Vol. 48, No. 4 (1999)
1999, 48 (4): 561-565. doi: 10.7498/aps.48.561
Based on the previous paper, for accelerating charge in general relativity, we obtained the exact expressions of electromagnetic field and radiating energy.
1999, 48 (4): 566-574. doi: 10.7498/aps.48.566
Stationary solutions of one-dimensional hydrogen atom are two-degree degenerate. Three kinds of typical solutions can be constructed from those degenerated solutions. They correspond to three kinds of ensembles. Double-wave theory describes a single hydrogen atom. When three different averages over ensembles are made for double-wave theory, three kinds of typical solutions in the usual quantum mechanics are obtained. A comparison between these solutions and those of classical mechanics is made.
1999, 48 (4): 575-580. doi: 10.7498/aps.48.575
By means of the Newman-Penrose formalism,the gravitational,electromagnetic, scalar and Dirac fields in spherically symmetric non-static space-times are discussed.It is shown that the quantum ergosphere can influence the radiative mechanism of a non-static black hole.The character of the effect is that the radiative mechanism is obviously dependent on the spin state,which differs from the classical effects due to the Kerr ergosphere and the electromagnetic potential.
1999, 48 (4): 581-588. doi: 10.7498/aps.48.581
Firstly, we find out the convergent scope in limited time of the conservation flow x…+x·-x2+B=0 (0≤B≤0.005) in a certain time, whose scope Lyapunov exponents is below zero, and restrained in Poincaré section, and then get the steady periodic orbits through periodic pulse method. With the above-mentioned rule, we can control systematic high periodic orbits.This rule is, to some extent, robust against external noise.
1999, 48 (4): 589-595. doi: 10.7498/aps.48.589
The method of Lengthening time of autocorrelation of signal is used to control hyperchaotic behavior in nonlinear continuous system. The Rossler and CLHE hyperchaotic system are taken as two typical examples. The numberical simulations show that the behavior of hyperchaos in a nonlinear system is controlled effectively and a series of stable periodic orbits are obtained by the method in this paper. The choice of control parameter is independent of controlled hyperchaotic systems in principle.
ATOMIC AND MOLECULAR PHYSICS
1999, 48 (4): 596-602. doi: 10.7498/aps.48.596
The rates of blackbody rediation induced transitions and spontaneous transitions of Rydberg states and Stark states of ytterbium have been calculated by the method of numerical integration based on the hydrogenic model. The calculated results are compared with experimental data measured by using delayed electric field ionization. In addition, we have chosen the typically initial states to observe the distribution of repopulations among nearby states and given theoretical explanation. The availability of the hydrogenic model when applied to highly-excited states of complex atoms is discussed.
1999, 48 (4): 603-610. doi: 10.7498/aps.48.603
Spontaneous emission from a three-level atom in a photonic crystal is investigated. As a result of quantum interference and photon localization, the populations in the two upper levels displays oscillatory or quasioscillatory behavior. This depends on the relative positon of the two upper levels from forbidden gap and the initial state of atom. These Properties differ from those of three-level atom in vacuum.
A new nanometer lithographic techniqueatom lithography,which is developed based on the principles of laser cooling and trapping of neutral atomsthe newest achievements of quantum optics,has been reviewed.The working principles,the overall schemes,the individual techniques and the acquired results are described.This new method has been compared with the existing micro-lithographic techniques,and the application potentialities in the micro-electronics and other fields have been discussed.
1999, 48 (4): 620-627. doi: 10.7498/aps.48.620
For a TbFeCo quadrilayer illuminated by laser beam,absorption of the laser power within different layers was considered by analysizing the rate of absorption of energy per unit volume.With the help of implicit method,the profile of temperature of the multilayer was given and the diffusion of heat was studied.The effect of laser power,laser duration and the convection loss at the front surface upon the thermal characteristics of the multilayer was investigated.This thermal analysis procedure provided a good example for the thermal investigation within other optical disk systems.
1999, 48 (4): 628-632. doi: 10.7498/aps.48.628
Based on the Berakdar theory,this work investigates theoretically the triply differential cross sections for electron impact ionization of Li+(1s2) at an energy of 100eV in coplanar doubly symmetric geometry,i.e.,equal energies and equal emission angles for the two electrons in the final state.Dominant ionization mechanisms are identified and the contribution of different scattering amplitudes and the major role of initial channel Coulomb field are discussed.It turns out that the cross section in doubly symmetric geometry is strongly influenced by the interference of these amplitudes and the initial channel Coulomb field.
1999, 48 (4): 633-641. doi: 10.7498/aps.48.633
We have studied the electronic structure of M@C28(M=Ti,Zr,Hf) endohedral complexes with ab initio method in B3-LYP effective core potential model and density functional theory.The computations were carried out for the geometry optimizations,which determined the structure constants of atoms in ground states,and the analysis of natural bond orbital.The interaction of Ti atom and C28 cluster was very different from that of Zr (or Hf) atom and C28 cluster. It occurred on the atomic configuration,the bonding character and the distribution of electronic states etc.According to the estimation of binding energy,three complexes could exist stably,and Zr@C28 and Hf@C28 were more stable than Ti@C28.The results have been analyzed and discussed,also compared with those in the literatare.
1999, 48 (4): 642-649. doi: 10.7498/aps.48.642
We investigated the energy,structure and related topological property of beryllium clusters bound by a recently developed first-principles many-body potential(Estela Blaisten-Barojas and S.N.Khanna,Phys.Rev.Lett.,61(1988),1477).A modified cluster structure optimization method based on the genetic algorithms was used to search for the global minimum of the potential.Dependence of the energy,structure and related topological property of beryllium clusters Ben(n=2—25) on cluster size was elucidated;and a systematic structure comparison of Ben with metal cluster Mn and rare-gas cluster LJn bound by long-range Morse potential and Lennard-Jones potential,respectively,was presented.Our results showed that structures of Ben,in the range of n=2—25,can be categorized as either Mn-like or LJn-like,and many-body contributions of the potential appears to play a significant role in determining the most stable structures in beryllium systems.
CLASSICAL AREA OF PHENOMENOLOGY
1999, 48 (4): 650-660. doi: 10.7498/aps.48.650
Electron dynamics in the extra-intense stationary laser field has been investigated by numerical simulation method.It is found,for the first time to our knowledge,that when Q100(Q=eE/mecω,is a dimensionless parameter measuring the field intenstiy),the electron with relatively lower energy can be captured and violently accelerated by the laser beam.This is a new phenmenon which is of potential importance to the far-field laser acceleration in vacuum.
1999, 48 (4): 661-666. doi: 10.7498/aps.48.661
Realization of a spin-type Greenberger-Horne-Zeilinger state via the Jaynes-Cummings model with large detuning is presented.The contradiction to local hidden variable theory is made through measuring the parity of the cavity fields. This scheme does not violate Bell's inequality.
A NEW CONFIGURATION OF THE LASER CAVITY FOR SIMULTANEOUS DUAL WAVELENGTH Q-SWITCH PULSED Nd∶YAlO3 LASER
1999, 48 (4): 667-672. doi: 10.7498/aps.48.667
Based on the rate equations of the Q-Switch simultaneous dual wavelength laser (SDWL) of Nd∶YAlO3 (Nd∶YAP), we have developed a new configuration of the cavity by adjusting the ratio of the cavity lengths for lasers with different wavelengths according to their emission cross sections. Therefore the competition ability and the net gain for the two different wavelengths will be equal at any time and anywhere in the laser rod, and the optimal spatial and temporal overlap of the different wavelengths can be easily realized for optimal sum frequency mixing. Besides, this configuration can overcome several disadvantages of the previously used configurations, and its photon density product integral of the two different wavelengths is about one order larger than the previous ones.
1999, 48 (4): 673-684. doi: 10.7498/aps.48.673
Theoretical analysis and numerical solution of several physical mechanisms on nondegenerate four-wave mixing(NDFWM) in semiconductor laser amplifiers are presented. Starting from the general carrier rate equation, density-matrix equations and nonlinear wave equations, considering the effects of carrier-density pulsations, carrier heating, and spectral-hole burning, we obtained three sets of nonlinear coupled wave equations, and compared the contributions of the three different physical mechanisms to the NDFWM. We also investigated the effect of linewidth enhancement factor on the conversion efficiency of the NDFWM in semiconductor laser amplifiers.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
MULTI-VARIABLE FEED-BACK CONTROL OF PLASMA CURRENT AND HORIZONTAL POSITION IN HT-7 SUPER-CONDUCTIVE TOKAMAK
1999, 48 (4): 685-691. doi: 10.7498/aps.48.685
In the analysis of HT-7 superconductive tokamak which consists of iron core, thick copper shell and multi-coupling coils system, the electromagnetic parameters are linearized by a novel method; the copper shell is replaced by an equivalent pair of coils in series-opposing; and the multi-coupling is compensated by an intermediate state variable. As a result, the plasma control equation can be set up and solved more simply and easily. The feed-back control system has been designed and rather good results were obtained in experiment. This feed-back control system has high response speed, less computing time and is easy to carry out.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
INTERNAL FRICTION BEHAVIOR OF THE STANDARD ANELASTIC SOLIDS IN LOW FREQUENCY INTERNAL FRICTION MEASUREMENT
1999, 48 (4): 692-698. doi: 10.7498/aps.48.692
Internal friction behavior of the standard anelastic solid has been described by τσ (the relaxation time at constant stress) and τε (the relaxation time at constant strain) of a three-parameter mechanical model. The effect of the inertia member in a vibration system on the internal friction values measured is not avoidable in a forced vibration experiment. When the measured internal friction values of a material are larger and the measuring frequency and resonant frequency of the vibration system are comparable to each other, the effect of the inertia member of the vibration system cannot be neglected.
1999, 48 (4): 699-703. doi: 10.7498/aps.48.699
The molecular orbits of CO are rearranged under the strong influence of coadsorbed Cs atoms.The peak for CO on clean Ru(1010) surface,at 7.5eV BE attributed to the 5σ and 1π orbits,is split into two peaks with one at 6.3eV BE and the other at 7.8eV BE.The former peak shows an anti-symmetry character about the plane parallel to the crystallographic direction in the surface.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
1999, 48 (4): 704-712. doi: 10.7498/aps.48.704
By considering the anisotropy in the quasi-two-dimensional Cu—O plane for the cuprate compound,on the basis of the two-dimensional bisoliton model estabished,the nonlinear local coupling efects caused by the interactions between electrons and phonons in the strongly anisotropic Cu—O plane are investiged.The formation of bisoliton and its bound states are discussed.The periodic bisoliton solution is given in the form of conoidal elliptic integral.The pairing energy for the two quasi-particles,the effective mass and the stability of the bisoliton are analysed in terms of the anisotropy.
1999, 48 (4): 713-720. doi: 10.7498/aps.48.713
By using a simple tight-binding model,we study the magnetic properties of the substituted polyacetylene with lateral radicals R*.It includes the effects of π electron hopping between the alternate radicals and associated carbons on the bond order wave along the polyacetylene chain,the formation of charge density wave,and the effects of next-nearest-neighbor hoppings and electronic interactions.Our results are compared with and used to understand the ab initio calculations on the organic ferromagnet(C3H3)n,substituted polyacetylene with lateral radical R* as the organic segment CH2.
1999, 48 (4): 721-728. doi: 10.7498/aps.48.721
By using frequency and time domain dielectric spectroscopy, the polar phase transitions of (Ba1-xSrx)TiO3 ceramics have been studied. Compared with the phase transitions of a ferroelectric crystal, the motion of space charges in ceramic has been obtained as well as lattice softening, excitation of screen charges and motion of ferroelectric domains. Slow effect, which is contributed by ferroelectric domains and space charges, can affect the accurate measurement by frequency domain method. In this paper we describe this influence and explain some experimental results. The reciprocal of frequency domain dielectric constant has a linear softening in the transition of primary structure, but has a parabolic type softening in that of high structure.
1999, 48 (4): 729-734. doi: 10.7498/aps.48.729
According to the relationship of Wang and Zunger between the declectric constants and the radius of a CdSe quantum dot (QD),we use the variational method to calculate the binding energy and ground state energy of an exciton in the QD.Compared with the previouse calculations,the present result shows that the binding energy increases while its ground state energy becomes lower and it is close to the experimental value.
1999, 48 (4): 735-743. doi: 10.7498/aps.48.735
We study the detection theory of polydispersities for dilute suspension of optical and size polydisperse spherical particles， for which the Rayleigh-Gans-Debye (RGD) approximation is valid.To develop the theory a concentric core-shell hard sphere model is adopted,in which particles possess a continuous variation in the core size and shell thickness,the latter is directly proportional to the radius of core,thus giving rise to a distribution in the particle refractive indices.We assume the shell thickness to be L=αR,where αm(K) is derived. We analyse the dependence of the average scattered intensity I(q) and the effective diffusion coefficient De(q) which is obtained from the first cumulant measured by dynamic light scattering in the case that the refractive index of the solvent and that of the shell are matched,i.e.,nm=ns, on the scattering vector q.A linear relation between the extreme point of the effective diffusion coefficient and the polydispersity δ is obtained, which gives a method to detect the small size polydispersities of a disperse system.
1999, 48 (4): 744-750. doi: 10.7498/aps.48.744
Using a newly-developed population mixing technique we have studied the exciton dynamics in self-organized InAs/GaAs quantum dots (QDs).It is found that the exciton lifetime in self-organized InAs/GaAs QDs is around 1ns, almost independent of InAs layer thickness.The temperature dependence of the exciton lifetime varies from sample to sample,but no obvious experimental evidence was found that the lifetime is related to the δ-function of density of states in QDs.We have also found that the population mixing technique can be used to directly reveal the band-filling effect in the excited states of the QDs.
INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
1999, 48 (4): 751-756. doi: 10.7498/aps.48.751
The coupled soliton solutions of nonlinear Schrdinger equations for describing the alpha-helix protein are obtained, and their physical meaning is discussed.
1999, 48 (4): 757-762. doi: 10.7498/aps.48.757
The step magnetization is observed in spin glass manganites La0.67Ca0.33(Mn,Fe)O3, and the colossal magnetoresistance larger than 104%(ΔR/RH) is obtained near the critical field.The micro-origin of the novel step magnetism is attributed to the melting of antiferromagnetic clusters in the applied magnetic field.
1999, 48 (4): 763-768. doi: 10.7498/aps.48.763
Tunneling giant magnetoresistance(TGMR) in Fe-Al2O3 granular films which were prepared by co-sputtering have been reported.MR ratio of the film with Fe volume fractions fV≈0.45 takes a maximum of 4.4% at room temperature when a magnetic field of 1T was applied parallel to the film plane,accompanying huge specific electrical resistivities of the order of 105 μΩ·cm.Field dependence of the MR is well described by the form proportional to the square of the magnetization of the film.Temperature dependence of the MR ratio of the film has also been investigated.The MR exhibits strong temperature dependence.The MR below 50K remarkably increases with decreasing temperature resulting in MR＝14.9% and 26% at 20 and 4.2K，respectively.The anomalous increase of the MR at low temperature seems to arise from the successive onset of higher-order processes of spin-dependent tunneling between large granules through intervening small ones with strong Coulomb blockade.