasmas descried by the Debye-Hückel potential, i.e., the collective effect increases the electron capture probability. It is also found that the collective effect is decreased
with increasing the projectile velocity.
Received 21 January 2000 and Received in final form 27 April 2000 相似文献
7.
K.N. Joshipura M. Vinodkumar B.K. Antony N.J. Mason 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(1):81-90
Total ionization cross-sections of electron impact are calculated for the molecular targets CHx, CFx, SiHx, SiFx (x = 1-4) and CCl4 at incident energies 20-3 000 eV. The calculation is based on Complex Scattering Potential approach, as developed by us recently.
This leads to total inelastic cross-sections, from which the total ionization cross-sections are extracted by reasonable physical arguments. Extensive comparisons are made here with the previous theoretical
and experimental data. The present results are satisfactory except for the CFx and SiFx (x = 1-3) radicals, for which the experimental data are lower than most of the theories by more than 50%.
Received 23 May 2002 / Received in final form 24 October 2002 Published online 21 January 2003
RID="a"
ID="a"e-mail: knjoshipura@yahoo.com 相似文献
8.
R. Cheikh J. Hanssen B. Joulakian 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,2(3):203-208
The fivefold differential cross section (5DCS) of the ionisation by electron impact of atomic sodium is determined theoretically
for its fundamental 3s(2
S) state and the excited 3p(2
P) and 3d(2
D) states by a procedure which employs in the transition matrix element of the first order Born approximation, the correlated
double continuum (3C) wave function. This permits us to determine the statistical M-state population and the orientation and alignment tensors in (e,2e) detection. It is also shown that, the use of Gamow correlation term, in the independent particle (2C) model, reproduces,
only in some situations, the shape of the angular distribution of the 5DCS obtained by the (3C) wave function.
Received: 17 November 1997 / Received in final form: 16 March 1998 / Accepted: 21 March 1998 相似文献
9.
L.K. Jha B.N. Roy 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(1):5-10
Electron impact single and double ionization cross-sections for magnesium have been calculated in the binary encounter model
using accurate expression for (cross-section for energy transfer ΔE) as given by Vriens. Hartree-Fock velocity distributions for the target electrons have been used throughout the calculations.
In case of double ionization contributions of inner shell ionization and Auger emission have been included in the present
work. The results obtained in case of single ionization are excellent and at the same time the double ionization cross-sections
show reasonably good agreement with the recent experimental observations. Substantiation of the viewpoint of Peach, and Boivin
and Srivastava that a vacancy in the 2p shell of magnesium leads to double ionization is a remarkable feature of the present investigation.
Received 9 October 2001 / Received in final form 8 January 2002 Published online 28 June 2002 相似文献
10.
B. Nath S. Chattopadhyaya C. Sinha 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(1):31-36
Triple differential cross-sections (TDCS) of a hydrogenic (He+) ion has been studied by positron impact using coplaner geometry for both symmetric and asymmetric kinematics in the intermediate
and medium high incident energy region. TDCS has also been studied of He+ ion by electron impact for symmetric kinematics taking account of the electron exchange effect. The final state wavefunction
is chosen as the correlated 3-body Coulomb wavefunction satisfying the exact asymptotic boundary condition. The long range
Coulomb interaction in the initial channel between the ionic target and the projectile has also been taken into account properly.
For positron impact, the collision is found to be almost recoilless at lower incident energies, in contrast to the strong
recoil peak noted in the case of electron impact ionisation. For electron impact, the exchange effect is found to be significantly
high for equal energy sharing in the final channel.
Received 10 July 1999 and Received in final form 7 December 1999 相似文献
11.
J.-G. Wang T.-Q. Chang C.-Z. Dong T. Kato 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,5(2):167-171
A simplified relativistic configuration interaction method is used to study the dielectronic satellite transition processes.
In this method, the infinite resonant doubly excited states can be calculated, and furthermore, the whole high-n dielectronic satellite transition processes can be treated conveniently by interpolation (rather than extrapolation) in the
frame of Quantum Defect Theory. As an example, we calculate the contributions from high-n dielectronic satellites to the resonance line in helium-like iron, and the results are in good agreement with the experimental measurements.
Received: 16 April 1998 / Revised: 8 September 1998 / Accepted: 14 September
1998 相似文献
12.
Calculation of dielectronic recombination cross sections and rate coefficients for heliumlike carbon
J.-G. Wang T.-Q. Chang Y.-Z. Qu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,2(3):231-235
A simplified relativistic configuration interaction method is used to calculate the dielectronic recombination cross sections
and rate coefficients for heliumlike carbon. In this method, the infinite resonant doubly excited states can be treated conveniently
in the frame of Quantum Defect Theory. Our calculated cross sections are in agreements with the experimental measurements
except for the 1s2lnl'(n=6,7) resonances. The total energy-integrated cross sections and rate coefficients over all dielectronic resonances are in
agreements with the experimental measurements within percent.
Received: 7 July 1997 / Revised: 7 October 1997 / Accepted: 8 December 1997 相似文献
13.
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
14.
A. K.F. Haque M. A. Uddin M. A.R. Patoary A. K. Basak M. R. Talukder B. C. Saha K. R. Karim F. B. Malik 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(2):203-210
The recently modified Kolbenstvedt (MKLV) model [Eur. Phys. J. D 37, 361 (2006)], developed for electron impact ionization (EII) of the K-shell atomic targets, has been extended to generalize
its two parameters in terms of the electronic orbitals nl. The generalized MKLV
(GKLV) with two sets of the species independent parameters for the same nl,
one set for the ionization of inner orbits and another for the outermost orbit, is found
profoundly successful in accounting for the EII cross section data of the K, L and M-shell neutral atoms with atomic numbers
Z = 1-92 for the incident energies up to 1000 MeV
in a consistent manner. 相似文献
15.
O. Keller C. Mang M. Nikola G. Schulz 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(3):309-319
Emission spectra following electron impact on molecules of the homologous series of fluoromethanes CHxF4-x with x=0-4 have been investigated from the near infrared at 700 nm to the ultraviolet VUV-spectral region at 100 nm. Earlier experimental
data for the visible and ultraviolet spectral region were revised and evaluated again on the basis of reliable new data for
the dynamic viscosity of the molecules. The measurement of absolute and relative cross-sections were systematically extended
into the VUV region from 100 nm to 200 nm. The examination of atomic lines as well as molecular band systems in the VUV gives
further insight into the dissociation mechanism and shows that many excited levels even of atomic and molecular species cannot
be populated directly, but only by transitions from higher-lying energy levels. Simple steric effects can be distinguished
from more complex transition phenomena.
Received: 25 February 1998 / Revised: 29 May 1998 and 18 June 1998 / Accepted: 23
June 1998 相似文献
16.
J. P. Santos F. Parente 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(3):339-350
Total ionization cross sections of neutral phosphorus, arsenic,
antimony, and bismuth atoms by electron impact are reported and
compared to the only available experimental results by Freund et al. [Phys. Rev. A 41, 3575 (1990)]. These calculations take into account the possibilities that some
target atoms used in the experiments were in metastable states close
to the ground state, the excitation-autoionization of nsnp4
excited states may be substantial, and the ions produced in
experiments may be in excited, low-lying metastable states. The cross sections for direct ionization calculations are based
on
the BEB model by Kim and Rudd [Phys. Rev. A 50, 3954 (1994)].
Plane-wave Born cross sections scaled by the method developed by Kim
[Phys. Rev. A 64, 3954 032713 (2001)] are used to determine the
contributions from excitation-autoionization. The combination of the BEB model and the scaled Born cross sections
is in agreement with the experimental data by Freund et al. These theoretical data are useful to experimentalists and can
be
used to complete data tables needed for plasma or astrophysical
studies. 相似文献
17.
K. Andersson D. Hanstorp A. Neau S. Rosén H.T. Schmidt R. Thomas M. Larsson J. Semaniak F. Österdahl H. Danared A. Källberg A. Le Padellec 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(3):323-328
Electron Impact Single Detachment (EISD) of F- has been studied using the heavy ion storage ring CRYRING at the Manne Siegbahn Laboratory, Stockholm, Sweden. F- ions stored in the ring were merged with an electron beam in one of the ring sections. Neutral F atoms produced in the EISD
process were detected in the zero-degree direction using a surface barrier detector. The threshold for the detachment process
was found to be around 7.6 eV, thus more than twice the binding energy of F-. The cross-sections increased smoothly up to 55 eV where it reached a maximum of 1.9×10
-16
cm
2
. At higher energies a slow decrease of the cross-section was observed, which follows the energy dependence predicted by the
Bethe-Born approximation. The experiment showed that CRYRING can be used favourably for studies of anions, and several experiments
are forthcoming.
Received 14 June 2000 and Received in final form 11 September 2000 相似文献
18.
J. Sun G. Yu Y. Jiang S. Zhang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(1):83-88
The additivity rule is employed to obtain the total (elastic+inelastic) cross-sections for positron scattering from molecules
including a number of diatomic, polyatomic molecules (H2, N2, HCl, CO2, NH3, SF6, CH4, C2H4 and C3H8) over an incident energy range of 10-1000 eV. The total cross-sections (TCS) of the constituent atoms of molecules are obtained
by employing a complex optical model potential (composed of static, polarization and absorption potential). The present results
are compared with experimental data and other theoretical calculations, good agreement is obtained in intermediate- and high-energy
region.
Received: 11 November 1997 / Revised: 23 March 1998 / Accepted: 16 June 1998 相似文献
19.
J. Martinez C. T. Whelan H. R.J. Walters 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(3):409-414
We consider (e,2e) processes on the 2s and 2p shells
of argon and magnesium. We present triple differential cross
sections in coplanar asymmetric geometry calculated in the Plane
Wave Born, 1st Born and Distorted Wave Born approximations. We show
that the currently available relative experiments can not easily
distinguish between these approximations. We make proposals for
relative experiments where the difference between these approaches
can be more readily observed. 相似文献
20.
M. Bouzidi A. Makhoute M.N. Hounkonnou 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,5(2):159-165
We study the influence of the laser polarization on the electron impact excitation of atomic hydrogen. Our method takes into
account the “dressing” of the target states by including the laser-atom interaction to first order time-dependent perturbation
theory, while the interaction of the laser field with the incident electron is treated to all orders by using the non relativist
Volkov function. The interaction of the fast projectile with the target atom is treated in the first Born approximation. The
calculations are performed via two distinct computations. The first one is based on a direct calculation, the second based on a Sturmian approach. Important
differences appear between the angular distributions depending on the polarization chosen.
Received : 17 february 1998 / Revised : 20 july 1998 / Accepted : 2 september 1998 相似文献