共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
On the basis of the analysis of absorption spectra of Er3+:PbMoO4 crystals made for the transitions from the ground 4 I 15/2 state to excited states of Er3+ ions by the Judd-Ofelt method, the main spectroscopic characteristics of the crystals were obtained, including the transition probabilities and the radiative lifetimes. 相似文献
3.
Hock KM 《Chaos (Woodbury, N.Y.)》1996,6(4):564-567
The Euler problem with two fixed point masses and one moving mass is reconsidered in the light of general relativity. The scattering of a particle by two fixed black holes is shown to be strongly chaotic. Two neutral black holes have been used for the study. The particle trajectories have been computed numerically using a modified muffin tin approximation. A plot of the scattering angle against impact parameter showing distinct signs of chaos is presented. (c) 1996 American Institute of Physics. 相似文献
4.
We analyse the existence of symmetric periodic orbits of the two-electron atom. The results obtained show that there exist six families of periodic orbits that can be prolonged from a continuum of periodic symmetric orbits. The main technique applied in this study is the continuation method of Poincaré. 相似文献
5.
We demonstrate the existence of stable nondispersing two-electron wave packets in the helium atom in combined magnetic and circularly polarized microwave fields. These packets follow circular orbits and we show that they can also exist in quantum dots. Classically the two electrons follow trajectories which resemble orbits discovered by Langmuir and which were used in attempts at a Bohr-like quantization of the helium atom. Eigenvalues of a generalized Hessian matrix are computed to investigate the classical stability of these states. Diffusion Monte Carlo simulations demonstrate the quantum stability of these two-electron wave packets in the helium atom and quantum-dot helium with an impurity center. 相似文献
6.
The method of numerical integration of the classical equations of motion was used to study interaction of a model two-electron atom with ultrashort laser pulses. Mechanisms and specific features of the ionization process were analyzed in a broad range of laser-field parameters. 相似文献
7.
R. J. Yaüez A. R. Plastino J. S. Dehesa 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,56(1):141-150
We investigate the entanglement properties of bound states
in an exactly soluble two-electron model, the Moshinsky atom.
We present exact entanglement calculations for
the ground, first and second excited states of the system.
We find that these states become more entangled when the
relative inter-particle interaction becomes stronger. As a general
trend, we also observe that the entanglement of the eigenstates
tends to increase with the states’ energy. There are, however,
“entanglement level-crossings” where the entanglement of a state
becomes larger than the entanglement of other states with higher
energy. In the limit of weak interaction, we also compute (exactly)
the entanglement of higher excited states. Excited states with
anti-parallel spins are found to involve a considerable amount of
entanglement even for an arbitrarily weak (but non zero)
interaction. This minimum amount of entanglement increases
monotonically with the state’s energy. Finally, the connection
between entanglement and the Hartree-Fock approximation in the
Moshinsky model is addressed. The quality of the ground-state
Hartree-Fock approximation is shown to deteriorate, and the
corresponding correlation energy to grow, as the entanglement of the
(exact) ground state increases. The present work goes beyond
previous related studies because we fully take into account the
identical character of the two constituting particles in the
entanglement calculations, and provide analytical, exact results
both for the ground and the first few excited states. 相似文献
8.
D. U. Matrasulov 《Physics of Atomic Nuclei》2001,64(2):253-255
Stochastization of a supercritical atom (with a nuclear charge number Z in excess of 137) under the effect of a periodic perturbation is investigated. The Hamiltonian for a relativistic electron in the Coulomb field of a Z>137 charge is obtained. A simple analytic formula is derived for the critical external-field strength corresponding to the onset of stochastization. The diffusion coefficient is evaluated. 相似文献
9.
J. G. Mahecha 《Few-Body Systems》1989,6(4):183-192
Three rigid-body solutions for a rotating two-electron atom under the influence of an electric field along the rotation axis have been obtained within a classical approach. One exact solution gives in the zero-field case a previous result known as a rotor, another exact solution in the zero-field case gives the Wannier unbound solution, and a numerical solution in the zero-field case gives the asymmetric top or Langmuir solution. The stability analysis of the linearized motions around each of the equilibrium configurations was made for different values of the electric field. We find critical values of the electric field beyond which no equilibrium exists. Values for the classical polarizability of rotating H– and He are reported. 相似文献
10.
A.L. Stewart 《物理学进展》2013,62(47):299-353
11.
The general relativistic Dirac equation is formulated in an arbitrary curved space-time using differential forms. These equations are applied to spherically symmetric systems with arbitrary charge and mass. For the case of a black hole (with event horizon) it is shown that the Dirac Hamiltonian is self-adjoint, has essential spectrum the whole real line and no bound states. Although rigorous results are obtained only for a spherically symmetric system, it is argued that, in the presence of any event horizon there will be no bound states. The case of a naked singularity is investigated with the results that the Dirac Hamiltonian is not self-adjoint. The self-adjoint extensions preserving angular momentum are studied and their spectrum is found to consist of an essential spectrum corresponding to that of a free electron plus eigenvalues in the gap (–mc
2, +mc
2). It is shown that, for certain boundary conditions, neutrino bound states exist.Supported in part by the National Science Foundation 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.
In this review we discuss the chaotic dynamics (both classical and quantal aspects) of a simple atomic system, namely hydrogen
atom interacting with time independent and time dependent external fields. These include: i) static electric field, ii) static
magnetic field, iii) combined electric and magnetic fields, in parallel and perpendicular configuration, iv) instantaneous
and generalized van der Waals field, v) mass anisotropy and vi) linearly and circularly polarized microwave fields. 相似文献
14.
We consider the 3-body problem in relativistic lineal [i.e., (1+1)-dimensional] gravity and obtain an exact expression for its Hamiltonian and equations of motion. While general-relativistic effects yield more tightly bound orbits of higher frequency compared to their nonrelativistic counterparts, as energy increases we find in the equal-mass case no evidence for either global chaos or a breakdown from regular to chaotic motion, despite the high degree of nonlinearity in the system. We find numerical evidence for mild chaos and a countably infinite class of nonchaotic orbits, yielding a fractal structure in the outer regions of the Poincaré plot. 相似文献
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16.
D. U. Matrasulov 《Technical Physics》1999,44(2):249-251
The stochastic ionization of a relativistic hydrogenlike atom in a monochromatic field is investigated. Using Chirikov’s criterion
for stochasticity, an analytical formula is obtained for the critical value of the external field for which stochastic ionization
of a relativistic atom occurs.
Zh. Tekh. Fiz. 69, 127–129 (March 1999) 相似文献
17.
E. A. Volkova V. V. Gridchin A. M. Popov O. V. Tikhonova 《Journal of Experimental and Theoretical Physics》2004,99(2):320-327
Direct numerical simulations are performed to analyze stabilization of a two-electron model atom in a strong electromagnetic field. The system is found to be stabilized with respect to both single and double ionization. By comparing the present results with those concerning stability of one-electron atoms, it is shown that stabilization is due to the formation of a Kramers-Henneberger two-electron atom. Ionization and stabilization characteristics of excited singlet and triplet states of an atomic system are examined. 相似文献
18.
《Physics letters. A》1998,243(4):195-204
A manifestly relativistically covariant form of the van der Pol oscillator in 1 + 1 dimensions is studied. We show that the driven relativistic equations, for which x and t are coupled, relax very quickly to a pair of identical decoupled equations, due to a rapid vanishing of the “angular momentum” (the boost in 1 + 1 dimensions). A similar effect occurs in the damped driven covariant Duffing oscillator previously treated. This effect is an example of entrainment, or synchronization (phase locking), of coupled chaotic systems. The Lyapunov exponents are calculated using the very efficient method of Habib and Ryne. We show a Poincaré map that demonstrates this effect and maintains remarkable stability in spite of the inevitable accumulation of computer error in the chaotic region. For our choice of parameters, the positive Lyapunov exponent is about 0.242 almost independently of the integration method. 相似文献
19.
The magnetic and electric polarization fields of a relativistic hydrogen atom in a solid are analyzed. At atomic distances, these fields differ only slightly from the corresponding fields of an ionized atom. 相似文献
20.
A. Derevianko W. R. Johnson V. D. Ovsyannikov V. G. Pal’chikov D. R. Plante G. von Oppen 《Journal of Experimental and Theoretical Physics》1999,88(2):272-277
We use the relativistic configuration-interaction method and the model potential method to calculate the scalar and tensor
components of the dipole polarizabilities for the excited states 1s3p
3
P
0 and 1s3p
3
P
2 of the helium atom. The calculations of the reduced matrix elements for the resonant terms in the spectral expansion of the
polarizabilities are derived using two-electron basis functions of the relativistic Hamiltonian of the atom, a Hamiltonian
that incorporates the Coulomb and Breit electron-electron interactions. We formulate a new approach to determining the parameters
of the Fuss model potential. Finally, we show that the polarizability values are sensitive to the choice of the wave functions
used in the calculations.
Zh. éksp. Teor. Fiz. 115, 494–504 (February 1999) 相似文献