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1.
Spectroscopic studies of the production of MgII ions from atomic metastable states by electron impact in crossed atomic and electron beams were made. Cross sections for excitation of the strongest spectral transitions and their energy dependences were determined. The maximum value of the cross section for ionization with excitation of the 32 S 1/2–32 P 3/2 transition reached 2.4×10?16 cm2. Possible mechanisms of production of excited ions from metastable states and their contribution to the total ionization process are discussed. 相似文献
2.
M. Vinodkumar K. Korot P. C. Vinodkumar 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,59(3):379-387
In this article, we report calculations of total
ionization cross sections, Q
ion
, for simple atoms (C, N, O, F) and
molecules (NO and NH3)_{3}) of atmospheric interest on electron impact at
energies from threshold to 2000 eV. We have employed the complex scattering
potential – ionization contribution (CSP-ic) method for the present study.
Attempt has been made to improve the method by computing the parameter that
involves the ratio of sum of the total excitation cross sections
(Σ
Q
exc
) and total inelastic cross section (Q
inel
) at the peak of the
inelastic cross section. The present study not only provided a better
estimation of the parameter involved in the CSP-ic method but also provided
better agreement with the available experimental and theoretical data on the
ionization cross sections of the simple atomic and molecular targets studied
here. 相似文献
3.
M. Gupta K. L. Baluja 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(3):475-483
Electron-H2S collision process is studied using the R-matrix method. Nine low-lying states of H2S molecule are considered in the R-matrix formalism to obtain elastic integral, differential, momentum transfer and excitation cross sections for this scattering
system. We have represented our target states using configuration interaction (CI) wavefunctions. We obtained adequate representation
of vertical spectrum of the target states included in the scattering calculations. The cross sections are compared with the
experiment and other theoretical results. We have obtained good agreement for elastic and momentum transfer cross sections
with experiment for entire energy range considered. The differential cross sections are in excellent agreement with experiment
in the range 3–15 eV. A prominent feature of this calculation is the detection of a shape resonance in 2B2 symmetry which decays via dissociative electron attachment (DEA). Born correction is applied for the elastic and dipole allowed
transition to account for higher partial waves excluded in the R-matrix calculation. The electron energy range is 0.025–15 eV. 相似文献
4.
In the framework of the Multi-Channel Quantum Defect Theory (MQDT), a theoretical study of the dissociative excitation is
presented. Numerical results for the dissociative excitation cross sections of HD
+, D
2+, and DT
+ with electrons of energy between 2 and 12 eV are reported. The contribution of the vibrational continua of the two lowest
electronic states as explicit ionization channels has been considered. Within a quasi-diabatic representation of the molecular electronic states, the Born expansion of second order is done in the K-matrix evaluation. 相似文献
5.
J. Mahoney V. Tarnovsky K. H. Becker 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(2):289-293
We measured absolute partial cross sections for the formation of all singly
charged positive ions produced by electron impact on SiCl2 and SiCl
from threshold to 200 eV using the fast-neutral-beam technique. Some of the
cross section curves exhibit an unusual energy dependence with a pronounced
low-energy maximum at an energy around 30 eV, which may be indicative of the
presence of indirect ionization channels. Dissociative ionization channels
are dominant for both species. The experimentally determined total single
ionization cross sections for both species agree very well with calculated
cross sections using the Deutsch-M?rk (DM) formalism. A brief summary of
the ionization cross sections determined for all four SiClx (x=1–4)
species is given highlighting similarities and differences. 相似文献
6.
We describe the methods and the results of investigation of the yield of positive ions formed as a result of electron-impact ionization of sulfur. The ionization energy for the basic molecule and the energies corresponding to the emergence of fragment ions are obtained from the ionization efficiency curves. The dynamics of formation of molecular sulfur ions in the temperature range 320–700 K is investigated. The energy dependences of efficiency S n of the ion formation for n = 1–6 are analyzed, and their appearance energies are determined. The total cross section of sulfur ionization by a monochromatic electron beam is also investigated. Using the linear approximation method, we marked out features on the ionization function curve, which correspond to the ionization and excitation energies for multiply charged ions. The total cross section of the formation of negative sulfur ions is measured in the energy range 0–9 eV. 相似文献
7.
R. A. Fedorko T. A. Snegurskaya N. A. Margitich I. I. Shafranyosh 《Optics and Spectroscopy》2010,109(3):325-329
By means of the optical method using the technique of crossed electron and atomic beams, we obtained the absolute values of
the excitation cross sections of metastable cadmium atoms and their energy dependences. The absolute cross section values
reach ∼10−16 cm2 (at 30 eV). Sharp resonance-like maxima are observed in the energy dependences of the excitation cross section near the excitation
thresholds, which are supposedly related to the formation and decay of negative-ion excited states of. 相似文献
8.
An experimental technique for measuring the cross sections of direct and dissociative ionization of N2, O2, H2O, and CO2 molecules by electron impact in the near-threshold energy range is described. The setup used in the experiments allows mass
separation of ions with a monopole mass spectrometer. It is shown that such a setup can be used to advantage in separation
experiments. For incident electron energies between 7 and 35 eV, the energy dependences of the cross sections of generation
of parent ions and ion fragments due to parent molecule dissociation are obtained. 相似文献
9.
A. I. Mikhailov I. A. Mikhailov 《Journal of Experimental and Theoretical Physics》1999,89(6):1023-1029
Double ionization and excitation ionization in Compton scattering for heliumlike ions in metastable states are investigated.
The electron energy distribution for double ionization and the total cross sections for both processes are calculated. The
calculations are carried out in the zeroth order of perturbation theory with respect to electron-electron interaction, using
Coulomb wave functions as the first approximation. The resulting equations are valid only in the high-energy nonrelativistic
range. It is assumed that Z≫1, but αZ≪1 (Z is the charge of the nucleus, and α is the fine-structure constant).
Zh. éksp. Teor. Fiz. 116, 1889–1902 (December 1999) 相似文献
10.
The modified Jain–Khare semi-empirical formalism for the evaluation of differential and integral electron impact ionization cross sections for molecules has been extended to the evaluation of cross sections for the electron ionization of CO2 clusters: (CO2)240 and (CO2)1700. The energy dependent differential cross sections are evaluated at the incident electron energies of 50, 100 and 200 eV. The integral total ionization cross sections have been calculated in the energy range varying from ionization thresholds to 1000 eV which revealed a good agreement with the available experimental and the theoretical data. The ionization rate coefficients have also been evaluated using the presently calculated ionization cross sections and Maxwell–Boltzmann energy distributions. 相似文献
11.
A. A. Borovik 《Technical Physics》2012,57(8):1058-1061
The autoionization cross section of potassium atoms excited by electron impact is measured in the energy range from the first autoionization threshold at 18.72 eV to 202 eV. The data are obtained by deter-mining the total intensity of electron spectra resulting from the decay of the 3p 5 n 1 l 1 n 2 l 2 autoionizing states. The cross section has two maxima, 1.8 × 10?16 and 2.2 × 10?16 cm2, at 21 and 32 eV, respectively. The excitation dynamics of autoionization states suggests that the first maximum is associated with the resonance character of the near-threshold excitation. The second maximum, as well as the behavior of the cross section at energies above 50 eV, reflects the dynamics of electron excitation of quartet and doublet autoionizing states. The measured autoionization cross section is compared with known data for the total single ionization cross section of potassium atom by electron impact. The relative contribution of the autoionization cross section to the total single ionization cross section is found to reach 30% at 32 eV. 相似文献
12.
J. Lecointre H. Cherkani-Hassani S. Cherkani-Hassani D. S. Belic J. J. Jureta P. Defrance 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,60(2):331-345
Absolute cross sections for electron-impact single ionization, dissociative
excitation and dissociative ionization of the ethynyl radical ion
(C2D+)^+) have been measured for electron energies ranging from the
corresponding reaction thresholds to 2.5 keV. The animated crossed
electron-ion beam experiment is used and results have been obtained for the
production of C2D2+, C2+, C2+_2^+ , CD+, C+ and
D+. The maximum of the cross section for single ionization is found to
be (2.01 ± 0.02) × 10-17 cm2, at the incident electron
energy of 105 eV. Absolute total cross sections for the various singly
charged fragments production are observed to decrease by a factor of almost
three, from the largest cross-section measured for C+, over C2+_2^+
and CD+ down to that of D+. The maxima of the cross sections are
obtained to be (14.5 ± 0.5) × 10-17 cm2 for C2+_2^+,
(12.1 ± 0.1) × 10-17 cm2 for CD+, (27.7 ±
0.2) × 10-17 cm2 for C+ and (11.1 ± 0.8) × 10-17 cm2 for D+.
The smallest cross section is measured to
be (1.50 ± 0.04) × 10-18 cm2 for the production of the
doubly charged ion C2+. Individual contributions for dissociative
excitation and dissociative ionization are determined for each
singly-charged product. The cross sections are presented in closed analytic
forms convenient for implementation in plasma simulation codes. Kinetic
energy release distributions of dissociation fragments are seen to extend
from 0 to 6 eV for the heaviest fragment C2+_2^+, up to 11.0 eV for
CD+, 14.2 eV for C+ and 11.2 eV for D+ products. 相似文献
13.
Ionization cross sections of fragment ions of CF4, C2F6, C3F8, n-C4F10, C2F4, 1-C4F8, SiF4, COF2. CHF3 were determined in dependence on electron energy up to 125 eV by means of a quadrupol mass spectrometer. Tails at the low energy part of the characteristics are interpreted as a result of kinetic energy depending on molecular weight of fragments. Parent ions are only detected for chemically unsaturated compounds showing characteristic curves of ionization efficiency. Total cross sections obey the additive rule. 相似文献
14.
V. S. Vukstich E. Yu. Remeta N. M. Erdevdi O. B. Shpenik 《Optics and Spectroscopy》2008,104(4):524-533
The optical excitation functions (OEFs) for two series of spectral lines of the Cd atom originating from the 5sns 1 S 0 (n = 6?11) and 5snd 3 D 1, 2, 3 (n = 5 and 6) levels excited by an ultramonoenergetic (ΔE 1/2 < 0.05 eV) electron beam with energies exceeding the single ionization threshold are presented. In the energy range from 10.8 to 12.9 eV, the energy dependences of the excitation cross sections of the studied spectral transitions exhibit the effect of postcollision interaction of slow scattered and fast emitted electrons. This process leads to an additional population of the initial levels of the spectral transitions due to the capture of a scattered electron into an excited atomic level. The energies and widths of the electronic decay of autoionizing states are estimated in the classical approach by two methods, namely, by the least squares method and by direct calculation. Calculations are performed using approximate formulas valid for different relations between the postcollision shifts of the OEF maxima and the binding energies of the atomic levels. The terms of the autoionizing atomic states responsible for the maxima observed in the OEFs of the spectral transitions are determined. 相似文献
15.
We have measured the absolute values of the total cross section of the one-electron capture by He2+ ions in the kinetic energy range 2–30 keV at the Ar atoms. The absolute values of the differential scattering cross sections of He+ ions formed during the one-electron capture and the electron capture with ionization at energies of 2.2, 5.4, and 30 keV have been determined. The electronic states of the formed ions have been determined using collision spectroscopy based on analysis of the change in the kinetic energy of He+ after the interaction. We have measured doubly differential (with respect to the kinetic energy and the scattering angle) cross sections of the formation of free electrons. The free electron formation channels (direct ionization and electron capture with ionization) have been analyzed by calculating the electron terms of the (HeAr)2+ system. The calculated cross section of capture with ionization is in conformity with the cross section measured using collision spectroscopy. 相似文献
16.
V. V. Afrosimov A. A. Basalaev V. V. Kuz’michev M. N. Panov O. V. Smirnov 《Technical Physics》2016,61(3):342-348
The relative cross sections of elementary processes occurring in single collisions of tryptophan molecules in the gaseous phase with He2+ ions with energy 4 keV/u are measured using time-of-flight mass spectrometry for studying the mechanism of radiation damage of amino acid molecules. The fragmentation channels for intermediate singly and doubly charged tryptophan molecular ions formed during one-electron capture, two-electron capture, and electron capture with ionization are investigated. Significant difference is observed in the mass spectra of fragmentation of intermediate doubly charged ions formed during the capture with ionization and double capture, which is associated with different energies of excitation of {C11H12N2O2}2+* ions. 相似文献
17.
The methodology and results of mass-spectrometric studies of producing positive ions as a result of the dissociative ionization of a molecular selenium beam by electron impact are discussed. The appearance energies of fragment ions were determined from the ionization efficiency curves. The dynamics of production of molecular selenium ions in the temperature range of 420–500 K was also examined. The energy dependences of efficiency of production of singly charged Se n + ions for n = 1–4 and the doubly charged selenium ion in the interval from the threshold to 36 eV were studied for the first time. The observed specific features of effective ionization cross sections were analyzed. 相似文献
18.
E. É. Kontrosh I. V. Chernyshova L. Sovter O. B. Shpenik 《Optics and Spectroscopy》2001,90(3):339-343
The optical excitation functions of four spectral lines corresponding to the transitions from the 41 D 2, 53 S 1, 43 D j, and 61 S 0 levels of atomic Zn were investigated with an electron spectrometer of a new construction. For the first time, elastic scattering of slow electrons from the Zn ions at an angle close to 180° was studied. In the energy range under investigation (0–7 eV), both the optical excitation functions of atomic spectral lines and the differential cross section of elastic scattering manifested the resonant structure caused by the contribution of autoionization states of the atom. 相似文献
19.
The extended crossed beam method was used to measure the dissociative excitation cross sections in e-CoCl2 collisions for 91 transitions from odd doublet levels of cobalt atoms. The dissociative and direct CoI excitation cross sections
were compared. Possible reaction channels at low electron energies were considered. The results were used to calculate the
total dissociative excitation cross section of CoI levels at an exciting electron energy of 100 eV. For the z
2
F°, z
2
G°, and y
2
G° levels, cascade population contributions were also determined. 相似文献
20.
Using the crossed-beam method and a hypocycloidal electron spectrometer, the energy dependence of the ionization cross section for the cadmium atom has been studied in the near-threshold region and the elastic scattering of slow electrons at an angle close to 180° by Cd+ ions was studied for the first time. Within the region under study (0–7 eV above the first atomic ionization potential), a resonance structure determined by the contribution of atomic autoionization states is revealed in both the ionization curve and differential cross section of elastic scattering. The structure in the measured curves has been analyzed with the use of data on the ejected-electron spectra obtained under the excitation of autoionization states of Cd atoms, as well as the data on the optical excitation functions for the atomic spectral lines at λ=430.7 nm (51 P 1-81 S 0), 515.5 nm (51 P 1-71 S 0), 298.0 nm (53 P 2-63 D j ), and 361.0 nm (53 P 2-53 D j ). 相似文献