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1.
Configuration-average distorted-wave calculations are carried out for electron-impact ionization of Ar5+. Both direct ionization and the indirect excitation autoionization processes are included in our calculations. Our theoretical values are in quite reasonable agreement with the experimental data. The indirect processes contribute up to 50% to the total ionization cross sections. The possible origin of double-hump resonance structure of the cross sections is demonstrated and the contributions of metastable states are also taken into account. 相似文献
2.
Configuration-average distorted-wave calculations are carried out for electron-impact ionization of Ar^5 + .Both direct ionization and the indirect excitation autoionization processes are included in our calculations. Our theoretical values are in quite reasonable agreement with the experimental data. The indirect processes contribute upto 50% to the total ionization cross sections. The possible origin of double-hump resonance structure of the crcessections is demonstrated and the contributions of metastable states are also taken into account. 相似文献
3.
M. R. Talukder 《Applied physics. B, Lasers and optics》2008,93(2-3):567-574
A simple user-friendly empirical formula is proposed to calculate the electron impact total single ionization cross sections of beryllium-like Be, B+, C2+, N3+, O4+, Ne6+, Fe22+, Hg76+, and U88+ and boron-like B, C+, N2+, O3+, Ne5+, Fe21+, Kr31+, and Xe49+ targets. A simplified and modified version of the Bell formula is used in the present model incorporating the ionic correction factor. The predicted ionization cross sections are compared with the available experimental and theoretical results. Excellent agreements are found for the incident energies ranging from threshold to 106 eV considered herein. The presented results achieve a level of agreement that is better than the calculations from the existing theoretical methods and empirical models. Hence, this model may be an excellent choice, due to its simplicity, for the practitioners in the fields of applied sciences and technologies. 相似文献
4.
Total cross sections (TCSs) for electrons scattering from molecules over a wide energy range are widely used in gaseous lasers, astrophysics, plasma physics, atmospheric physics, and chemical physics, etc.. TCS values repro- duced by analytical or empirical expressions accurately are very useful in computational work related with these applications. Because electron-molecule scattering is a much more complex problem than the corresponding electron-atom scattering, in order to get more accura… 相似文献
5.
HU Wei WANG Yansen FANG Dufei LU Fuquan TANG Jiayong YANG Fujia 《Chinese Journal of Lasers》1994,3(3):223-230
ElectronimpactionizationcrosssectionsforLi-likeAlioningroundandexcitedstatesHUWei;WANGYansen;FANGDufei;LUFuquan;TANGJiayong;Y... 相似文献
6.
The dissociative ionization of CO2 induced by 5 keV electrons in two-body and three-body dissociative channels of CO2+2 and CO3+2 is identified by the ion-ion coincidence- method using a momentum imaging spectrometer. The partial ionization cross sections (PICSs) of different ionic fragments are measured and the results generally agree with the calculations made by a semi-empirical approach. Furthermore, the PICSs of the dissociative channels are also obtained by carefully considering the detection efficiency of the micro-channel plates and the total transmission efficiency of the time of flight system. 相似文献
7.
Ionization cross sections for electron scattering from metastable rare-gas atoms (Ne~* and Ar~*)
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The optical-model approach has been used to investigate the electron-impact ionization of metastable rare-gas atoms. A complex equivalent-local polarization potential is obtained to describe the ionization continuum channels. We have calculated the cross sections for collisional ionization of the metastable atoms Ne* and Ar* by electrons in the energy range from threshold to 200 eV. The present results are in agreement with the available experimental measurements and other theoretical calculations. 相似文献
8.
ABSTRACTStopping cross sections (SCS) for protons, alphas and Li ions are calculated with a modified form of our earlier work by incorporating a different electron density distribution of target materials; this involves four parameters – two projectile dependent and the rest two remain fixed. The prosed model has been tested for three stripped ion (H+, He2 + and Li3 +) projectiles and found that it describes quite satisfactorily the experimental SCS data from low energies with projectile velocities nearing v = Z1v0 (with Z1 as the atomic number and v0 the Bohr velocity) up to 100.0 MeV over a wide range of stopping media with atomic numbers Z2 =3–100. 相似文献
9.
The experimental data of Mαβ X-ray production cross sections for Pb and Bi by 9–40 keV electron impact have been given. Thin films with thick carbon substrates are used in the experiment. The effects of target structure on the Mαβ X-ray production cross sections are corrected by using the Monte Carlo method. The corrected experimental data are compared with calculated cross sections in terms of the distorted-wave Born approximation(DWBA) theory. The measured Mαβ X-ray production cross sections for Pb and Bi are lower than the DWBA calculations. The atomic relaxation parameters used in comparing the DWBA values with experimental results affect the degree of difference. 相似文献
10.
Differential, elastic integral and moment transfer cross sections for electron scattering from N2 at intermediate- and high-energies
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A complex optical model potential modified by incorporating the concept of bonded atom, with the overlapping effect of electron clouds between two atoms in a molecule taken into consideration, is firstly employed to calculate the differential cross sections, elastic integral cross sections, and moment transfer cross sections for electron scattering from molecular nitrogen over the energy range 300—1000eV by using additivity rule model at Hartree—Fock level. The bonded-atom concept is used in the study of the complex optical model potential composed of static, exchange, correlation polarization and absorption contributions. The calculated quantitative molecular differential cross sections, elastic integral cross sections, and moment transfer cross sections are compared with the experimental and theoretical ones wherever available, and they are found to be in good agreement with each other. It is shown that the additivity rule model together with the complex optical model potential modified by incorporating the concept of bonded atom is completely suitable for the calculations of differential cross section, elastic integral cross section and moment transfer cross section over the intermediate- and high-energy ranges. 相似文献
11.
A modification potential method of calculating total cross sections of electrons scattering from complex molecules C2H6, C2F6, C6H6 and C6F6 at 100 eV-5000 eV
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A complex optical model potential modified by
incorporating the concept of bonded atom, which takes into consideration the
overlapping effect of electron clouds between two atoms in a molecule, is
first employed to calculate the total cross sections for electrons
scattering from such complex molecules as C总交叉断面 电子散射 添加规则 原子分子碰撞 电子云 total cross section, electrons scattering, additivity
rule, atomic and molecular collision Project supported by the National Natural Science Foundation of China (Grant No 10574039). 2005-11-10 2005-11-102005-11-30 A complex optical model potential modified by incorporating the concept of bonded atom, which takes into consideration the overlapping effect of electron clouds between two atoms in a molecule, is first employed to calculate the total cross sections for electrons scattering from such complex molecules as C2H6, C2F6, C6H6 and C6F6 using the aclditivity rule model at Hartree-Fock level over the energy range from 100 eV to 5000 eV. The total cross sections are quantitatively compared with those obtained by experiments wherever available, and they are in good agreement with each other over a wide energy range. It is shown that the modified potential together with the additivity rule model is completely suitable for the calculation of total cross sections of electrons scattering from such complex molecules as C2H6, C2F6, C6H6 and C6F6 above 200 eV-300 eV. 相似文献
12.
We report calculated total elastic cross sections Qel, total ionisation cross sections, Qion, summed total excitation cross sections ∑Qexc and total cross sections QT for CH3SH upon electron impact for energies from ionisation threshold to 5 keV. We have employed Spherical Complex Optical Potential (SCOP) formalism to calculate total elastic cross section Qel, and total inelastic cross section Qinel and used Complex Scattering Potential – the ionisation contribution (CSP-ic) method to extract the ionisation cross sections, Qion, from the calculated Qinel. The calculated total cross sections are examined as functions of incident electron energy and are compared with available data wherever possible and overall good agreement is observed. In this work Qel, Qion, and ∑Qexc are reported for the first time for CH3SH in this energy range. 相似文献
13.
A model complex optical potential rewritten by the conception of bonded atom, which considers the overlapping effect of electron cloud, is employed to calculate the total (elastic + inelastic) cross sections with simple molecules (N2, O2, NO2, NO, N2O) consisting of N & O atoms over an incident energy range of 100 - 1600 eV by the use of additivity rule at Roothaan-Hartree-Fock level. In the study, the complex optical potential composed of static, exchange, correlation polarization plus absorption contributions firstly uses bonded-atom conception. The qualitative results are compared with experimental data and other calculations wherever available and good agreement is obtained. The total cross sections of electron-molecule scattering above 100 eV can be successfully calculated. 相似文献
14.
15.
《Surface science》1986,171(1):55-68
A dynamical LEED intensity analysis is reported for Cu(001)−c(2 × 2)-Pb. The adsorbate layer distance from the substrate is determined as 2.29 Å, and the topmost interlayer spacing for the substrate is the same as in bulk Cu, in contrast to a contraction for clean Cu(001). This structural result is, within the accuracy reached, insensitive to changes in the assumed scattering potential models. The r-factors suggest a weak preference for an energy-dependent exchange correlation and a moderate one for adding a localized adsorption part inside the muffin-tin spheres. The sensitivity of spectra and r-factors to changes in the assumed isotropic Debye temperature for Pb suggests that vibrational anisotropy should be taken into account in order to improve the accuracy of the analysis. Calculated spin polarization spectra are very sensitive to the exchange approximation, the localized absorption and the Debye temperature. Together with experimental data, they should be useful in particular for determining the vibrational anisotropy. 相似文献
16.
Absolute cross sections of electron attachment to molecular clusters: Part I. Formation of (CO2)
N
−
A procedure of determining absolute cross section σ? of electron attachment to (CO2)N clusters at pair collisions in crossed beams is suggested. The cross section is measured as a function of energy (E = 0.1–50 eV) and of cluster mean size N in a beam $(\bar N = 2 - 4000 molecules)$ . It is found that, even at $\bar N > 200$ and E ≤ 3 eV, σ? is equal to, or larger than, 7 × 10?13 cm2, i.e., by more than one order of magnitude exceeds the maximal cross section of CO2 ionization by electron impact. The dependences σ? $(\bar N,E)$ have two wide continua at E ≤ 5.2 eV and E ≥ 6.9 eV, which correlate well with known functions of CO2 electron-impact-induced excitation. These continua are attributed largely to formation of (CO2) N ? ions during electron thermalization and solvation in the clusters. At E → 0, the polarization capture of an incident electron by the cluster leads to a sharp increase in cross section σ?(E). From the dependences σ? $(\bar N,E)$ measured, the thermalization and sovation probabilities for electrons with E ≤ 0.8 eV and the rate of electron energy loss in the cluster are found. 相似文献
17.
Jeremy J. Harrison Nicholas D.C. Allen Peter F. Bernath 《Journal of Quantitative Spectroscopy & Radiative Transfer》2011,112(1):53-58
Infrared absorption cross sections for acetone (propanone), CH3C(O)CH3, have been determined in the 3 μm spectral region from spectra recorded using a high-resolution FTIR spectrometer (Bruker IFS 125 HR) and a multipass cell with a maximum optical path length of 19.3 m. The spectra of mixtures of acetone with dry synthetic air were recorded at 0.015 cm−1 resolution (calculated as 0.9/MOPD using the Bruker definition of resolution) at a number of temperatures and pressures (50-760 Torr and 195-296 K) appropriate for atmospheric conditions. Intensities were calibrated using three acetone spectra (recorded at 278, 293 and 323 K) taken from the Pacific Northwest National Laboratory (PNNL) IR database. 相似文献
18.
S. S. Arzumanov L. N. Bondarenko P. Geltenbort V. I. Morozov Yu. N. Panin S. M. Chernyavsky 《Physics of Atomic Nuclei》2008,71(11):1880-1886
The results obtained by measuring the cross sections for the inelastic scattering of very cold neutrons for a number of metals and polymers by the method of a neutron-irradiation analysis are presented. The method is based on simultaneously measuring events of inelastic scattering and neutron capture in the sample under investigation via recording gamma radiation with a semiconductor germanium detector. Neutron capture by a nucleus of the sample is accompanied by the prompt radiation of gamma rays having a known spectrum. Upon inelastic scattering, a neutron acquires thermal energy. Upon leaving the sample, this neutron is absorbed in a special converter that contains the isotope 10B. The capture of the neutron by a 10B nucleus is followed by the emission of a 477-keV gamma ray. The probabilities of capture and inelastic scattering are proportional to the respective neutron-interaction cross sections, and the ratio of the recorded detector counts corresponding to events of the two types does not depend on the spectrum of the incident flux of very cold neutrons or on the trajectory of neutron motion in the sample. The sought inelastic-scattering cross section at a fixed sample temperature is calculated by using this ratio and the known cross section for neutron capture by the sample isotope having a known gamma-radiation spectrum. 相似文献
19.
M. Das M. Purkait C. R. Mandal 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(1):13-18
The Classical Trajectory Monte-Carlo (CTMC) simulation method has been employed to calculate the total electron capture cross-sections
with sub-shell distributions and ionization cross-sections in collision of B
q+
(q=1-4) with ground state atomic hydrogen in the energy range of 10-200 keV/amu. The computed results have been observed to be in
reasonable agreement with other existing theoretical and experimental results over the entire energy region considered.
Received 23 February 1999 and Received in final form 23 May 1999 相似文献
20.
In this paper we derive the Θ production cross section in high energy proton-proton collisions in the relativistic framework through using effective hadronic couplings. Both the nucleon and N*(1710) propagations are taken into account in the intermediate states. The one π and one ρ exchange mechanisms are considered and the commonly accepted coupling constants and form factors are used in the calculation. We find that ρ exchange is dominant in these processes and the N*(1710) propagation in the intermediate state is important,which increases the Θ production cross section by a factor of a few tens at center of mass energy 4GeV. 相似文献