共查询到20条相似文献,搜索用时 31 毫秒
1.
N.F. Allard J. Kielkopf I. Drira P. Schmelcher 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(2):263-268
We present a theoretical profile of the Lyman line of atomic hydrogen perturbed by collisions with neutral hydrogen atoms and protons. We use a general unified theory
in which the electric dipole moment varies during a collision. A collision-induced satellite appears on Lyman , correlated to the asymptotically forbidden transition of H2. As a consequence, the appearance of the line wing between Lyman and Lyman is shown to be sensitive to the relative abundance of hydrogen ions and neutral atoms, and thereby to provide a temperature
diagnostic for stellar atmospheres and laboratory plasmas.
Received 15 January 2000 and Received in final form 17 May 2000 相似文献
2.
F. Arias de Saavedra E. Buendıa F.J. Gálvez A. Sarsa 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(2):201-206
A generalized Hylleraas-type basis set with three nonlinear parameters is proposed to study three-body systems interacting
via coulomb forces within the framework of non-relativistic quantum mechanics. This basis set improves the rate of convergence
with respect to previous ones, specially for non-symmetric systems and excited states of two electron atoms. Accurate binding
energies and other properties for S-states of helium-like ions, muonic molecules and the positronium negative ion are reported.
Received 21 July 2000 and Received in final form 4 October 2000 相似文献
3.
V. Milosavljević S. Djeniže 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(3):385-390
On the basis of the precisely recorded 706.52 nm He I line shape we have obtained the basic plasma parameters i.e. electron temperature (T) and electron density (N) using our new line deconvolution procedure in the case of five various plasmas created in a linear, low-pressure, pulsed
arc discharge. Plasma parameters have been also measured using independent experimental diagnostical techniques. Excellent
agreement was found among the two sets of the obtained parameters. This enables our deconvolution procedure to recommendation
for plasma diagnostical purposes, especially in astrophysics where direct measurements of the plasma parameters (T and N) are not possible. Besides, on the basis of the observed asymmetry of the Stark broadened line profile we have obtained its
ion broadening parameter (A) caused by influence of the ion microfield to the line broadening mechanism and also the influence of the ion dynamic effect
(D) to the line shape. Our A and D parameters represent the first data obtained experimentally using the line profile deconvolution procedure. We have found
stronger influence of the ion contribution to the 706.52 nm He I line profile than the existing theoretical approximations
estimate. This can be important for plasma modeling or for diagnostics.
Received 30 October 2002 Published online 15 April 2003
RID="a"
ID="a"e-mail: vladimir@ff.bg.ac.yu 相似文献
4.
J.M. Weber I.I. Fabrikant E. Leber M.-W. Ruf H. Hotop 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(2):247-256
Using laser photoelectron attachment to methyl iodide clusters in a differentially-pumped seeded supersonic helium beam and
mass spectrometric ion detection, we have measured the rate coefficients for formation of (q = 0-2) ions over the electron energy range 0-100 meV with an effective energy width of about 2.5 meV. Whereas a prominent
vibrational Feshbach resonance just below the onset for the C-I stretch vibration ( ) is observed for dissociative attachment to monomers (yielding I- ions), only weak and broad structure, shifted to lower energies, is detected for formation of ions and essentially no structure is left in the attachment spectrum for . These observations are interpreted by model R-matrix calculations which successfully describe the DA cross-section for the monomer and qualitatively recover the trend
observed for cluster ion formation. For the clusters, the effects of increased electron-target long-range interaction and
of solvation as well as coupling to soft vibrational modes lead to strong broadening and shifting of the vibrational Feshbach
resonance and, ultimately, to its disappearance.
Received 29 November 1999 and Received in final form 14 January 2000 相似文献
5.
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
6.
J. A. Pomarico D. I. Iriarte H. O. Di Rocco 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(1):65-72
In this paper we analyze the variations in line intensities ratios due to a non-equilibrium situation and to optical depth
effects. A four level model is proposed and the two particular situations for the possible transitions are considered. Electron
density and temperature as well as the source thickness are used as independent parameters to find out in which way and extent
they modify the ratios of levels populations compared with the ideal case of an equilibrium state and optically thin source.
Accordingly with the ion of interest, electron temperatures ranging from I/20 to I/7 eV (I being the ionization energy), whereas electron densities in the interval from 1014 to 1020 cm-3 will be considered. These ranges are of special interest for diverse applications such as LIBS and measurement of transition
probabilities. Some results are presented for real ions and a new expression for the escape factor is also proposed for general
plasma conditions.
Received 12 June 2001 and Received in final form 24 October 2001 相似文献
7.
D.V. Fisher Y. Maron 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(3):349-359
Accurate treatment of the plasma density effects requires a detailed knowledge of the spatial distribution of individual ions
around a test ion. In the present work, rigorous expressions are derived for the main 2- and 3-particle spatial distribution
functions involving the nearest neighbor (NN) and the next-nearest neighbor (NNN) ions. These expressions, valid for both
ideal and nonideal plasmas, present the distributions as functionals of the potentials U
NN and U
NNN at the nearest and next-nearest ion locations. All of the distribution functions except one are derived and discussed in
the present work for the first time ever. For utilization of our results in practical calculations, we suggest semi-empirical
expressions for U
NN and U
NNN in the ion-ion coupling parameter range 0 ?Γ < 1. In order to test the accuracy of our expressions for U
NN and U
NNN we conduct Molecular Dynamics (MD) simulations. The simulations utilize the pure Coulomb particle-particle interaction potentials,
regularized at close range to avoid classical Coulomb collapse, and are free from the assumptions made to find U
NN and U
NNN. Thus, the results of the MD simulations provide an independent test of our theoretical results. Excellent agreement has
been found between the results of the theory and of the MD simulations. Finally, we outline the implications of the present
findings on the problem of tunneling and charge exchange in dense plasmas.
Received 27 October 2000 and Received in final form 30 January 2001 相似文献
8.
S. Hémon A. Berthelot Ch. Dufour F. Gourbilleau E. Dooryhée S. Bégin-Colin E. Paumier 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(4):517-523
The irradiation effects induced by swift heavy ions are now widely described in `bulk' materials. It is shown here that the
behaviour of matter under irradiation depends on its crystalline state in the sense that a given material is all the more
sensitive to swift heavy ion irradiations as the mean crystallite size L is small. The present paper relates the experimental results obtained in yttrium oxide from `in situ' X-ray diffraction measurements. Three kinds of sample have been irradiated: sintered samples (L = 1μm), non-ground powders (L = 45 nm) and ground powders (L = 28 nm). A cubic to monoclinic phase transformation appears if the electronic energy loss of the incident particle is higher
than a threshold. The comparison between the different kinds of samples reveals that this phase transformation is all the
easier as the mean crystallite size of the target is weak.
Received 27 January 2000 and Received in final form 13 December 2000 相似文献
9.
A.L. Balandin Y. Ono T. Tawara 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(1):97-103
A novel three-dimensional (3-D) tomography software has been developed for spherical tokamak (ST) plasmas with thin central
coils. It enables us to measure whole 3-D annular profiles of ST plasma emissivity (line spectrum etc.) using limited number
of detectors located on a sphere outside of its separatrix. The numbers and positions of detectors have been optimized for
STs that contain low-n toroidal modes from n = 1 to 5. Mathematical method allowing for the removal of the thin central coil from the region of reconstruction and to
reconstruct STs with single and double axes are also discussed. The shadow effect of center coil region was found to limit
the reconstruction accuracy, indicating that the low-aspect ratio torus (ST) is essential to this new 3-D tomography diagnostics.
Received 17 August 2000 and Received in final form 16 November 2000 相似文献
10.
R.R. Netz 《The European physical journal. E, Soft matter》2001,5(2):189-205
Using a field-theoretic formalism, we calculate the static contribution to the van der Waals interaction between two dielectric
semi-infinite half-spaces in the presence of mobile salt ions. The ions can be located in the slab, in one, or in both half-spaces.
We include an excess polarizability of the salt ions, i.e., each (spherical) ion has a dielectric constant which in general is different from the surrounding medium. This leads to
a modification of the effective dielectric constant of the medium hosting the ions. This shift can be large for high salt
concentrations and therefore influences the Hamaker constant decisively. Salt ions in the slab screen the static van der Waals
interaction, as was shown by Davies and Ninham. The salt-modified van der Waals interaction also contains salt-confinement
and salt-correlation effects. This is clearly demonstrated by the fact that the interaction is non-zero even in the case when
the dielectric constant is homogeneous throughout the system, in which case salt correlations are solely responsible for the
interaction. If the salt ions are in one or both of the two half-spaces (and no ions in the slab), the van der Waals interaction
is not screened but the effective Hamaker constant approaches a universal value for large slab thickness which is different
from the value in the absence of salt ions and which is independent of the salt concentration and of the effective electrolyte
dielectric constant. If both half-spaces contain salt, the asymptotic value of the Hamaker constant for large separation between
the half-spaces is the one obtained for the interaction between two metallic half-spaces through an arbitrary dielectric medium,
which is given by A≃ - 1.20. As is explicitly demonstrated, ion enrichment or depletion at the interfaces due to image-charge effects is already
included on the one-loop level and therefore does not lead to a change of the screened van der Waals interaction as given
by Davies and Ninham. For positive and negative ions with different valencies or different excess polarizabilities, we obtain
different adsorbed surface excesses of positive and negative ions, leading to a non-vanishing surface potential, which is
computed explicitly. All of these results are obtained on the linear one-loop level. For a special case we extend the calculation
of the dispersion interaction to the two-loop level. We find the corrections to the one-loop results to be quite large for
high salt concentrations or multivalent ions.
Received 17 February 2000 相似文献
11.
N. Neskovic S. Petrovic L. Zivkovic 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(4):553-558
This study is devoted to the transmission of Ne10+ ions through a Si thin crystal. The ion energy is 60 MeV and the crystal thickness is varied from 159 to 478 atomic layers, i.e. within the first rainbow cycle. The analysis is performed by the theory of crystal rainbows. The angular distribution of
the transmitted ions is generated by the computer simulation method. Then, the rainbow lines in the scattering angle plane
are determined. These lines ensure the full explanation of the angular distribution.
Received 11 May 2000 相似文献
12.
T. Fritioff C. Carlberg G. Douysset R. Schuch I. Bergström 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,15(2):141-143
The atomic and nuclear masses of 4He and 3He have been measured using doubly charged ions in a Penning trap connected to an electron beam ion source. Recent technical
improvements allow mass determinations with uncertainties of a few parts in 1010. The obtained atomic masses are 4.002 603 256 8(13) u and 3.016 029 323 5(28) u respectively. These values deviate by as
much as 5 standard deviations from the accepted values.
Received 23 October 2000 and Received in final form 6 February 2001 相似文献
13.
D. Zanghi A. Traverse J.-P. Dallas E. Snoeck 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(1):171-179
Ni ions were implanted in bulk AlN with the goal to form embedded metallic clusters. Combining several characterisation techniques
such as X-ray absorption spectroscopy, X-ray diffraction and high resolution transmission electron microscopy, we determined
the lattice parameter of the Ni clusters that display a fcc crystalline structure. The average size increases when the ion
fluence is increased or after a thermal treatment. Thanks to moiré fringes observed by high resolution transmission electron
microscopy and to satellite peaks seen on the diffraction patterns, we concluded that the annealed Ni clusters orientate their
(002) planes on the (101) of AlN. Moreover, the satellite positions allowed us to calculate Ni cluster average diameters,
that are in agreement with average sizes deduced by X-ray absorption spectroscopy.
Received 25 August 1999 and Received in final form 8 February 2000 相似文献
14.
J.C. Pickering V. Zilio 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(2):181-185
High resolution spectra of neutral silver have been recorded by Fourier Transform Spectrometry in the region 2 000-8 280 ?(50
000-12 000 cm-1) with silver-neon and silver-argon hollow cathode lamps as sources. This work represents order-of-magnitude improvements,
compared to previous work on Ag I, in accuracy of transition wavelengths and wavenumbers, and energy level values. 35 classified
Ag I transitions are given, and the wavenumber uncertainty for the strongest lines is less than 0.002 cm-1. Improved values for 28 energy levels are presented.
Received 31 January 2000 and Received in final form 13 June 2000 相似文献
15.
Z.W. Shen T. Chen M. Heid W. Kiefer V. Engel 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(2):167-172
We present simulations on pump-dump-probe experiments performed on the potassium dimer. The interaction of two time-delayed
laser pulses prepares vibrational wave packets in the electronic ground state. The quantum calculations reveal to what extent
it is possible to prepare a ground state superposition of states with high versus low vibrational quantum numbers by changing the pump-dump delay time. It is shown that transient signals may exhibit interference
effects which are due to characteristics of ground state wave-packets composed of two components showing different vibrational
dynamics. In this way the signals are able to yield information about vibrational overtone motion.
Received 27 September 2000 and Received in final form 21 November 2000 相似文献
16.
N.L. Tsintsadze P.K. Shukla L. Stenflo 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(1):109-115
The electroweak coupling between intense neutrino beams and strongly degenerate relativistic dense electron-positron magnetoplasmas
is considered. The intense neutrino bursts interact with the plasma due to the weak Fermi interaction force, and their dynamics
is governed by a kinetic equation. Our objective here is to develop a kinetic equation for a degenerate neutrino gas and to
use that equation to derive relativistic magnetohydrodynamic equations. The latter are useful for studying numerous collective
processes when intense neutrino beams nonlinearly interact with degenerate, relativistic, dense electron-positron plasmas
in strong magnetic fields. If the number densities of the plasma particles are of the order of 1033 cm-3, the pair plasma becomes ultra-relativistic, which strongly affects the potential energy of the weak Fermi interaction. The
new system of equations allows several neutrino-driven streaming instabilities involving new types of relativistic Alfvén-like
waves. The relevance of our investigation to the early universe and supernova explosions is discussed.
Received 11 September 2002 Published online 4 February 2003
RID="a"
ID="a"Permanent address: Department of Physics, Tbilisi State University, Chavchavadze 3, Tbilisi 38028, Georgia.
RID="b"
ID="b"Also at the Department of Plasma Physics, Ume? University, 90187 Ume?, Sweden; and the Center for Interdisciplinary Plasma Science,
Max-Planck Institut für Plasmaphysik und extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany. e-mail: ps@tp4.ruhr-uni-bochum.de
RID="c"
ID="c"Permanent address: Department of Plasma Physics, Ume?University, 90187 Ume?, Sweden. 相似文献
17.
H.-K. Kim E. Tuite B. Nordén B.W. Ninham 《The European physical journal. E, Soft matter》2001,4(4):411-417
The source of the activation energy that allows cutting of DNA by restriction enzymes is unclear. A systematic study of the
cutting efficiency of the type-II restriction endonuclease EcoRI, with varying background electrolyte ion pair and buffer reported here, shows only a modest dependence of efficiency on
cation type. Surprisingly, efficiency does depend strongly on the presumed indifferent anion of the background salt. What
emerges is that competition between the background salt anion and the buffer anion for the enzyme and DNA surfaces is crucial.
The results are unexpected and counterintuitive from the point of view of conventional electrolyte theory. However, taken
together with recent developments in surface chemistry, the results do fall into place and could also suggest a novel mechanism
for enzyme activity as an alternative to metal-activated hydrolysis: microscopic cavitation in a hydrophobic pocket might
be the source of activation energy.
Received 19 June 2000 and Received in final form 17 October 2000 相似文献
18.
R. Parajuli S. Matt O. Echt A. Stamatovic P. Scheier T.D. Märk 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):69-72
We have carried out measurements on metastable fragmentation of mass selected argon cluster ions which are produced by electron
impact ionization of a neutral argon cluster beam. From the shape of the fragment ion peaks (MIKE scan technique) one can
deduce information about the distribution of kinetic energy that is released in the decay reaction. In this study, for Ar
5
+ to Ar
15
+, it is Gaussian and thus we can calculate from the peak width the mean kinetic energy release 〈KER〉 of the corresponding
decay reactions. Using finite heat bath theory we calculate from these data the binding energies of the decaying cluster ions.
Received 20 November 2000 相似文献
19.
A. Fnidiki F. Studer J. Teillet J. Juraszek H. Pascard S. Meillon 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(3):291-295
The behavior of the magnetic properties of magnetite Fe3O4 irradiated by swift heavy ions is investigated by magnetization measurements. Although there is no induced structural phase
transformation, both coercive field and saturation magnetization are sensitive to ion irradiation and exhibit different behaviors
depending on the ion fluence range. In the low fluence regime, the coercive field increases, which is evidence for a strong
pinning of magnetic domain boundaries by the induced defects. The magnetization shows a decrease in the saturation value and
tends to reorient perpendicularly to the ion track axis. At high fluence, the initial magnetic properties of the sample are
nearly restored. The changes in the magnitude and the direction of magnetization are interpreted by magnetostrictive effects
related to the stress induced by irradiation. A phenomenological model is applied to reproduce the fluence evolution of the
saturation magnetization, assuming relaxation of the stress induced around the core of defects of the tracks by overlapping
effects at high fluence. The results are compared to those obtained in the case of yttrium iron garnet Y3Fe5O12.
Received 18 April 2001 and Received in final form 24 July 2001 相似文献
20.
U. Kentsch T. Werner G. Zschornack F. Grossmann V.P. Ovsyannikov F. Ullmann 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,17(3):297-305
Irq+ ( 41≤q≤64) ions with open-shell configurations have been produced in the electron beam of the room-temperature Dresden Electron
Beam Ion Trap (Dresden EBIT) at electron excitation energies from 2 keV to 13 keV. X-ray emission from direct excitation processes
and radiative capture in krypton-like to aluminium-like iridium ions is measured with an energy dispersive Si(Li) detector.
The detected X-ray lines are analyzed and compared with results from multiconfigurational Dirac-Fock (MCDF) atomic structure
calculations. This allows to determine dominant produced ion charge states at different electron energies. The analysis shows
that at the realized working gas pressure of 5×10-9mbar for higher charged ions the maximum ion charge state is not preferently determined by the chosen electron beam energy
needed for ionization of certain atomic substates, but by the balance between ionization and charge state reducing processes
as charge exchange and radiative recombination. This behaviour is also discussed on the basis of model calculations for the
resulting ion charge state distribution.
Received 12 July 2001 and Received in final form 10 September 2001 相似文献