共查询到20条相似文献,搜索用时 31 毫秒
1.
A. D. Gazazyan 《Journal of Experimental and Theoretical Physics》1998,86(4):650-656
This paper studies the effect of a transition into the continuous spectrum on the “collapse” and “revival” of population oscillations
in an atom. It is shown that at large values of the mean number of photons in a radiation field and in conditions of weak
ionization the phenomena of collapse and revival can still be observed, but the amplitude of population oscillations decreases
exponentially because of the damping of the level. The interaction of a quantized electromagnetic field with a Λ system of
an atom when one state is continuous is examined. Expressions are derived for the probability of “survival” of the atom when
the quantized field was initially in a state with a given number of photons and when it was in a coherent state. An approximate
calculation of the sum in averaging over the photon number distribution in the case of a coherent field leads to expressions
for the probabilities of survival of the atom that transform into expressions, as the mean number of photons tends to infinity,
corresponding to the case of a field in the representation of a fixed number of photons. The possibility of a stable state
existing in a coherent quantized field is examined. It is found that for a Λ system the condition for the existence of a stable
state remains valid in the case of a coherent state of the field when the photon number is large.
Zh. éksp. Teor. Fiz. 113, 1193–1205 (April 1998) 相似文献
2.
Stability of a Model of Relativistic Quantum Electrodynamics 总被引:1,自引:0,他引:1
The relativistic “no pair” model of quantum electrodynamics uses the Dirac operator, D(A) for the electron dynamics together with the usual self-energy of the quantized ultraviolet cutoff electromagnetic field
A– in the Coulomb gauge. There are no positrons because the electron wave functions are constrained to lie in the positive
spectral subspace of some Dirac operator, D, but the model is defined for any number, N, of electrons, and hence describes a true many-body system. In addition to the electrons there are a number, K, of fixed nuclei with charges ≤Z. If the fields are not quantized but are classical, it was shown earlier that such a model is always unstable (the ground
state energy E=−∞) if one uses the customary D(0) to define the electron space, but is stable (E > − const.(N+K)) if one uses D(A) itself (provided the fine structure constant α and Z are not too large). This result is extended to quantized fields here, and stability is proved for α= 1/137 and Z≤ 42. This formulation of QED is somewhat unusual because it means that the electron Hilbert space is inextricably linked
to the photon Fock space. But such a linkage appears to better describe the real world of photons and electrons.
Received: 8 September 2001 / Accepted: 18 March 2002 相似文献
3.
V. N. Lazukov P. A. Alekseev E. S. Klement’ev I. P. Sadikov N. B. Kol’chugina O. D. Chistyakov 《Journal of Experimental and Theoretical Physics》1999,88(6):1202-1207
We have studied the evolution of the inelastic neutron magnetic scattering spectra of a compound with cubic symmetry, CeInCu2, in the temperature range 10–130 K, and also their transformation with variation of the Kondo temperature T
K
due to substitution of cerium ions in the system Ce1−x
(La,Y)xInCu2 at T=10 K. It turns out that the energy of the transition between the ground state and excited state of the 4 f electrons (ΔCF) in the crystal electric field in CeInCu2 increases with growth of the population of the ground state as the temperature is reduced, with a slight change in its intensity.
Such behavior is inconsistent with the notion of classical one-ion effects of the crystal electric field. We have found that
the scale of the observed variations in the excitation spectra of the 4f electrons depends on the Kondo temperature T
K
and is insensitive to disorder in the rare-earth sublattice. Thus, despite the fact that T
K
≪ΔCF, hybridization with states in the conduction band has a substantial effect on all parameters of the excitation spectrum of
the ground multiplet of the 4f electrons at low temperatures.
Zh. éksp. Teor. Fiz. 115, 2197–2206 (June 1999)
A. A. Baikov Institute of Metallurgy 相似文献
4.
We consider a large atom with nuclear charge Z described by non-relativistic quantum mechanics with classical or quantized electromagnetic field. We prove that the absolute
ground state energy, allowing for minimizing over all possible self-generated electromagnetic fields, is given by the non-magnetic
Thomas-Fermi theory to leading order in the simultaneous Z → ∞, α → 0 limit if Z
α
2 ≤ κ for some universal κ, where α is the fine structure constant. 相似文献
5.
Charles Fefferman Jürg Fröhlich Gian Michele Graf 《Communications in Mathematical Physics》1997,190(2):309-330
We prove that the quantum-mechanical ground state energy of a system consisting of an arbitrary number, M, of static nuclei of atomic number ≤Z and of an arbitrary number, N, of Pauli electrons interacting with the quantized, ultraviolet-cutoff radiation field is bounded below by $-K.M, where K is a finite constant depending on Z, on the finestructure constant α and on the ultraviolet cutoff Λ, with , as , and K' independent of Λ.
Received: 4 September 1996/ Accepted: 9 April 1997 相似文献
6.
M. Z. Smirnov 《Journal of Experimental and Theoretical Physics》1997,85(3):441-446
An open quantum system, which consists of a “dressed” two-level atom, i.e., an atom interacting with a classical multifrequency
field, and a single quantized mode of an electromagnetic field, is examined. It is shown that when the frequency of the quantized
mode coincides with one of the transition frequencies between the quasienergy levels, two interaction mechanisms, which differ
in the dynamics of the populations of the quasienergy states, can be realized.
Zh. éksp. Teor. Fiz. 112, 818–827 (September 1997) 相似文献
7.
G. K. Ivanov G. V. Golubkov S. V. Drygin I. E. Cherlina 《Journal of Experimental and Theoretical Physics》1997,84(5):888-892
Ionization and dissociation of diatomic molecules induced by a weak field (after preliminarily populating an intermediate
level) and by intense, linearly polarized monochromatic radiation have been studied. Field-induced mixing of rotational components
of various electronic-vibrational states of molecules (such as CO, NO, etc.) at field strength f∼10−4–10−5 atomic units can lead to migration among states with different angular momenta J. Therefore, ions with rotational momenta J
+ much higher than those prescribed by selection rules for three-photon absorption can be formed from molecules in the ground
state. The possibility of selective formation of ions with J
+≫1 and zero projection of the angular momentum on the polarization vector of the external electromagnetic radiation has been
investigated.
Zh. éksp. Teor. Fiz. 111, 1624–1632 (May 1997) 相似文献
8.
We study the Dirac operator D
0 in an external potential V, coupled to a quantized radiation field with energy H
f and vector potential A. Our result is a Chernoff-type theorem, i.e., we prove, for the operator D
0+α · A+V +λ H
f with λ ∈{0, 1}, that the essential self-adjointness is not affected by the behavior of V at ∞.
相似文献
9.
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
10.
For a model of atoms and molecules made from static nuclei and non-relativistic electrons coupled to the quantized radiation
field (the standard model of non-relativistic QED), we prove a Mourre estimate and a limiting absorption principle in a neighborhood
of the ground state energy. As corollaries we derive local decay estimates for the photon dynamics, and we prove absence of
(excited) eigenvalues and absolute continuity of the energy spectrum near the ground state energy, a region of the spectrum
not understood in previous investigations. The conjugate operator in our Mourre estimate is the second quantized generator
of dilatations on Fock space.
Supported by NSERC under Grant NA 7901. 相似文献
11.
Optical-resonance-Raman scattering by acoustic phonons is used to study the effect of an electric field on the state of excitons
in GaAs/AlAs superlattices. When the energy of the exciting photon coincides with the energy of an exciton bound to Wannier-Stark
states of a heavy hole and electron with Δn=0,±1, the acoustic Raman scattering is enhanced. Oscillations in the intensity of the Raman spectrum in the electric field
are explained by resonance delocalization of the exciton ground state as it interacts with Wannier-Stark states of neighboring
quantum wells or with Wannier-Stark states of a higher electron miniband.
Fiz. Tverd. Tela (St. Petersburg) 40, 827–829 (May 1998) 相似文献
12.
M. Z. Smirnov 《Journal of Experimental and Theoretical Physics》1998,87(2):260-265
The nonlinear dynamics of an open quantum system consisting of a “dressed” atom, i.e., an atom coupled with an external multifrequency
electromagnetic field, and a single quantized mode of an electromagnetic field is studied. At different crossing points of
the quasilevels of the dressed atom, the average number of photons in the quantized mode may either increase without limit
with the passage of time or oscillate within finite limits. In the latter case a decrease of the number of photons is accompanied
by regularization of their statistics, which may become sub-Poissonian.
Zh. éksp. Teor. Fiz. 114, 474–483 (August 1998) 相似文献
13.
Volker Bach Jürg Fröhlich Israek Michael Sigal Avy Soffer 《Communications in Mathematical Physics》1999,207(3):557-587
In this paper we study the energy spectrum of the Pauli–Fierz Hamiltonian generating the dynamics of nonrelativistic electrons
bound to static nuclei and interacting with the quantized radiation field. We show that, for sufficiently small values of
the elementary electric charge, and under weaker conditions than those required in [3], the spectrum of this Hamiltonian is
absolutely continuous, except possibly in small neighbourhoods of the ground state energy and the ionization thresholds. In
particular, it is shown that (for a large range of energies) there are no stable excited eigenstates. The method used to prove
these results relies on the positivity of the commutator between the Hamiltonian and a suitably modified dilatation generator
on photon Fock space.
Received: 10 April 1998 / Accepted: 12 April 1999 相似文献
14.
G. E. Volovik 《JETP Letters》1999,70(9):609-614
The energy levels of fermions bound to the vortex core are considered for the general case of chiral superconductors. There
are two classes of chiral superconductivity: in the class I superconducting state the axisymmetric singly quantized vortex
has the same energy spectrum of bound states as in an s-wave superconductor: E=(n+1/2)ω0, with integral n. In class II the corresponding spectrum is E=nω0 and thus contains a state with exactly zero energy. The effect of a single impurity on the spectrum of bound states is also
considered. For class I the spectrum acquires the doubled period ΔE=2ω0 and consists of two equidistant sets of levels, in accordance with A. I. Larkin and Yu. N. Ovchinnikov, Phys. Rev. B 57, 5457 (1998). For the class II states the spectrum is not influenced by a single impurity if the same approximation is applied.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 9, 601–606 (10 November 1999)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
15.
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
16.
V. B. Timofeev A. I. Tartakovskii A. I. Filin D. Birkedal J. Hvam 《Physics of the Solid State》1998,40(5):767-769
Luminescence and luminescence excitation spectra are used to study the energy spectrum and binding energies of direct and
spatially indirect excitons in GaAs/AlGaAs superlattices having different electron and hole miniband widths in high magnetic
fields perpendicular to the heterolayers. The ground state of the indirect excitons formed by electrons and holes which are
spatially distributed among neighboring quantum wells is found to lie between the ground 1s state of the direct excitons and the threshold of the continuum of dissociated exciton states in the minibands. The indirect
excitons have a substantial oscillator strength when the binding energy of the exciton exceeds the scale of the width of the
resulting miniband. It is shown that a high magnetic field shifts a system of symmetrically bound quantum wells toward weaker
bonding. At high exciton concentrations, spatially indirect excitons are converted into direct excitons through exciton-exciton
collisions.
Fiz. Tverd. Tela (St. Petersburg) 40, 833–836 (May 1998) 相似文献
17.
The formation of radiating particles in the excitation of C60 fullerene molecules by electrons with energies E
e<100 eV is investigated by the method of crossed molecular and electron beams. A quasicontinuous (with a spectral resolution
of 3 nm) emission spectrum, close to the Planck emission spectrum of a heated body, is recorded in the wavelength range 300–800
nm. The temperature of the radiation corresponds to an internal energy of the C60 molecule of approximately 40 eV.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 12, 915–919 (25 June 1996) 相似文献
18.
The exact wave function for a one-dimensional chain of electrons coupled with squeezed phonons is obtained. The ground state
energy and the gap in the electron spectrum are calculated. It is shown that there exists an optimal phonon number n
ph≠0 for the ground state of the system. The results are generalized for a system of correlated electrons.
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 3, 140–145 (10 August 1996)
On leave from Institute of General and Inorganic Chemistry of the Russian Academy of Sciences, 31 Leninskii prosp., GSP-1,
Moscow, 117907, Russia
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
19.
The heating of electrons in an AlxGa1−x
As/GaAs (x>0.42) heterostructure in a lateral (directed along the heterointerfaces) electric field is studied. Population inversion
on the size-quantization subbands of the Γ valley of GaAs and a giant population inversion between the X-valley states of
AlxGa1−x
As and Γ-valley states of GaAs are predicted. The possibility of using these inversions for achieving stimulated IR emission
is discussed.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 1, 73–77 (10 July 1998) 相似文献
20.
Simple analytical expressions are obtained for the energy and angular distributions of outgoing electrons in ionization of
a molecular hydrogen ion by a strong low-frequency electromagnetic field as well as for the ionization probabilities per unit
time. The cases of linear and circular polarization of the laser radiation are studied. It is shown that in contrast to the
case of the ionization of atoms oscillations appear in the energy spectra of the photoelectrons as a function of their kinetic
energy. The well-known limits for the tunneling ionization probabilities for the hydrogen atom by a strong low-frequency alternating
field are obtained in the case of large internuclear separations.
Zh. é ksp. Teor. Fiz. 113, 583–592 (February 1998) 相似文献