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1.
Electron impact double ionization cross-sections for Ba and Ba+ have been calculated in the binary encounter approximation. Hartree-Fock velocity distribution has been used for the first
ejected electron and a hydrogenic velocity distribution for the second. For Ba+ the focusing effects of the target ion on the incident electron have been incorporated in the calculations. Contributions
from ionization-autoionization to the ionization cross-sections, as observed in experiments, have been included in the present
work. The calculated results show structures as observed in recent experiments. 相似文献
2.
L. K. Jha B. N. Roy 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,37(1):51-57
Electron impact double ionization cross-sections for Fe+ and Fe3+ have been calculated in the modified binary encounter
model incorporating the effects of the Coulombic field of the target on the
incident electron. Accurate expression of cross-section for energy
transfer ΔE given by Vriens and Hartree-Fock velocity distributions for the target electrons have been used throughout the
calculations. The present results show satisfactory agreement with
experimental observations. It is concluded that the discrepancy in the high
energy region observed in the present calculations may be attributed to non-inclusion of indirect ionization processes arising
from the L-shell. 相似文献
3.
H. Deutsch K. Becker P. Defrance M. Probst J. Limtrakul T. D. Märk 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(3):489-493
New measurements of the cross-section for electron impact ionization of the
molecular ion C2H2+ have been carried out recently. These
data differ significantly from earlier data, because cross-sections
corresponding to all the possible dissociative ionization processes were
determined. The new data in conjunction with the significant discrepancies
between the earlier data and the results of various calculations, which
disagreed among themselves by a factor of 3, motivated a renewed attempt to
apply the semi-classical Deutsch-M?rk (DM) formalism to the calculation
of the absolute electron-impact ionization cross-section of this molecular
ion. A quantum chemical molecular orbital population analysis for both the
neutral molecule and the ion revealed that in the case of
C2H2+ the singly occupied molecular orbital (i.e. the
“missing” electron) is highly localized near the site of a C atom in the
molecule. This information is explicitly incorporated in our formalism. The
results obtained by taking the ionic character directly into account are in
excellent agreement with the recent experimental data. 相似文献
4.
N. Kishimoto M. Matsumoto E. Matsumura K. Ohno 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(1):75-84
Stereodynamics in ionization of toluene and o-, p-chlorotoluenes by collision
with He*(23S) metastable atoms were investigated by two-dimensional
collision-energy/electron-energy-resolved Penning ionization electron
spectroscopy. Anisotropic interactions around the molecule were studied by
the collision energy dependence of partial ionization cross-sections
(CEDPICS) as well as model potential calculations, and shielding effect by
the methyl group was observed in CEDPICS for ionization from Cl lone-pair
orbitals of o-
chlorotoluene. Attractive interaction with He*(23S)
around the π orbital region was found to be larger for toluene rather
than o-, p-
chlorotoluenes. Exterior electron density (EED) calculation of
partial ionization cross-sections in Penning ionization and negative CEDPICS
for ionization band observed in ca. 4 eV in electron energy indicated that
π-2π+1 shake-up state was observed in
Penning ionization electron spectroscopy of toluene. 相似文献
5.
S. Kumari L. K. Jha B. N. Roy 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,55(1):93-97
Electron impact double ionization cross-sections of Sc+ions have been
calculated in the binary encounter approximation (BEA). Accurate expression
of σΔE(cross-section for energy transfer ΔE) and
Hartree-Fock velocity distributions for the target electrons have been used
throughout the calculations. Direct double ionization from ejection of 3d
and 4s electrons has been investigated in the modified double binary
encounter model incorporating the focusing action of the target ion on the
incident electron. The identification of the 3p shell whose ionization
provides a major contribution to double ionization through
ionization-autoionization is an interesting aspect of the present
investigation. The theoretical results show satisfactory agreement with the
experimental observations. 相似文献
6.
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
7.
In this paper we report our calculations on several important total cross-sections (TCSs) of positron impact on isoelectronic
N2 and CO molecules, treated in the complex spherical potential formalism. Basically the total (complete) cross-section Q
T consists of elastic and inelastic contributions. Our total inelastic cross-section (Q
inel) contains ionization and electronic excitations together with positronium formation. Our goal here is to bifurcate Q
inel further to deduce total ionization cross-section, using the ‘complex scattering potential–ionization contribution’ (CSP-ic)
method of electron–atom/molecule scattering. The present range of positron energy is 15–2000 eV. All the resulting cross-sections
are in a good general accord with the existing data. This work highlights the importance of various scattering channels in
e + -N2 and e + -CO interactions at intermediate and high energies. 相似文献
8.
《Journal of Electron Spectroscopy and Related Phenomena》2005,142(3):283-293
Collision-energy/electron-energy-resolved two-dimensional Penning ionization electron spectroscopy (2D-PIES) has been used to study outer characteristics of molecules. Anisotropic potential energy surfaces for collisional ionization of molecules with a metastable helium atom He*(23S) have been determined starting from ab initio model potentials via optimization based on trajectory calculations. Since ionization widths in the theoretical model of Penning ionization are functionals of target molecular orbitals, outer electron distributions of molecular orbitals can be determined via optimization procedures of calculated ionization cross-sections by trajectory calculations with respect to observed 2D-PIES data. 相似文献
9.
The differential angular cross section for single ionization of He in collisions with H+, D+, and T+ has been calculated within the framework of the three-body approximation. The results of the calculations of the angular
distribution of H+, D+, and T+ are compared with the available experimental and calculational data.
Translated from a manuscrip submitted December 10, 1996. 相似文献
10.
A new parameterization scheme is proposed for valence electron calculations which employ the pseudopotential formalism. This scheme has been implemented in calculations for Fe, Fe+, Fe2+, Fe3+ and FeH+. In comparison with conventional all-electron calculations the errors are of the order of 1 per cent in valence orbital energies, 0·5 per cent in ionization energies and 2 per cent in the molecular binding energy. Detailed comparisons are made between the present method, which is formulated in terms of orbital projection operators, and recent calculations based on local, angular momentum dependent, effective potentials. The two approaches are found to be capable of almost equal accuracy. 相似文献
11.
James A.R. Samson J.L. Gardner 《Journal of Electron Spectroscopy and Related Phenomena》1976,8(1):35-44
The absolute values of the partial photoionization cross-sections and branching ratios for producing carbon monoxide ions in their X2Σ+, A2Π, B2Σ+ and 2Σ+(σ2s) states have been obtained as a function of wavelength from the A2Π ionization threshold to 304 Å. Results have been obtained within autoionizing resonances as well as within the photoionization continuum. 相似文献
12.
N. Brown 《Zeitschrift fur Physik C Particles and Fields》1991,51(1):107-112
We describe the calculation of five jet production from theW
+
W
– intermediate state ine
+
e
– annihilation in lowest order QCD. Some results for integrated cross-sections are presented. 相似文献
13.
A new Coulomb distorted-wave method with coupled-channel target functions is used to calculate total ionization cross-sections for helium in positron collisions. Besides Slater-like orbitals we use regular Coulomb wave packets in our configurational interaction basis to describe the target continuum. The incident positron energy was varied between the ionization threshold and 500 a.u. The results are in good agreement with experimental data and other theoretical calculations. Comparing to other sophisticated distorted wave methods our model is much easier to implement and gives accurate results. As a new feature we present ionization cross-sections where the He + ion remains in the 1s ground state or excited to the 2s or 2p state. As we know there are no experimental work done to determine such cross-sections. In the case of ionization followed by 2s or 2p excitation we compared our results with other calculations.Received: 18 February 2004, Published online: 15 April 2004PACS:
34.85. + x Positron scattering 相似文献
14.
《Surface science》1995,324(1):L349-L354
The mechanism of neutralization of and negative ionization from hydrogen ions is studied via experiments in which H+ beams are incident on LiCl surfaces, combined with molecular-orbital-energy calculations. It is found that charge transfer and electron excitation occur due to the resonant-tunneling and electron-promotion mechanisms via a short-lived chemisorption state of hydrogen. The probability for H+ to H− conversion at the LiCl surface depends on the species of the target atoms and is enhanced in collision with Li+ by one order of magnitude relative to Cl−. 相似文献
15.
Heavy-ion fusion below the Coulomb barrier: The systems 28,30Si + 58,62,64Ni and 32,34,36S + 58,64Ni
《Nuclear Physics A》1986,456(3):509-534
Fusion cross-sections for the 12 systems 28,30Si + 58,62,64Ni and 32,34,36S + 58,64Ni were measured at many energies from well below up to about 1.5 times the Coluomb barriers. The data show large sub-barrier fusion probabilities with strong isotopic dependences. The results of coupled-channel calculations involving the lowest 2+ and 3− levels of both colliding nuclei and the 2-neutron transfer channel are compared with the measured excitation functions. Indications for the importance of the transfer channels are found. Signatures of system-dependent effects of the positive Q-value transfer channels are evidenced, also from a systematic intercomparison of the data. 相似文献
16.
J. Lecointre D. S. Belic J. J. Jureta R. K. Janev P. Defrance 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,55(3):569-580
Absolute cross-sections have been measured for electron-impact dissociative
excitation and ionization of CD2+ leading to
formation of CD22+, CD+, C+,
D2+ and D+. The animated crossed-beams method
is applied in the energy range from the reaction threshold up to 2.5 keV.
The maximum total cross-sections are found to be (1.2±0.1)×10-17 cm2, (6.1±0.7)×10-17 cm2, (6.4±0.7)×10-17 cm2, (26.3±3.8)×10-19 cm2 and (14.9±1.4)×10-17 cm2 for
CD22+, CD+, C+,
D2+ and D+ respectively. Individual
contributions for dissociative excitation and dissociative ionization are
determined for each singly-charged product, which are of significant
interest in fusion plasma edge modelling and diagnostics. Conforming to the
scheme recently applied in the CD4+ and in the
CD3+ articles, the cross-sections are presented in
closed analytic forms convenient for implementation in plasma simulation
codes. Kinetic-energy-release distributions are determined for each ionic
fragment at selected electron energies. 相似文献
17.
Experimental study of cross-section ratios in the collisions of Cq+ and oq+(q= 1-4) on atomic helium in strong-interaction region
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We have measured the cross-section ratios of helium induced by Cq+ and Oq+ (q=1-4) in an energy range from 20 keV/amu to 500 keV/amu, and obtained the two-dimensional spectra by employing the coincidence method combined with the MPA-3 data acquisition system. Hence, we obtain the ratios of total single-ionization cross-sections (SI, SC, SLSI, and DLSI), total double-ionization cross-sections (DI, DC, TI, SLDI, and DLDI) and cross-sections of every process (SI, SC, SLSI, DLSI, DI, DC, TI, SLDI, and DLDI), which induce the single-ionization and double-ionization, to the total cross sections respectively. The competitive relations between the reaction-channels and the experimental data law of each reaction-channel are revealed explicitly, and the qualitative explanations involved in those results are also presented accordingly. 相似文献
18.
A new microscopical quantum-mechanical model of ionization of sputtered particles is described which takes into account electron excitations due to the atomic motions in the substrate. The substrate is represented by a simple atomic, metal-like, chain. Numerical calculations yield ionization probabilities R+ which have magnitudes close to the experimental values and have realistic velocity dependence. The function of R+ versus the sputtered atom ionization energy can be well approximated by the Maxwell-Boltzmann law with an effective temperature of about 3500 K. 相似文献
19.
A. Arima N. Yoshinaga Y.M. Zhao 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):105-107
We investigate the dominance of 0+ states as the lowest states in shell model calculations with random two-body interactions in a single j-shell. We have found an explanation of the large probability of the 0+ ground state.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
20.
The data for the total cross-section ofK
+
scattering on various nuclei have been analysed in the Glauber multiple scattering theory. Energy-dependentK
+
-nucleus optical potential is generated using the forwardK
+
-nucleon scattering amplitude and the nuclear density distribution. Along with this, the calculated totalK
+
-nucleus cross-sections using the effectiveK
+
-nucleon crosssection inside the nucleus are also presented. 相似文献