Vol. 47, No. 9 (1998)
1998, 47 (9): 1409-1415. doi: 10.7498/aps.47.1409
For a general KdV soliton solution and a general KdV-Burgers traveling wave solution,the direct perturbation method is used to construct their general perturbed corrections.Theoretical analysis reveals that the solution possesses conditional stability,namely,their stability depends sensitively on the physical parameters and initial conditions of the corresponding system.The results have extended and corrected some assertions of instability in the recent articles.
1998, 47 (9): 1416-1420. doi: 10.7498/aps.47.1416
By using the homogeneous balance method,we give multiple soliton solutions of the approximate equations of long water wave.The method used herein can be generalized to the study of a class of nonlinear evolution equations.
1998, 47 (9): 1421-1426. doi: 10.7498/aps.47.1421
In this paper,the effect of the anisotropy diffusion on the growth of diffusion-limited aggregation(DLA) clusters is discussed.Our computer simulation results verify that DLA clusters grown with anisotropic diffusion rules have a striking overall diamond shape.A new anisotropic diffusion equation of particles is derived.The Hausdorff dimension of a two-dimensional DLA cluster in the anisotropic diffusion is calculated.The results show that the effective angle βeff=min(βix,βiy).In addition,the generalized dimension Dq of the anisotropic diffusion DLA is also discussed and an expression of the generalized dimension Dq is obtained using the modified wedge model.
1998, 47 (9): 1427-1435. doi: 10.7498/aps.47.1427
The aggregation in ultra-thin films is simulated.The growth morphologies,such as the fractal growth of clusters and the “step-flow”,are obtained.The relation between the density of the clusters and the bias angle of vicinal surface is analyzed,and the threshold value of step-flow and the fractal dimensions of the clusters are also calculated.The simulation results are consistent with the experiments.
1998, 47 (9): 1436-1449. doi: 10.7498/aps.47.1436
Atomic clock is an extremely precise oscillator,but the increase of precision of it is limited by the noise in it.The period and chaos in an atomic clock is simulated by using a type of Duffing equation.Statistical characteristis of various chaos are discussed.According to the Lyapunov exponent of the atomic clock signal,the chaos in the clock and its motivational mechanism is analyzed.Measured data from CSAO Laboratory during 1994.6.1—8.20 are processed and statistical characteristics of chaos described.
1998, 47 (9): 1450-1457. doi: 10.7498/aps.47.1450
Electric microfields inside or outside charged latex particles(0.31μm) and fine structure of magnetic domains in a permalloy film,are investigated by digital reconstruction from electron holograms.Resolution is improved by means of noise-filtering and phase-difference-amplification.Some new results are reported.
ATOMIC AND MOLECULAR PHYSICS
1998, 47 (9): 1458-1464. doi: 10.7498/aps.47.1458
This paper derives the equation of motion followed by the induced polarization of the two-level atoms subject to the laser field with frequency much lower than that of the transition between the levels.With the approximate solution to the equation of motion under the conditions of the weak external field and of the ultra-intense one,we obtain the characteristics of the corresponding high-order harmonics from the two-level atoms.
1998, 47 (9): 1465-1469. doi: 10.7498/aps.47.1465
The multiphoton ionization spectrum of methyl iodide is studied in the 440—510nm region.Three-photon is just resonant with the high-frequency tail of the (5pπ,6p) Rydberg state of methyl iodide.Then the excited methyl iodide continually absorbs another photon to be ionized and dissociated into fragment ions.
1998, 47 (9): 1470-1476. doi: 10.7498/aps.47.1470
The (2+1) resonance-enhanced multiphoton ionization (REMPI) spectra of the CF2Cl radicals, which are generated by a pulsed dc discharge,were investigated between 332 and 362nm.Two new Rydberg states,4s and 4p,were observed and indentified.The observed states and spectroscopic constants include 4s Rydberg state (band origin ν0—0=55371cm-1,ω3′ (CF2 scissors)=523±7cm-1,ω′4 (OPLA,i.e.,out-of-plane bending mode)=734±4cm-1) and 4p Rydberg state (ν0—0=57601.3cm-1,ω3′=552±10cm-1,ω4′=762±12cm-1).The quantum defect values of 4s and 4p Rydberg states were also estimated.It seems that the radical production by a pulsed dc discharge combined with PEMPI technique is a powerful tool to study the electronic state of radicals.
CLASSICAL AREA OF PHENOMENOLOGY
PREPARATION OF TWO-MODE SCHR?DINGER-CAT STATES VIA ATOMIC NON-RESONANT INTERACTION WITH TWO-MODE FIELD
1998, 47 (9): 1477-1480. doi: 10.7498/aps.47.1477
A method for the generation of two-mode Schrdinger-cat states via non-resonant interaction of Ξ-type three-level atom with two-mode field is presented.
QUANTUM DYNAMICS OF A CASCADE THREE-LEVEL ATOM INTERACTING WITH COHERENT STATE IN THE COUNTER ROTATING WAVE APPROXIMATION
1998, 47 (9): 1481-1488. doi: 10.7498/aps.47.1481
The dynamics of a cascade three-level atom interacting with the single mode coherent state under the Counter-Rotating-Wave approximation (C-RWA) is investigated.The properties of the mean-photon number (N(t)) and the degree of second-order coherence (g2(t)) are analyzed in this model.The little indentation which represents the quantum noise of the system appears in the evolution curves of the mean-photon number and the degree of second-order coherence under the C-RWA.The quantum noise which is caused by the virtual photon field gradually becomes weak when ω increases.The quantum noise increases when increases.The anti-bunching effect of the system under the C-RWA is stronger than the one under the RWA.Besides,the relation of N(t) and g2(t) with the atom-field coupling constant λ is revealed in our results.
ADIABATIC TRANSITION TRANSFER PHENOMENON OF ELECTRONS AND THE QUANTUM STATISTICAL PROPERTIES OF LIGHT FIELD IN A KERR MEDIUM
1998, 47 (9): 1489-1497. doi: 10.7498/aps.47.1489
We first derive the state vector of a cascade three-level atom interacting with pair coherent states in a kerr medium.It is shown by numerical calculations that the Kerr effect results in the adiabatic transition transfer phenomenon of electrons,and the superstructures in the long-time behavior of the quantum statistical properties of light field appear.
OBSERVATION OF INTENSITY SQUEEZING AND LARGE PHASE NOISE REDUCTION IN SELF-LOCKED SEMICONDUCTOR LASERS
1998, 47 (9): 1498-1503. doi: 10.7498/aps.47.1498
Both intensity squeezing and dramatic phase noise reduction have been obtained with a confocal cavity used to feedback the beam from the quantum well diode laser.We have measured an intensity squeezing of 19.3%(37.8% inferred at the laser output) around 35MHz and achieved phase noise reduction of 40—25dB from 9kHz to 100MHz.Quasi-minimum uncertainty state have been demonstrated.
1998, 47 (9): 1504-1508. doi: 10.7498/aps.47.1504
The analytical formulas of laser threshold,slope efficiency of a three-energy-level system are deduced from rate-equations of transitions.The absorption cross section of Er3+ ions in YAG crystal is calculated according to measured absorption spectrum.The characteristics of laser at 1.6μm wavelength are analysed.
1998, 47 (9): 1509-1514. doi: 10.7498/aps.47.1509
Steady-state dark (bright)spatial solitons are predicted for biased photovoltaic photorefractive materials,which are due to the photovoltaic effect and spatially nonuniform screening of the external bias field. These solitons differ from previously observed steady-state photorefractive spatial solitons in their properties and physical origin.If the applied field is strong enough, these solitons are just like the screening solitons. If the applied field is absent, these solitons degenerate into the photovoltaic solitons under the close-circuit condition.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
1998, 47 (9): 1515-1519. doi: 10.7498/aps.47.1515
A new approach is presented to produce core plasma poloidal rotation during electron cyclotron resonance heating (ECRH) in Tokamaks. The physical mechanism employed here is as follows:in a Tokamak plasma with high power ECRH, the resonance particle localization causes poloidal electric field, which consequently induce a poloidally asymmetric ion profile. This kind of poloidal ion accumulation would overwhelm the damping of poloidal rotation from the magnetic pumping, and make the plasma spin up poloidally. Based on the fluid equations and the drift kinetic equation, we have derived the criterion of plasma spin up in the collisionless region. It is shown that the core plasma poloidal rotation can be generated by ECRH in the practical rf power level.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
1998, 47 (9): 1520-1528. doi: 10.7498/aps.47.1520
A new method for determining the separate temperature factors (STF) for different atoms in two-atom compound crystals is put forward. Using the characteristics of resonant X-ray dynamical diffraction by perfect crystals near the atomic absorption edge,two equations of STF are derived. As the parameters in the equations can be obtained from experimental measurement and theoretical calculation, STF can be determined by solving the equations. We applied this method to a perfect crystal GaAs at 300K, and obtained BGa=0.4573×10-20m2,BAs=0.7339×10-20m2. This method may be extended to the cases of multi-atom compound crystals.
The microstructure of silicon nitride thin film prepared by ECR-PECVD is studied by transmission electron microscopy (TEM), scanning tunnel microscopy (STM) and PDS microphotometer. The results indicate that the Si3N4 thin film prepared by ECR-PECVD at lower temperature is the nano-Si3N4 thin film , the crystalline grain size lies between 14 to 29nm ,and this kind of Si3N4 thin film has fine surface planeness. We analyzed the mechanism of the formation of crystalline Si3N4 thin film at lower deposition temperature.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
1998, 47 (9): 1536-1541. doi: 10.7498/aps.47.1536
The effect of electric field on the luminescence and exciton in polymer is studied in two aspects: 1. In strong electric field, the exciton is dissociated into a pair of positive and negative polarons. This dissociation can quantitatively indicate the electric-field-induced luminescence quenching in electroluminescent polymer m-LPPP observed recently. 2. The π electrons in polymer possess delocalization, they are easily polarized. It is shown that the exciton in polymer has huge polarizability, which is 103 times larger than that of hydrogen atoms.
MICROSTRUCTURES OF THE MICRO-CRYSTALLINE SILICON THIN FILMS PREPARED BY HOT WIRE CHEMICAL DEPOSITION WITH HYDROGEN DILUTION
1998, 47 (9): 1542-1547. doi: 10.7498/aps.47.1542
Microcrystalline silicon thin films were prepared by hot wire chemical vapor deposition with hydrogen dilution. Structures of the films were examined by Raman scattering, Fourier transform infrared (IR) and small angle X-ray scattering (SAXS)etc. It is shown that with increasing flow ratio RH=H2/(H2+SiH4) the volume fraction of crystalline increases while the hydrogen content decreases. The result from SAXS indicates that with increasing dilution ratio, the density of the film is increased, which implies the volume fraction of micro-voids is reduced. Combining with the data from IR and SAXS, we conclude that SiH2 vibration mode in hydrogenated microcrystalline silicon thin film is located at the grain boundaries rather than in the internal surface of the micro-voids.
1998, 47 (9): 1548-1554. doi: 10.7498/aps.47.1548
The first-order structure of a polymer is an ideally perfect long molecule chain; electrons and ions in it make contribution to the fast polarization effect. The topological deformation of the long chain gives second-order structure, and the third-order structure consists of many deformed chains; both second and third-order structures of a polymer make contribution to the slow polarization. The frozen time domain dielectric spectroscopy method shows that in β transition of a polymer, the second- and thire-order structures will be softened but the first-order one does not change. Using this method, the slow and fast components of frozen polarizations in polymer can be kept apart.
1998, 47 (9): 1555-1563. doi: 10.7498/aps.47.1555
A new method to calculate the effective optical constants of the coatings with particles is presented. Considering the light absorption and scattering of the sphere, cylinder, and sheet shaped particles in the coatings, we obtain the apparent reflectivity of the coatings. Let this reflectivity equal to the reflectivity of other suppositional homogeneous coating, the effective optical constants of the coating with particles are calculated.
INVESTIGATION OF TENSILE-STRAINED,LONG WAVELENGTH In1-xGaxAsyP1-y/InP WITH QUANTUM-WELL STRUCTURE BY PHTOLUMINESCENCE MEASUREMENTS
1998, 47 (9): 1564-1570. doi: 10.7498/aps.47.1564
The Photoluminescence (PL) Spectra and the double-Crystal X-ray diffraction rocking curves from tensile-strained quantum materials with 2 and 3 wells are reported in this paper.They indicate that PL peaks result from the intrinsic recombination mechanisms between the electrons in the first conducting subband and the holes in the first light,heavy hole subband in the quantum well materials.We have analysed the variation of the twin-peak intensity ratio with temperature theoretically.The calculation result for No.577 and No.572 is basically in agreement with the measured one.The approximate relation of the split value ΔE1 of light-heavy hole subband with the mismatch rate ε is found.The difference of the theoretic calculation value and the measured result for the split value from the first light hole subband and the first heavy hole one is discussed.
INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
MICROSTRUCTURE CHARACTERISTICS AND THE GRAVITY INFLUENCE FOR UNIDIRECTIONALLY SOLIDIFIED Zr65Cu17.5Ni10Al7.5 ALLOY
1998, 47 (9): 1571-1578. doi: 10.7498/aps.47.1571
This paper studies the phase morphologies of glass-forming Zr65Cu17.5Ni10Al7.5 alloy during unidirectional solidification, as well as the gravity influence on them. The direction of the microstructure became worse when the moving speed of the furnace exceeded a critical value. This critical speed was about 5mm/min for Zr65Cu17.5Ni10Al7.5 alloy in the present experiments. Different relationship between the direction of the movement of the solid-liquid interface and the gravity field led to different states of buoyancy convection, and finally different phase morphologies were obtained. When the movement direction was the same as the gravity vector, the primary phase was less and finer without an evident transition region in front of the interface. However, when the two directions were opposite to each other, more and coarser primary phase was obtained with an evident transition region appearing in front of the interface.
1998, 47 (9): 1579-1584. doi: 10.7498/aps.47.1579
We report here a diode pumped Nd∶YVO4 laser emitting at 1342 and 671nm.A maximum output power of 1.75W at 1342nm was obtained under an incident pump power of 5.45W,with an optical-to-optical conversion efficiency of up to 32.1%.With a type Ⅰ noncritically phase-matched LBO crystal as the intracavity frequency doubler,over 500mW of 671nm light was obtained at 6W of incident pump power,the optical-optical conversion efficiency being 8.3%.The output power fluctuates less than 5% while the temperature change of the LBO crystal oven was maintained ±0.5℃ at the phase-matched temperature.