共查询到20条相似文献,搜索用时 31 毫秒
1.
I. Yu. Yurova N. K. Shevyakina 《Russian Journal of Physical Chemistry B, Focus on Physics》2014,8(1):1-8
An analytical expression for the amplitude of ionization of the hydrogen molecule by electron impact in the first Born approximation with a one-center Coulomb continuum wave function is derived. The case where the incident electron energy is much greater than the ejected electron energy is considered. The molecular wave functions were constructed in the approximation of linear combination of atomic orbitals with overlapping configurations. The role of the orthogonalization of the initial and final wave functions of the active electron of the target is elucidated. The triple differential ionization cross sections for the different orientations of the molecular axis and that averaged over all orientations are calculated. The secondary electron angular distribution is represented in the form of three-dimensional images. A comparison with the results of other theoretical calculations and experimental data is performed. 相似文献
2.
The total cross sections of He and He+ ionization by an electron impact are calculated in the first Born approximation. Calculations of the matrix elements are carried out by the Fock-Dirac multiconfiguration relativistic method using an intermediate type of coupling with orthogonal functions of the initial and final states. A single-electron wave function of the continuous spectrum for an Auger electron is obtained using the Fock-Dirac single-configuration method. The results of the calculations performed with orthogonal and nonorthogonal wave functions of the initial and final states are compared. The ionization cross sections are calculated for cases in which a knock-on electron of the continuous spectrum is described by both the orthogonal and nonorthogonal wave functions with respect to the wave functions of the core electrons. 相似文献
3.
O. B. Prepelitsa 《Journal of Experimental and Theoretical Physics》1999,89(3):428-434
This paper examines the multiphoton ionization of the ground state of the hydrogen atom in the field of a circularly polarized
intense electromagnetic wave. To describe the states of photoelectrons, quasiclassical wave functions are introduced that
partially allow for the effect of an intense electromagnetic wave and that of the Coulomb potential. Expressions are derived
for the angular and energy distributions of photoelectrons with energies much lower than the ionization potential of an unperturbed
atom. It is found that, due to allowance for the Coulomb potential in the wave function of the final electron states, the
transition probability near the ionization threshold tends to a finite value. In addition, the well-known selection rules
for multiphoton transitions in a circularly polarized electromagnetic field are derived in a natural way. Finally, the results
are compared with those obtained in the Keldysh-Faisal-Reiss approximation.
Zh. éksp. Teor. Fiz. 116, 807–820 (September 1999) 相似文献
4.
S.?Borbély K.?T?kési L.?Nagy 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,59(3):337-348
The ionization of the water molecule by intense ultrashort half-cycle electric pulses is studied theoretically. The formation
of the electron wave packets in the continuum was investigated by calculating ionization probability densities using classical
and quantum mechanical models. Single active electron and frozen core calculations were performed within the hydrogenic approximation.
Electrons from the highest occupied molecular orbital 1b11b_1 were considered. We found good agreement between the classical and quantum mechanical calculation at high intensities, where
the over-the-barrier ionization mechanism is dominant. 相似文献
5.
In this communication we present theoretical demonstration of electron dichroism in the relativistic (e, 2e) process for K-shell ionization of atoms in non-coplanar asymmetric geometry. The theoretical formalism has been developed
in plane wave Born approximation and in this approximation the triple differential cross-section (TDCS) has been expressed
as a product of kinematical factors and atomic structure functions. The longitudinal spin asymmetry in the relativistic (e, 2e) process on K-shell of atoms has been shown to depend on the interference between the transition charge and component of
the transition current in the direction perpendicular to the scattering plane. Further, the longitudinal spin asymmetry has
been shown to depend on incident electron energy, atomic number of the target, azimuthal angle of the ejected electron and
scattered electron angle. 相似文献
6.
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
7.
Simultaneous ionization and excitation of helium by electron impact is considered in an improved second Born approximation.
The wave function of the low energy ejected electron is obtained in the field of residual He+ ion in 2s-state. The calculation has been done for the processe
−+He→e
−+He+(2s)+e
− in the coplanar asymmetric geometry with Hartree-Fock wave function of Byron and Joachain for the helium ground state and
the results are compared with the absolute experimental data of Dupreet al [J. Phys.
B25, 259 (1992)] at ∼ 5.5 keV incident energy. Our results are found to increase the ratio of the recoil peak to binary peak
intensity by about 30% over the first Born results and thus to bring it closer to the experimental data. 相似文献
8.
K. B. Korotchenko 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2010,4(4):599-602
A new type of combinational channeling radiation induced by subbarrier (interband) transitions for the transverse motion of
relativistic electrons (positrons) is studied. It is known as diffracted channeling radiation (DCR). The formula describing
the DCR angular distribution in the case of axial channeling is obtained by taking into account the band structure of energy
levels for the transverse motion of electrons (positrons). It is shown that, in the two-wave approximation of the wave function
A(r) of virtual photons, the DCR matrix elements in the dipole approximation for axial and plane channeling coincide formally
(with the dimension of the problem taken into account). However, the formulas for DCR angular distributions in the cases of
axial and plane channeling differ considerably. 相似文献
9.
The angular distribution of the five-fold differential cross section for the electron impact double ionization of He (21
S) and He (23
S) has been studied. The kinematical conditions for maxima/minima in the angular distribution for the two cases have been compared.
The two-step process for the double ionization is found to contribute very little in the triplet case. 相似文献
10.
A simple jellium model is constructed in order to obtain one-electron wave functions for the valence electrons of the fullerene. With this jellium wave function we have calculated ionization cross sections for proton-C60 + collisions in the semiclassical approximation. For higher projectile velocities, for which the semiclassical approximation is valid also for electron impact, theoretical cross sections fit satisfactorily the experimental data of Völpel et al. [Phys. Rev. Lett. 71 (1993) 3439]. 相似文献
11.
The effect of wave function orthogonality on the simultaneous ionization and excitation of helium 下载免费PDF全文
Within the framework of the first-order Born approximation, the triple differential cross sections (TDCSs) for simultaneous ionization and excitation of helium are calculated. The wave function of the ejected electron is chosen to be orthogonal or non-orthogonal to the wave function of the bound electron before ionization. It is found that the orthogonality has a strong effect on the TDCS, especially when plane waves and Coulomb waves are used to describe the projectile and the ejected electron. 相似文献
12.
The impact of the strongly attractive electromagnetic field of heavy nuclei on electrons in quasi-elastic (e, e') scattering is often accounted for by the effective momentum approximation. This method is a plane wave Born approximation
which takes the twofold effect of the attractive nucleus on initial- and final-state electrons into account, namely the modification
of the electron momentum in the vicinity of the nucleus, and the focusing of electrons towards the nuclear region leading
to an enhancement of the corresponding wave function amplitudes. The focusing effect due to the attractive Coulomb field of
a homogeneously charged sphere on a classical ensemble of charged particles incident on the field is calculated in the highly
relativistic limit and compared to results obtained from exact solutions of the Dirac equation. The result is relevant for
the theoretical foundation of the effective momentum approximation and describes the high-energy behavior of the amplitude
of continuum Dirac waves in the potential of a homogeneously charged sphere. Our findings indicate that the effective momentum
approximation is a useful approximation for the calculation of Coulomb corrections in (e, e') scattering off heavy nuclei for sufficiently high electron energies and momentum transfer. 相似文献
13.
A. Yu. Elizarov 《Journal of Experimental and Theoretical Physics》1998,86(3):455-458
An experimental and theoretical study is performed of the angular photoelectron distribution for three-photon ionization of
Ba atoms through the 2ω-excited intermediate state 6p
2(1
S
0) and the auto-ionized state 6p8s(3
P
1). Rotation of the polarization plane of dye-laser radiation allowed us to investigate the photoelectron angular distribution.
Electrons were counted with the help of a time-of-flight electron spectrometer. The density-matrix formalism is used to obtain
expressions for the angular dependence of the differential ionization probability. Possible experiments are discussed.
Zh. éksp. Teor. Fiz. 113, 834–840 (March 1998) 相似文献
14.
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
15.
Avi Marchewka Er’el Granot 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2014,68(9):1-7
The photo-absorption cross sections for the dissociative ionization and dissociative excitation of H 2 + are calculated for photon polarization parallel and perpendicular to the internuclear axis. The wavefunctions for the initial and final states are prepared using the Born-Oppenheimer approximation. For dissociative ionization, the cross section and angular distribution of photo-electrons are compared with those calculated with the fixed-nuclei approximation. For dissociative excitation, the cross sections for H?(N = 1~4) productions are shown. 相似文献
16.
S.M. Younger 《Journal of Quantitative Spectroscopy & Radiative Transfer》1982,27(5):541-544
Electron impact ionization cross sections for the ions Fe(XVII)-(XXVI) have been computed in a distorted wave exchange approximation. Analytic fits are provided for the cross section data, as well as for the rate coefficients assuming a Maxwellian electron velocity distribution. For ejection of a 2p ground state electron, the scaled ionization rate was found to depend linearly on the number of 2p electrons in the ion. 相似文献
17.
The cross sections of the photoionization and the electron impact-induced ionization of Yb atoms from the excited 6s6p(3
P
1) state are numerically calculated. Matrix elements are computed in multielectron relativistic and nonrelativistic approximations
with allowance for the superposition of configurations and a relaxation effect. The radial part of the electron wavefunction
in a continuous spectrum is calculated using the solutions to one-configuration Hartree-Fock and Dirac-Fock equations. The
cross sections calculated by a relativistic method are compared to those for a nonrelativistic approximation. The ratios of
the radiation reduced matrix elements and the phase shifts of the wavefunctions of a continuous spectrum calculated for the
6p ɛs and 6p → ɛd transitions are compared to the values obtained by approximating the experimental dependences of the angular distribution
of photoelectrons for the photoionization by ultraviolet radiation from an oriented excited state. 相似文献
18.
P. Mandelbaum J. L. Schwob 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,49(2):173-184
Detailed level-by-level calculations of cross sections and rate coefficients for electron impact direct and indirect ionization
of ions belonging to the GaI isoelectronic sequence (ground 3d
104s
24p) have been performed. The cross sections are presented in the energy range near the threshold for the five ions Kr5+, Mo11+, Xe23+, Pr28+ and Dy35+. The rate coefficients are given for ions from Kr5+ to U61+ in the GaI sequence at seven electron temperatures (kT
e = 0.1E
I
, 0.3E
I
, 0.5E
I
, 0.7E
I
,E
I
, 2E
I
and 10E
I
, where E
I
is the first ionization energy). The calculations include the contribution of direct ionization (DI) calculated using the Lotz formula approximation and the contributions of excitation-autoionization (EA) computed in the
framework of the distorted wave (DW) approximation for the 4s-nl, 3d-nl and 3p-nl resonant inner-shell excitations. The ionization enhancement due to the EA channels is presented as a function of Z along
the GaI isoelectronic sequence. The present results show the great importance of the EA processes; an ionization enhancement factor of up to 10 is predicted for instance for La26+ (Z = 57) at electron temperature of coronal equilibrium maximum abundance. 相似文献
19.
The interference structure of the angular distributions in the high-energy part of the above-threshold ionization spectrum
is calculated. The components of the wave packet of the ionized electron that interfere with one another during the interaction
with the parent ion are identified. It is shown that the angular distribution averaged over the interference oscillations
is determined mainly by the angular dependence of the effective interaction time.
Pis'ma Zh. éksp. Teor. Fiz. 68, No. 12, 858–863 (25 December 1998) 相似文献
20.
Differential cross sections and angular distributions of protons from the 2H(e, p)e′n reaction have been measured at four incident electron energies. The proton angular distributions were measured with the neutron-proton relative energy approximately constant, and an 85° differential cross section was measured as a function of the incident electron energy. The electrodisintegration cross section was calculated using the Hulthén wave function for the ground state with a plane wave for the final state. Reasonable agreement between experiment and theory is found. 相似文献