共查询到20条相似文献,搜索用时 31 毫秒
1.
E. A. Volkova A. M. Popov O. V. Tikhonova 《Journal of Experimental and Theoretical Physics》2002,94(3):525-533
Double ionization is studied by direct numerical integration of the time-dependent Schrödinger equation for a model two-electron system in the field of an electromagnetic wave in the case when the photon energy exceeds the energy required for the removal of both electrons of the atom. The probabilities of single-electron and double ionization are obtained as functions of the radiation intensity. The energy spectra and double pulse distributions of photoelectrons are analyzed. It is shown that single-photon ionization plays a significant role only in the limiting cases of weak and strong fields. The obtained results are used in an analysis of the contributions from different channels to the double-ionization process (in particular, for clarifying the role of the electron-electron interaction). The results of numerical calculations are compared with the analytic model of the phenomenon. 相似文献
2.
E. A. Volkova V. V. Gridchin A. M. Popov O. V. Tikhonova 《Journal of Experimental and Theoretical Physics》2006,102(1):40-52
The ionization of a hydrogen atom in a linearly polarized low-frequency electromagnetic field is investigated by direct numerical integration of the time-dependent Schrödinger equation. The data obtained for various ionization regimes and various initial atomic states are compared with the Keldysh and Perelomov-Popov-Terent’ev (PPT) theories. The validity ranges for the quasi-static model of tunneling ionization and the PPT theory in laser intensity and frequency are determined. The tunneling ionization of the excited 2s and 2p states is discussed. The ionization of a hydrogen atom in an ultrashort (on the order of one optical period) pulse is investigated. 相似文献
3.
V. S. Popov 《Journal of Experimental and Theoretical Physics》2000,91(1):48-66
Calculations are made of the energy and angular distributions of photoelectrons during tunneling ionization of an atom or an ion under the action of high-power laser radiation (for all values of the Keldysh parameter γ). Cases of linear, circular, and elliptic polarizations of the electromagnetic wave are considered. The probability of above-barrier ionization of hydrogen atoms in a low-frequency laser field is calculated. Formulas are given for the momentum spectrum of the electrons when an atomic level is ionized by a general type of alternating electric field (for the case of linear polarization). An analysis is made of tunneling interference in the energy spectrum of the photoelectrons. Analytic approximations are discussed for the asymptotic coefficient C κ of the atomic wave function at infinity (for s-wave electrons). 相似文献
4.
5.
S. V. Borzunov N. L. Manakov A. F. Starace M. V. Frolov 《Journal of Experimental and Theoretical Physics》2011,112(5):725-743
The problem of the shift and broadening of the electron energy levels in the field of two 3D short-range potentials (e.g.,
the model of a negative molecular ion) by a constant electric field F is considered. The interaction of an electron with attraction centers is taken into account in the effective range approximation.
We analyze the cases when both centers maintain weakly bound s states and when the electron state in the field of one of the centers is a p state. Exact numerical results for the shift and the width of the energy levels of a quasi-molecule as functions of field
F, distance R between atomic centers, and the orientation of the quasi-molecule axis relative to vector F are presented, as well as the results of analytic treatment for a number of limiting cases. The exact values of complex energies
of the quasi-molecule are compared with analytic results for a weak field in the case of identical s centers [26], as well as nonequivalent s centers and s-p centers; the applicability boundaries of the weak field approximation are established. It is shown that for large values
of R, the position and width of the levels in a strong field are correctly described in perturbation theory in the exchange interaction.
We analyze the field-induced quasi-intersection of molecular energy levels of the system with nonequivalent atomic centers
and peculiarities in the energy level widths associated with this intersection. The results make it possible to qualitatively
interpret the results of numerical calculations of the probability of homo- and heteronuclear molecules being ionized by a
low-frequency laser field. 相似文献
6.
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
7.
E. A. Volkova A. M. Popov O. V. Tikhonova 《Journal of Experimental and Theoretical Physics》1998,87(5):875-884
The ionization of a simple two-electron model system, viz., the one-dimensional negative hydrogen ion, is investigated using direct numerical integration of the time-dependent Schrödinger equation. The one-and two-electron ionization probabilities as functions of frequency and radiation intensity are obtained. It is shown that two-electron ionization is mediated by both direct and sequential mechanisms. The stabilization of the two-electron system against the ionization process is investigated. The data obtained are compared with calculations performed within the one-dimensional single-particle model of H?. The photoelectron spectrum is analyzed in the region of parameters corresponding to the single-electron ionization regime. 相似文献
8.
Dehua Wang Kaiyun Huang Shenglu Lin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(3):699-706
The ionization of Rydberg hydrogen atoms near a metal surface at different scaled energies above the classical saddle point
energy has been discussed by using the semiclassical method. The results show that the atoms ionize by emitting a train of
electron pulses. In order to reveal the chaotic and escape dynamical properties of this system in detail, the sensitive dependence
of the ionization rate upon the scaled energy is discussed. As the scaled energy is close to the saddle point energy, the
ionization process of the hydrogen atom is nearly the same as the case of hydrogen atom in an electric field. There is only
a single pulse of electrons, with an exponentially decaying tail. With the increase of the scaled energy, the ionization rates
are similar to the case of the hydrogen atom in parallel electric and magnetic field, a series of electron pulses appear in
the ionization process. This is caused by classical chaos, which occurs for the metal surface. Our studies also suggest that
the metal surface can play the role of both the electric and the magnetic fields. Our theoretical analysis will be useful
for guiding experimental studies of the ionization of atoms near the metal surface. 相似文献
9.
E. A. Volkova A. M. Popov O. V. Tikhonova 《Journal of Experimental and Theoretical Physics》2011,113(3):394-406
The dynamics of a model silver atom in the strong radiation field of a Ti:sapphire laser is studied in the Keldysh parameter
regions γ ⩾ 1 and γ ⩽ 1. It is found that in the entire range of Keldysh parameter variations, along with ionization, the
efficient excitation of Rydberg states of the atom with principal quantum numbers n = 6−14 is observed. A Rydberg wavepacket appearing in this case proved stable with respect to ionization; i.e., the atomic
system in strong low-frequency electromagnetic fields becomes stable with respect to ionization. The physical reasons behind
the stabilization are discussed. 相似文献
10.
An investigation of the probability of hydrogen atom ionization by ultra‐short electromagnetic pulses is carried out in the frame of perturbation theory We consider the case when the electric field strength amplitude E0 in a pulse by two orders lower than characteristic atomic field strength Ea (Ea ? 5.1 · 109 V/cm). A detailed investigation of the dependence of the probabilities on the pulse duration was performed for Gaussian pulse shapes. In the case where the carrier frequency of the Gaussian pulse is larger than the atomic ionization potential, the probability goes to the standard limit of perturbation per unit time. At the same pulse durations, the probabilities for carrier frequencies less than the ionization potential go to zero. The frequency dependence of the ionization probability becomes equal to the standard threshold dependence with increasing pulse duration time. A comparison between the ionization effects caused by wavelet pulses without carrier frequency and Gaussian pulses with carrier frequency shows that the same ionization probability values are achieved when the pulse carrier frequency is detuned by about 20% from the ionization threshold. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
11.
12.
V. S. Popov B. M. Karnakov V. D. Mur 《Journal of Experimental and Theoretical Physics》1999,88(5):902-912
Lorentz ionization emerges due to the motion of atoms or ions in a strong magnetic field. We use the semiclassical approximation
to calculate the probability w
L
of Lorentz ionization. We also find the stabilization factor S, which takes into account the reduction by the magnetic field of the probability of ionization decay of the bound s state. We estimate the probabilities w
L
in magnetic-cumulation experiments and in astrophysics. We also qualitatively examine the dynamics of the magnetic cumulation
process with allowance for the conductivity of the shell. Finally, we discuss a paradox related to the use of the quasistationary
solution at the shell expansion stage.
Zh. éksp. Teor. Fiz. 115, 1642–1663 (May 1999) 相似文献
13.
A. V. Kudrin L. E. Kurina G. A. Markov 《Journal of Experimental and Theoretical Physics》1997,85(4):697-704
An investigation is made of the self-interaction of whistler waves (whistlers) involving the formation of waveguide channels
in a collisional magnetoactive plasma as a result of its additional ionization by the field of the propagating wave. Simplified
equations are derived to describe the behavior of the whistler field in a channel of enhanced plasma density in the presence
of electron collisions. Self-consistent distributions of the field and the plasma corresponding to steady-state ionization
self-channeling of whistlers are obtained by numerically solving the equations for the field together with balance equations
for the electron density and energy. Our estimates indicate that this effect can be observed under laboratory conditions.
Zh. éksp. Teor. Fiz. 112, 1285–1298 (October 1997) 相似文献
14.
Summary We report on calculations of differential and total ionization cross-sections of hydrogen atoms irradiated by two radiation
fields with different properties. One of the fields is of low intensity and relatively high frequency, the other is of low
frequency and high intensity. In particular, we show that the inclusion of the multimode structure of the low-frequency laser
field modifies considerably the shape of the angular distribution of the photoelectrons and the rates of ionization into the
different channels characterized by the number of low-frequency photons exchanged. Further, we find that the average energy
exchanged between the photoelectrons and the low-frequency radiation field is independent of the statistical properties of
the low-frequency laser field. 相似文献
15.
The dynamics of a hydrogen atom and a 3D model quantum system with a short-range potential is investigated using the direct numerical integration of the nonstationary Schrödinger equation in a wide range of laser intensities and frequencies. The simulation data are compared with the predictions of variants of the Keldysh-type theories. It is demonstrated that, in the low-frequency (tunnel) limit, the ionization rates of the systems with the Coulomb and short-range potentials and the same values of the ionization potential significantly differ from each other whereas, in the high-frequency (single-photon) limit, we do not observe a substantial difference between the ionization rates. Specific features of the angular distribution of the photoelectron emission and the photoelectron energy spectra are investigated in detail. In addition, the ionization suppression is studied for both Coulomb- and short-range-potential atoms. The stabilization is due to the dramatic reconstruction of the atom in the presence of a strong laser field and the formation of a new system (Kramers-Henneberger atom) that exhibits an increasing resistance to the ionization upon an increase in the laser intensity. In the two-photon ionization regime, the stabilization phenomenon is substantially more pronounced for the system with the Coulomb potential. This results from the effective excitation of the Rydberg states of the dressed atom in the strong-field limit. 相似文献
16.
V. P. Silin 《Journal of Experimental and Theoretical Physics》1997,84(2):262-271
Transport equations are obtained in the nine-moment approximation for plasmas in intense radiation fields where the amplitude
of the electron oscillations in the electromagnetic field exceeds the thermal speed. It is shown that for plasmas with a high
degree of ionization, Z, the electron thermal conductivity is higher by approximately a factor of Z. The change in the frictional force on electrons colliding with ions owing to the effect of the radiation field leads to
the possibility of electron acceleration and to a change in the sign of the dc and low-frequency electrical conductivities.
Zh. éksp. Teor. Fiz. 111, 478–495 (February 1997) 相似文献
17.
O. Budriga V. Florescu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):205-210
We study Compton scattering on the ground state of the hydrogen atom in the presence of an intense low-frequency electric
field (the laser) of arbitrary polarization, for incident and scattered photons of energies around 15 keV. The adopted formalism
is the nonrelativistic one developed by Voitkiv et al. [J. Phys. B: At. Mol. Opt. Phys. 36, 1907 (2003)] and applied by them for a circularly polarized laser. We explore the spectrum and the electron energy distribution
in their dependence on the incident photon energy or electric field intensity, for different polarizations. 相似文献
18.
V. S. Popov B. M. Karnakov V. D. Mur 《Journal of Experimental and Theoretical Physics》1998,86(5):860-874
A semiclassical theory is developed for the ionization of atoms and negative ions in constant, uniform electric and magnetic
fields, including the Coulomb interaction between the electron and the atomic core during tunneling. The case of crossed fields
(Lorentz ionization) is examined specially, as well as the limit of a strong magnetic field. Analytic equations are derived
for arbitrary fields ℰ and ℋ that are weak compared to the characteristic intraatomic fields. The major results of this paper
are obtained using the “imaginary time” method (ITM), in which tunneling is described using the classical equations of motion
but with purely imaginary “time.” The possibility of generalizing the ITM to the relativistic case, as well as to states with
nonzero angular momentum, is pointed out.
Zh. éksp. Teor. Fiz. 113, 1579–1605 (May 1998) 相似文献
19.
The mechanism for dense-gas ionization is analyzed in the case when the deceleration of electrons by gas can be neglected in the equation of motion of a single electron. An expression for the electron energy distribution function in the presence of a strong field is derived. The characteristic width of the distribution corresponds to the energy acquired by the electron at a length determined by the inverse Townsend coefficient. The electron energy distributions are calculated for various distances form the cathode. It is demonstrated that the distribution becomes independent of the coordinate at a distance from the cathode that is significantly greater than the inverse Townsend coefficient. In this case, the distribution coincides with the distribution obtained with analytical calculations. The absence of the coordinate dependence is realized even in the presence of an extremely strong field when, in accordance with the commonly accepted point of view, the majority of electrons are runaway electrons. 相似文献
20.
We develop a new model of a Thomas-Fermi cluster that describes the distribution of electrons in alkaline clusters with many
atoms. We examine the classical multiple ionization of such a cluster by a strong electromagnetic field. Finally, we calculate
the degree of ionization as a function of the field strength.
Zh. éksp. Teor. Fiz. 115, 2014–2019 (June 1999) 相似文献