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1.
The influence of the Stark effect on multiphoton ionization of Ba atoms under conditions when the dynamic polarizability depends
strongly on the frequency of the laser radiation is investigated. It is found that for some electric field strengths ε of the laser radiation this effect gives rise to resonance peaks in the Ba+ ion yield as a function of the laser radiation frequency at frequencies corresponding to single-photon transitions between
the excited states. These frequencies can differ substantially from the frequencies corresponding to the conventional multiphoton
excitation of these states from the ground states of the atoms. Peaks in the ion yield as a function of ε behave differently from the conventional Stark effect—their position on the frequency scale does not depend strongly on ε. The conditions under which such an induced resonance structure appears are determined.
Zh. éksp. Teor. Fiz. 113, 499–512 (February 1998) 相似文献
2.
A.?V.?Akimov E.?O.?Tereshchenko S.?A.?Snigirev A.?Yu.?Samokotin A.?V.?Sokolov N.?N.?Kolachevski? V.?N.?Sorokin 《Journal of Experimental and Theoretical Physics》2009,109(3):359-369
The resonant interaction of 87Rb atoms in a magneto-optical trap with femtosecond laser radiation in the spectral range 760–820 nm has been investigated
experimentally. It has been demonstrated that femtosecond laser radiation with a spectral width of 10 nm interacts with an
atomic ensemble as a set of spectrally narrow modes and as an ionizing laser field simultaneously. The dynamics of trap loading
in the presence of ionization by femtosecond radiation has been studied, and the 5D
5/2 level population produced by an additional weak laser field has been measured. 相似文献
3.
B. A. Zon 《Journal of Experimental and Theoretical Physics》1997,85(1):61-67
The theory of tunneling ionization of atoms is generalized to ionization of symmetric top molecules, either polar or nonpolar.
Low-lying excited states of molecules, for which the ordinary Born-Oppenheimer approximation holds, and high-lying excited
states, for which the inverse Born-Oppenheimer approximation holds, are discussed. Ionization in a constant external field
is analyzed, as is ionization in an alternating field. It is shown that the orientation of the molecule’s axis along the field
does not lead to any appreciable increase in the ionization probability as compared to other orientations.
Zh. éksp. Teor. Fiz. 112, 115–127 (July 1997) 相似文献
4.
采用三维粒子动力学模拟方法研究了甲烷团簇在超短强激光脉冲激励下的爆炸动力学行为,重点讨论了几种典型的内电离机理对团簇爆炸过程中离子的价态和动能的影响.研究表明,在激光脉冲强度比较小的情况下,团簇中的原子主要是在光场作用下通过隧道电离的方式发生电离.当激光场进一步增强时,势垒压低电离是电离的主要方式.在相同的较高激光强度下,团簇更容易通过势垒压低电离达到高的电离价态.团簇发生电离后,其内部库仑电场的点火电离效应和内部滞留自由电子的碰撞电离效应也将增强团簇的再次电离过程.
关键词:
超短强激光脉冲
甲烷团簇
内电离 相似文献
5.
The resonance structure of doubly-charged-ion production during the ionization of Ba atoms by infrared radiation (color-center
laser radiation) is identified. It is shown that this structure is due to the excitation of states of the neutral Ba atom
which are strongly perturbed as a result of the Stark effect under conditions such that the dynamic polarizability has large
absolute values and depends strongly on the frequency of the radiation.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 11, 796–800 (10 December 1998) 相似文献
6.
A theory of coherent interaction between a sequence of ultrashort laser pulses and planar, thin-film microcavities in the
form of Fabry-Perot resonators containing resonating atoms has been developed. The dynamics of transmission of single laser
pulses has been analyzed numerically. Analytic solutions of the problem of four-wave mixing of optical fields separated in
time have been obtained in the small-area approximation. The dynamic efficiency of conversion of incident waves to the coherent
response field (photon echo) generated in a microcavity can be higher than in the case of a bulk resonant structure. Specific
features of photon echo generation in a microcavity for arbitrary “areas” of laser pump pulses are discussed.
Zh. éksp. Teor. Fiz. 114, 1578–1594 (November 1998) 相似文献
7.
K. Blaum B.A. Bushaw S. Diel Ch. Geppert A. Kuschnick P. Müller W. Nörtershäuser A. Schmitt K. Wendt 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(1):37-44
High-resolution resonance ionization mass spectrometry has been used to measure isotope shifts and hyperfine structure in
all (J
= 2-6) and the transitions of gadolinium (Gd I). Gadolinium atoms in an atomic beam were excited with a tunable single-frequency laser in
the wavelength range of 422-429 nm. Resonant excitation was followed by photoionization with the 363.8 nm line of an argon
ion laser and resulting ions were mass separated and detected with a quadrupole mass spectrometer. Isotope shifts for all
stable gadolinium isotopes in these transitions have been measured for the first time. Additionally, the hyperfine structure
constants of the upper states have been derived for the isotopes
155, 157
Gd and are compared with previous work. Using prior experimental values for the mean nuclear charge radii, derived from the
combination of muonic atoms and electron scattering data, field shift and specific mass shift coefficients for the investigated
transitions have been determined and nuclear charge parameters for the minor isotopes
152, 154
Gd have been calculated.
Received 18 November 1999 相似文献
8.
G. P. Miroshnichenko 《Journal of Experimental and Theoretical Physics》2009,109(2):193-206
A theory of the discrete photodetection of quantum jumps on the V configuration of atomic levels has been developed. A three-level
source atom is placed in a cavity excited by a resonance fluorescence field. The cavity is tuned to exact resonance with an
atomic transition. The cavity mode state is tested by a flux of unexcited (at the entrance) probe atoms passing through the
cavity. The energy states of the outgoing probe atoms are detected by ionization chambers, which are assumed ideal. This a
posteriori statistical information is indirectly related to the numerical characteristics of a measured quantum system consisting
of the source atom and cavity mode. The “tuning” conditions for a discrete photodetector, i.e., the rules for choosing the
parameters and durations of the interactions of the cavity mode with the probe and source atoms, intensities of the pump and
probe fields that are necessary for observing quantum jumps from the “bright” state to the “dark” one and vice versa, have
been determined. A two-state model that describes the dynamics of a quantum jump has been analyzed. The formulas have been
obtained for the observable characteristics of quantum jumps: the mean residence time of the quantum system in quasistationary
states (durations of the bright and dark periods), probabilities of quantum jumps, mean excitation levels of the quantized
cavity mode, etc. 相似文献
9.
A. V. Andreev S. Yu. Stremoukhov O. A. Shutova 《Journal of Experimental and Theoretical Physics》2010,111(6):936-948
Specific features of ionization of single atoms by laser fields of a near-atomic strength are investigated. Calculations are
performed for silver atoms interacting with femtosecond laser pulses with wavelengths λ = 800 nm (Ti:Sapphire) and λ = 1.064
μm (Nd:YAG). The dependences of the probability of ionization and of the form of the photoelectron energy spectra on the field
of laser pulses for various values of their duration are considered. It is shown that the behavior of the probability of ionization
in the range of subatomic laser pulse fields is in good agreement with the Keldysh formula. However, when the field strength
attains values close to the atomic field strength, the discrepancies in these dependences manifested in a decrease in the
ionization rate (ionization stabilization effect) or in its increase (accelerated ionization) are observed. These discrepancies
are associated with the dependence of the population dynamics of excited discrete energy levels of the atom on the laser pulse
field amplitude. 相似文献
10.
V.S. Letokhov 《Physics letters. A》1975,51(4):231-232
A modification of field ion microscope, based on radical reduction of intensity of electric field essential for field-ionization of imaging gas atoms, is suggested. For this purpose the imaging gas atoms are excited by a laser radiation to quantum states nearby the ionization limit. As excited atoms approach the point the field ionization must occur in rather weak fields (~107 V/cm) which eliminate electric field induced effects of molecular evaporation and decomposition. 相似文献
11.
We study the Ulam problem for long times (several million collisions) by numerical methods. We show that in the diffusion
regime, which is valid for moderate times, this problem is mathematically equivalent to the problem of the diffusive ionization
of atomic Rydberg states by microwave radiation. It is concluded that the diffusion regime sets in only for a very small number
of initial conditions (field phases). It is theorized that the analogy between the two problems can be extrapolated to times
longer than the diffusion time. We show in the Ulam problem that after the diffusional buildup of energy has finished, the
quasistationary regime does not continue indefinitely: after several million particle-wall collisions the energy rapidly drops
to zero. On the basis of this extrapolation we examine the possibility that an electron which has reached the continuous spectrum
will not fly off to infinity (ionization), but will return to bound Rydberg states of the atoms (if the field acts for a sufficiently
long time). This can make the diffusive ionization probability much lower than the value given by the known estimates.
Zh. éksp. Teor. Fiz. 114, 37–45 (July 1998) 相似文献
12.
O. V. Ovodova A. M. Popov O. V. Tikhonova 《Journal of Experimental and Theoretical Physics》1997,85(2):257-263
A one-dimensional model of a helium atom in an intense field of a femtosecond electromagnetic pulse has been constructed using
the Hartree technique. “Exact” calculations have been compared to the approximations of “frozen” and “passive” electrons.
A nonmonotonic dependence of the single-electron ionization probability on the radiation intensity has been detected. Minima
in the ionization probability are due to multiphoton resonances between different atomic states due to the dynamic Stark effect.
We suggest that the ionization suppression is due to the interference stabilization in this case.
Zh. éksp. Teor. Fiz. 112, 470–482 (August 1997) 相似文献
13.
Quantum beats between the fine structure levels of highly excitedn 2 D levels of sodium atoms have been measured by investigating the field electrons. The states were populated by stepwise excitation with two dye lasers and an electric field pulse was applied a certain time after the laser excitation. The quantum beat signal is observed when the time delay between excitation and ionization is varied. The fine structure splitting forn=21 to 31 has been measured. 相似文献
14.
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
15.
B. A. Zon 《Journal of Experimental and Theoretical Physics》1999,89(2):219-222
A formula for describing the N-electron ionization of atoms by a dc field and laser radiation in the tunneling regime is derived theoretically, and numerical
examples for noble-gas atoms are presented.
Zh. éksp. Teor. Fiz. 116, 410–417 (August 1999) 相似文献
16.
E. A. Yakshina D. B. Tretyakov V. M. Entin I. I. Beterov I. I. Ryabtsev 《Journal of Experimental and Theoretical Physics》2020,130(2):170-182
The dipole blockade effect at laser excitation of mesoscopic ensembles of Rydberg atoms lies in the fact that the excitation of one atom to a Rydberg state blocks the excitation of other atoms due to the shift in the collective energy levels of interacting Rydberg atoms. It is used to obtain the entangled qubit states based on single neutral atoms in optical traps. In this paper, we present our experimental results on the observation of the dipole blockade for mesoscopic ensembles of 1–5 atoms when they are detected by the selective field ionization method. We have investigated the spectra of the three-photon laser excitation 5S1/2 → 5P3/2 → 6S1/2 → nP3/2 of cold Rydberg Rb atoms in a magneto-optical trap. We have found that for mesoscopic ensembles this method allows only a partial dipole blockage to be observed. This is most likely related to the presence of parasitic electric fields reducing the interaction energy of Rydberg atoms, the decrease in the probability of detecting high states, and the strong angular dependence of the interaction energy of Rydberg atoms in a single interaction volume. 相似文献
17.
A new technique is described which allows Doppler-free, isotope-selective excitation of atoms by continuous wave laser radiation and continuous ionization of the atoms by an electric field. The atoms are excited to high Rydberg states in an electric-field-free region of a collimated atomic beam. Because the lifetimes of Rydberg atoms are long they can reach a spatially separated region of the atomic beam where they are ionized by a continuous electric field with a probability of unity. In the case of lithium we obtained a 103 times larger ion signal by field ionization of Rydberg atoms than by direct photoionization from low excited states. 相似文献
18.
The high-resolution three-dimensional photoelectron momentum distributions via above-threshold ionization(ATI)of Xe atoms are measured in an intense near circularly polarized laser field using velocity map imaging and tomography reconstruction. Compared to the linearly polarized laser field, the employed near circularly polarized laser field imposes a more strict selection rule for the transition via resonant excitation, and therefore we can selectively enhance the resonant ATI through certain atomic Rydberg states. Our results show the self-reference ionization delay, which is determined from the difference between the measured streaking angles for nonadiabatic ATI via the 4 f and 5 f Rydberg states, is 45.6 as. Our method provides an accessible route to highlight the role of resonant transition between selected states, which will pave the way for fully understanding the ionization dynamics toward manipulating electron motion as well as reaction in an ultrafast time scale. 相似文献
19.
Single colour three photon resonant ionization (2 + 1) is observed in atomic potassium vapour in a heat pipe oven using an
excimer laser pumped dye laser. Using wavelengths between 570 nm and 603 nm various2S and2D Rydberg states are populated by two photon excitation. Third photon of the same wavelength ionizes the atoms. Rydberg states
up ton ⋍ 50 are observed. Electric field as low as 1 V/cm causes extensive Stark mixing of the states. This results in progressively
higher three photon ionization signals via the perturbed2P and2F Rydberg states. The three photon ionization process is studied using both linearly and circularly polarized incident light.
The experiment shows qualitatively that the2P Rydberg states are perturbed primarily by the2D states in the prescence of an external electric field and to a much smaller extent by2S states. This is also explained theoretically by calculating the Stark mixing coefficients under the Bates and Daamgard (1949)
approximation. Implication for a similar effect in other alkali elements is discussed. 相似文献
20.
The paper presents a brief review of the scientific work performed by the authors in the field of quantum mechanics and atomic, laser, and mathematical physics. The following problems are considered: the semiclassical theory of tunneling and multiphoton ionization of atoms and ions in a strong electromagnetic field; generalization of the Keldysh ionization theory to the relativistic case; calculation of the Coulomb corrections to the ionization rate of atoms for arbitrary values of the adiabaticity parameter γ: from γ ≪ 1 (the adiabatic region) to γ ≫ 1, when the laser field changes its direction and magnitude many times during the time of flight of the electron through the barrier; the Lorentz ionization of atoms moving in a constant magnetic field; the WKB approximation and the imaginary time method for describing electron tunneling through a time-varying barrier; the Stark effect in a strong field; the energy spectrum of a hydrogen atom in a strong and superstrong magnetic field; quantization with account of the barrier transparency; creation of electron-positron pairs from vacuum in a constant electric or intense pulsed (laser) field and the dependence of the number of pairs on the intensity and frequency of the laser field; the Feynman method of disentanglement of noncommuting operators and its applications: transitions between atomic states in an alternating magnetic field (the Majorana problem); a quantum oscillator with time-dependent frequency; and a singular oscillator. The mathematical problems of quantum mechanics are considered: the fall of a particle to the center; modification of the Bohr-Sommerfeld quantization condition for potentials with a barrier and the Kramers matching conditions; divergence of perturbation series and their summation; eigenvalues of the Casimir operators for irreducible representations of Lie groups, including the SU(2), SU(3), and SU(6) groups, which are widely used in physics. 相似文献