Vol. 54, No. 6 (2005)
Solution of the Kirchhoff equation for thin elastic rod under bending by constraint violation correction method
2005, 54 (6): 2457-2462. doi: 10.7498/aps.54.2457
To further study the mechanical property of a thin elastic rod, this paper will employ the Kichhoff equation which takes the form of Euler quaternion and study the topological configuration of the rod under compression. Adding the constraint condition to the differential equation, we can get a differential-algebraic equation(DAE).In order to be solved easily, DAE will be transformed into a c riterion form. To satisfy the boundary condition, we apply the shooting techniq ue to get the solution satisfying the boundary condition, and imitate the proced ure of pulling and pressing of thin elastic rod suffering a force. Simultaneousl y,to deal with the constraint stabilization phenomenon which is caused by errors , and according to the Euler quaternion character, we select a proper correction coefficient to keep the stability of the differential equation.
2005, 54 (6): 2463-2467. doi: 10.7498/aps.54.2463
By using Hermite transformation, the Wick-type generalized stochastic KdV equation is studied. And the new explicit exact solution is shown via the special truncation expansion method and Hermite transformation.
2005, 54 (6): 2468-2473. doi: 10.7498/aps.54.2468
The Routh equation of a nonholonomic system with a nonlinear constraint equation that is expandable to MacLaurin progression on generalized velocity, can be obtained by Lagrangian multiplier method and d'Alembert principle in an ideal constraint condition. Chetaev condition is valid in linear nonholonomic system only, and is eguivalent to Vacco condition. The so-called “Euler condition" can unite Chetaev condition and Vacco condition, can unite d'Alembert principle and Hamilton principle, and can resolve all existing problems in nonlinear nonholonomic system.
2005, 54 (6): 2474-2477. doi: 10.7498/aps.54.2474
The Noether symmetry and Lie symmetry of the Lagrange system subjected to gyroscopic forces are studied. The condition that the system, under gyroscopic forces , can keep its Noether symmetry and Noether conserved quantity is given. And the condition that the system subjected to gyroscopic forces can keep its Lie symme try and Hojman conserved quantity is also given. Finally, two examples are given to illustrate the application of the results.
2005, 54 (6): 2478-2481. doi: 10.7498/aps.54.2478
The effects of mass variation on form invariance and conserved quantity of mechanical systems are studied. The criterion of the form invariance for constant mass and variable mass systems is given.By comparing the two criterion equations, the condition under which the form invariance is kept is obtained. The condition under which two systems possess the same conserved quantity is also given. An e xample is given to illustrate the application of the result.
Application of analytical thermodynamics: relativistic transformation of temperature in equilibrium thermodynamics
2005, 54 (6): 2482-2488. doi: 10.7498/aps.54.2482
Relativistic transformation of temperature in equilibrium thermodynamics can again be studied with a new view point and method of analytical thermodynamics, and the same result of T=1-β2T0 obtained by Planck, Eins tein or de Broglie can again be obtained. In analytical thermodynamics, its characteristic or adva ntage is that the disputed relativistic transformation δQ=1-β2 δQ0 and the obvious relativistic transformation p=p0 are not needed, they are by-products in the derivation.
A new conservation theorem is studied, the conserved quantity is only constructe d in terms of the infinitesimal generators τ(t,q,q·) and ξs( t,q,q· ) of Lie symmetry of the dynamical equations. Three special cases are discussed, where the Hojman conserved quantity can be deduced as a corollary of this gener al conservation theorem at τ(t,q,q·)=0, and the Lutzky conserved quantity can be derived by using this general conservation theorem at τ=τ(t,q) and ξs=ξs(t,q).Moreover, a condition is presented to exc lude trivial conse rved quantities. Finally, two examples to illustrate the application of the resu lts are given.
2005, 54 (6): 2494-2504. doi: 10.7498/aps.54.2494
The puzzle on the relation between principle of special relativity and cosmologi cal principle, as well as the Beltrami-de Sitter-Lu puzzle on de Sitter/anti-de Sitter spacetimes in Einstein's framework of relativity are analyzed. It i s possible to generalize the principle of special relativity to the spacetimes w ith constant curvature and to establish the kinematics and particle dynamics for the special relativity in de Sitter/anti-de Sitter spacetimes with Beltrami met ric. In such a Beltrami system by the Beltrami coordinate simultaneity is just a n inertial system, the corresponding observers are inertial observers, the inert ial law is valid for test particles and light signals, and observables can be we ll defined which conserve and satisfy the generalized Einstein's formula. In addition to the Beltrami coordinate simultaneity there is also the proper-time simultaneity for the comoving observations and thus the Beltrami metric is trans formed into the Robertson-Walker-like metric which gives a closed 3-dimensional space and its deviation from flatness is of the order of cosmological constant. Therefore, it turns out that in such a kind of special relativity the relativity principle has an intrinsic affiliation with the “perfect” cosmological princi ple and without any puzzle. Furthermore, based on the recent astronomical observ ations, the Mach's principle is restated and it is showed that the cosmologi cal constant acts just as an origin of inertial motions in the de Sitter-invaria nt special relativity on Beltrami-de Sitter spacetime.
2005, 54 (6): 2505-2509. doi: 10.7498/aps.54.2505
A new method, that is, trial equation method, was given to obtain the exact trav eling wave solutions for nonlinear evolution equations. As an example, a class o f fifth-order nonlinear evolution equations was discussed. Its exact traveling w ave solutions, which included rational form solutions, solitary wave solutions, triangle function periodic solutions, polynomial type Jacobian elliptic function periodic solutions and fractional type Jacobian elliptic function periodic solu tions, were given.
2005, 54 (6): 2510-2513. doi: 10.7498/aps.54.2510
The shock wave problems for a class of the nonlinear singularly perturbed equations is studied. Using indirect matching method, the shock solutions of shock wave in an interval are constructed.
2005, 54 (6): 2514-2519. doi: 10.7498/aps.54.2514
The projective Riccati equations method is extended and applied to find new exac t solutions to the Whitham-Broer-Kaup(WBK) equation with the aid of symbolic com putation system Maple.
2005, 54 (6): 2520-2523. doi: 10.7498/aps.54.2520
For a three-dimensional non-harmonic oscillator potential 12r2+A2r 2, the s-wave bound solutions of both Dirac equation and Klein-Gordon equation are giv en when the scalar potential is equal to the vector potential. We find that the radial component equations for both two-dimensional Dirac equation and three-dimensional one are the same when the scalar potential equals to the vector potenti al, and the corresponding s-wave bound solutions for the two-dimensional system are also obtained.
2005, 54 (6): 2524-2527. doi: 10.7498/aps.54.2524
The bound state solutions of the Klein_Gordon equation are obtained.When Hartman n_type scalar and vector potentials are equal. It is shown that the radial and a ngular wave functions are respectively expressed by confluent hypergeogetric an d hypergeogetric functions. In addition, two kinds of recursion relations of ra dial wave functions for given ‘principal' and ‘angular-momentum' quantum numb ers are also derived.
Analytical solutions of the three-dimensional Schr?dinger equation with an exponentially changing effective mass
2005, 54 (6): 2528-2533. doi: 10.7498/aps.54.2528
For an effective mass distribution that is an exponential function of the radial coordinate, the analytical solutions of the three-dimensional Schrdinger equ ation are obtained by using the coordinate transformation method for the referen ce problems with Coulomb potential, Kratzer potential and spherically square pot ential well of infinite depth, respectively. The explicit analytical expressions for the energy eigenvalues and the corresponding eigenfunctions of the three sy stems are presented.
2005, 54 (6): 2534-2539. doi: 10.7498/aps.54.2534
A method that can generate all kinds of nonorthogonal polarization states is induced for long distance and high bit rate generation quantum key distribution. T he polarization states are synthesized by two linearly polarization states contr olled by phase modulator. The modulator is allowed to produced non-quarter_wave phase delay so that can compensate the influence of birefrmgence during transmis sion throuogh the fiber. The structures of the encoder and the decoder based on the method are also described that can effectively reduce the bit error rate.
2005, 54 (6): 2540-2544. doi: 10.7498/aps.54.2540
For tunnel systems in carbon fiber_reinforced concrete, the train of thoughts of approximate calculation using the variational method is precented. And approxim ate Hamitonian quantity of the tunnel system by Lwdin transform is obtained.Th en the tunnel current through the potential barrier is deduced.
Quantization of non-integrable Hamiltonian by periodic orbits: an example of the study on chaotic Henon-Heiles system
2005, 54 (6): 2545-2551. doi: 10.7498/aps.54.2545
Action integrals of the periodic orbits of non-integrable (chaotic) two-dimensio nal system of Henon-Heiles were analyzed to show simple linear relations. This e nables us to obtain by extrapolation all the action integrals of any periodic or bits and at any energies from very few arbitrary action integrals. Based on this property, a very simple and easy semiclassical quantization algorithm by numeri cal arithmetics was proposed for low_energy excitations which are classically ch aotic. The result is good agreement with that obtained by the exact quantal met hod.
2005, 54 (6): 2552-2556. doi: 10.7498/aps.54.2552
The dynamic and statistical properties of several hard balls restricted in a box are studied.The collision distribution in configuration space is main object of the research. Numerical simulations indicate that the distribution function is uniform (horizontal line) when the radius of balls is very small. This uniform p art decreases with increasing size of the balls, and a double-peak distribution is found when the radius exceeds a critical value. Brownian motion is simulated by using hard-ball systems. It can be found that the mean square displacement is proportional to the square of time, i.e., the transport process is dominated by ballistic transport, rather than a diffusion behavior.
On double-peak probability density functions of a Duffing oscillator under narrow-band random excitations
2005, 54 (6): 2557-2561. doi: 10.7498/aps.54.2557
The principal resonance of Duffing oscillator under the narrow-band random exter nal excitation is investigated. The method of multiple scales is used to determi ne the equations of modulation of amplitude and phase. The one-peak probability density function of each of the two stable stationary solutions is then calculat ed by perturbation analysis in the resonant case. These two functions are combin ed by using the probability of realization of the two stable stationary solutions to calculate the double_peak probability density function approximately. Theor etical analyses are verified by numerical results.
2005, 54 (6): 2562-2567. doi: 10.7498/aps.54.2562
Stochastic resonance (SR) in an overdamped linear system with periodically modul ated noise is studied. The explicit expressions of the first two moments and sig nal-to-noise ratio (SNR) are obtained when we introduce the asymmetric dichotomo us noises to the system. Through analyzing the SNR, we find the bona fide SR and conventional SR. Meanwhile, the effects of the asymmetry and correlation time o f the multiplicative noise and cross_correlated noise intensity on the SNR are d iscussed.
2005, 54 (6): 2568-2573. doi: 10.7498/aps.54.2568
A chaotic time series forecasting method based on online least squares support vector machine (LS-SVM) regression is proposed. The difference between the online LS-SVM and offline support vector machine (SVM) is that the online LS-SVM is still effective for the chaotic system with a variation of the system parameter. Four chaotic time series, namely, Chen's system, Rssler system, Hénon map an d chaotic electroencephalogram (EEG) signal, are used to evaluate the performanc e. The results verify the ability of the method in chaotic time series predictio n.
2005, 54 (6): 2574-2579. doi: 10.7498/aps.54.2574
In this paper, a robust finite time fast sliding mode controller is presented fo r a class of chaotic synchronization. Using the fast sliding mode controller, ma ny chaotic systems can achieve synchronization with identical response system th rough state transformation, and Chen's system and hyperchaos system of 4th_order cellular neural network are used to demonstrate the obtained results. The resul ts show that the controller possesses the advantage of fast response and robustn ess.
2005, 54 (6): 2580-2583. doi: 10.7498/aps.54.2580
Synchronization of a new chaotic system called Liu chaotic system is studied.Based on Lyapunov stabilization theorem and nonlinear feedback control method,the sufficient conditions and range of the controller's parameter for self_synchronization of Liu chaotic systems are derived.By combining the parameter adaptive control method and the nonlinear feedback control method,the synchronization of Liu system at speed with unified chaotic systems is implemented.Simulation results validate the proposed synchronization methode.
Sliding mode control for the synchronization of master-slave chaotic systems with sector nonlinear input
2005, 54 (6): 2584-2589. doi: 10.7498/aps.54.2584
This paper analyses the synchronization control for a class of master_slave chaotic systems with parameter uncertainties,external noise disturbances and sector nonlinear input.It designs a class of sliding mode controllers for chaos synchro nization,testifying theoretically that the effectiveness of the controller is be yond the impact from the parameter uncertainties and external noise disturbances of the system under control and thus it is of strong robust nature.Finally,the effectiveness of this kind of controller is also proved by numerical simulations for the master_slave Duffing_Holmes systems.
2005, 54 (6): 2590-2594. doi: 10.7498/aps.54.2590
Using the boundary layer function, we study the stochastic dynamics model on ENS O event. The n-order asymptotic expansion of solution for the original probl em is obtained. By appling the result to a special ENSO event, the zero-order a symptotic expansion is obtained. A theoretical basis for analyzing the behavior of ENSO event is presented.
2005, 54 (6): 2595-2599. doi: 10.7498/aps.54.2595
Based on the single lane traffic cellular automaton(CA) model introduced by Nagel and Schreckenberg(called NS model), Xue Yu et al proposed an improved single lane traffic CA model by considering the relative motion of vehicles(called i mproved NS model).Several faults in the improved NS model using two examples is pointed out and also another single lane traffic CA model by introducing vehicle _moving_status variable and feedback rule is proposed. These methods help to pre vent vehicle from moving backward and stopping hurry. Numerical simulations are carried out and the results indicate that the deceleration probability and traff ic density have a heavy impact on the evolution process of traffic flow. Under t he condition of high deceleration probability, there may happen local traffic ja ms even with low traffic density. And with a constant deceleration probability, the global free phases and jam phases will appear alternately as the traffic den sity increases to a certain level. The phenomenon is very similar to the propaga tion of wave. The traffic flow is higher in the new model than in the improved N S model. This proves that the stop status of the whole traffic flow has been imp roved.
2005, 54 (6): 2600-2605. doi: 10.7498/aps.54.2600
According to the experimental results of Au atomic aggregaties on molten glass surfaces with impurities, based on the characteristic assumption that clusters diffuse with random diffusion steps and rigid rotation angles, an improved restri cted cluster_cluster aggregation model for nonlattice substrates with impurities is established. Then the whole diffusion，rotation and aggregation processes of the clusters are simulated. The impurities are distributed on the nonlattice su bstrate ramdomly, and its influence on the properties of the ramified aggregates is studied systematically .The simulation data are in good agreement with the e xperimental results.
A new method based on the construction of hypothetical symmetrical networks for fixture calibration in network analyzers
2005, 54 (6): 2606-2610. doi: 10.7498/aps.54.2606
At least three known standards are normally required for the full two-port test fixture calibration in vector network analyzers (VNA). In this paper, a calibration procedure using only one standard, based on establishing two hypothetical symmetrical fixtures using triple-through method, is shown. The results using th e calibrating method to subtract the influence of fixtures are in accord with th e directly measured data of the device-under-test (DUT) without the fixtures ver y well, which shows that the proposed method is very simple and accurate.
THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
The property of fractional spin of O(3) non-linear sigma model with non-Abel Chern-Simons term at the quantum level is studied. This formulation is differen t from the classical theories. According to the rule of path integral quantizati on for a constrained Hamiltonian system in Faddeev-Senjanovic scheme，the system is quantized. Based on the quantal Noether theorem，the quantal conserved angu lar momentum is obtained and the fractional spin at the quantum level of this sy stem is presented.
ATOMIC AND MOLECULAR PHYSICS
2005, 54 (6): 2614-2619. doi: 10.7498/aps.54.2614
The energy levels of magnesium_like ion Cu ⅩⅧ in n=3complex configurations are computed by multi_configuration Hartree_Fock with relativistic corrections (HFR) method.The Slater parameters are optimized with the least_square_fit(LSF) technique based on the available experimental data.With these new parameters, th e wavelengths,oscillator strengths and transition probabilities for transitions 3s2—3s3p,3s3p—3p2,3p2—3p3d,3s3d—3p3d,3p3d— 3d2 in n=3complex configurations for magnesium_like Cu Ⅹ Ⅷ are predicted.
Variational calculations and relativistic corrections to the nonrelativistic ground energies of the helium atom and the helium-like ions
2005, 54 (6): 2620-2624. doi: 10.7498/aps.54.2620
Mathematica language is used to make a program that can solve the three_body pro blem with variational method. Considering the nuclear motion, the nonrelativisti c ground energies and the analytic wave functions of the helium atom and the hel ium_like ions (H+, He, Li+, Be++, B3+, C4+, N5+, O6+) are presented by using a simp le effective variational wave funct ion with a flexible parameter k. Based on these results, the influence of a finite nucleus charge radius, the relativistic and radiative corrections on the nonrelativistic Hamiltonian are discussed. The high precision values of the heli um atom and the helium_like ions ground energies are evaluated.
The Dirac_Slater method is used to calculate the photoionization cross sections of Bi79+ from low to high energy. The numerical results are compared with those calculated by the quasi_classical Kramers formula, and the validity of Kra mers formula is analyzed. The relativistic effects and multipole contributions o f the photoionization processes are also discussed. For the comparison with the merged_beam rate coefficients, the theoretical rate coefficients were evaluated with the experimental electron_velocity distribution function(characterized by t he temperatures) parallel and perpendicular to the electron_beam direction. Thou gh the effects of relativity are considered in the present work, the measured ra te coefficients exceed our results in the energy range close to the threshold.
2005, 54 (6): 2633-2637. doi: 10.7498/aps.54.2633
Self_modulation may appear on an intense relativistic electron beam(IREB) trave rsing a two_cavity klystron system. It is caused by the intense relativistic eff ect. RF output can be obtained without RF input. Based on this mechanism, a new type of high_power microwave source is suggested. The oscillation condition of t he intense relativistic election beam, traverse mechanism and PIC simulation are presented. After optimization design, a 800MW output peak microwave power was o bserved at a frequency of 099GHz, while an electron beam of voltage 500kV, cur rent 4kA is injected. The efficiency is about 40%.
2005, 54 (6): 2638-2644. doi: 10.7498/aps.54.2638
The attosecond x_ray pulse trains emitted by a single electron intersecting with an intense Gaussian laser beam have been investigated theoretically and numeric ally by use of Thomson scattering of free electrons. The temporal and spatial ch aracteristics of the radiation are presented for different laser amplitude param eters a0 (1—10) and initial energies of the electron γ0(1 —100MeV). It is found that the durations of the pulse trains and individual pul se depend significantly upon the laser beam width and intensity, as well as the electron energy. Specifically, the individual pulse duration, the separation bet ween neighboring pulses, and the duration of the pulse profile are all proportio nal to 1/γ20. The emission power and energy are propo rtional to γ 60 and γ40, respectively. Whe n changing the laser amplitude a 0，the radiation power is proportional to a20, the individu al pulse duration to 1/a0, and the separation between pulses to a0. When keeping the laser amplitude while changing the beam w idth w0，the number of pulses in the profile, the duration of t he pulse profile, an d the emission energy are proportional to w0. If the laser powe r is fi xed while changing the beam width and intensity, the emission energy and profile duration of the emission pulse train are almost fixed. For a given laser amplit ude a0=1, a beam width w0 equal to 2 laser w avelengths, an d the initial electron energy of 10MeV，for example, the radiation profile of th e pulse trains has a duration of 14×10-3τ0, whic h is only a few attoseconds if the laser oscillation period τ0 is a few f emotoseconds.
Analysis of atom focusing for nanostructure fabrication with a completely off-resonant optical standing wave
2005, 54 (6): 2645-2652. doi: 10.7498/aps.54.2645
The focusing of a thermal atomic beam to nanometer_scale dimensions can be rea lized by a completely off_resonant standing_wave laser field, which can decrease the difficulty of atom lithography experiments. The effects of atom source on a tom focusing are analyzed using the Monte_Carlo scheme and trajectory tracing me thod, and the simulation results have shown that the effective size of the targe t has a much more important effect on feature width than beam spread and longitu dinal velocity spread. Several methods for improving experiments are presented.
A new method for directly measuring frequency and intensity temporal profiles of attosecond XUV pulse simultaneously and completely
2005, 54 (6): 2653-2661. doi: 10.7498/aps.54.2653
A new method of phase determination is presented to measure the frequency and intensity temporal profiles of attosecond XUV pulses directly, simultaneously and completely. Using a cross correlation between femtosecond laser and attosecond X UV, such profiles can be reconstructed from photoelectron energy spectra measure d with two different laser intensities at 0° and 180° with respect to the line ar laser polarization. The method has a temporal measurement range from a quarte r to about half of laser oscillation period. The temporal resolution depends on the jitter and control precision of the laser and XUV pulses. The method can be used for ultra_fast measurement on attosecond time scale.
2005, 54 (6): 2662-2668. doi: 10.7498/aps.54.2662
The one_photon and two_photon absorption properties of a series of 1，4_di methoxy_2，5_divinyl_benzene derivatives are investigated by use of the analytic response theory at HF level. The one_photon and two_photon fluorescence spectra of E，E_2_5_Bis［4′_(N,N_di_n_butylamino) styryl］_1，4_dimenthoxybenzene are measured. The numerical results show that these molecules have strong two_photon absorption cross sections. In the visible light region，the maximal one_photon absorption strengths of the molecules occur in the first excited state. Furtherm ore，the maximal two_photon absorption cross sections of the D_π_A typed molecu les still appear in the first state， but for D_π_D typed molecules the second excited state has the maximal two_photon absorption cross_section. The optical properties of the molecules are closely related to the electric property of the donor and acceptor. The symmetrically substituted molecules can not be determi ned to have a larger two_photon absorption cross section than the asyrnmetricall y substituted molecules for such a kind of π_center. The charge_transfer proce ss for the charge_transfer states is displayed，and then the mechanism of photop olymerization is discussed qualitatively.
Direct measurement of the temporal structure of narrow bandwidth femtosecond XUV using ultra-short laser via differential photoelectron energy spectrum
2005, 54 (6): 2669-2675. doi: 10.7498/aps.54.2669
A method is introduced to directly measure the temporal structure of femtosecond XUV which has a narrow bandwidth using sub_picosecond duration laser. Calculati on shows that such a temporal structure can be reconstructed from the differenti al photoelectron energy spectrum excited by XUV or x ray, modulated by a laser field and measured at 90° or 0° with respect to the linear laser polarizatio n. The effectiveness and nonlinearity of the method are investigated. Energy res olution and bin(s) are important parameters for measurement and calculation. The method has a broad temporal measurement range and can be used for researches of dynamic processes associated with atomic motions.
CLASSICAL AREA OF PHENOMENOLOGY
2005, 54 (6): 2676-2679. doi: 10.7498/aps.54.2676
By using a generalized Lorenz_Mie theory, the scattering field of spheres under Gaussian beams and plane_wave illumination is computed. The code is written with Matlab, and computational methods are improved. Computations for scattered fiel d in our code are extended to fairly large size parameters, up to 80000 The l ight scattering properties of absorbing and nonabsorbing homogeneous spherical p articles, coated spheres are investigated.
Comparison of Lorentz pulsed beams obtained by using complex amplitude envelope representation and complex analytic signal representation
2005, 54 (6): 2680-2685. doi: 10.7498/aps.54.2680
By using complex amplitude envelope representation and complex analytic signal r epresentation, propagation expressions of Lorentz pulsed beams are derived. Prop agation properties of them with different bandwidths are illustrated by numerica l calculations. It is found that they are the same in the neighbourhood of z _axis for narrowband pulses, but in the case of broadband pulses, singularities emerge near z_axis for pulsed beams obtained by using complex amplitude enve lope representation and only complex analytic signal representation is applicabl e. The conditions to decide what representation should be chosen to study pulsed beams are given. And the origin that results in the emergence of singularity is given.
Cross-phase modulational sideband instability in wavelength-division-multiplexing system with periodic lumped amplifiers
2005, 54 (6): 2686-2693. doi: 10.7498/aps.54.2686
Periodically spaced amplifiers along a transoceanic fiber links provide the phas e_matching condition for four_wave_mixing because of Kerr nonlinearity. Both ana lytic method and numerical method are used to study the cross_phase modulational sideband instability in fiber links with periodical lump amplifiers. In the ana lytic method, the gain of sideband instability is obtained. In the numerical met hod, by use of split_step Fourier transform method, the frequency spectra of out put optical pulses are obtained in normal and anomalous fiber links, and there a re sidebands in the spectrum configuration. By comparison of the results from tw o the methods, they are constant with each other.
Monte Carlo simulation for diffuse backscattering of polarized light from poly-disperse highly dense media
2005, 54 (6): 2694-2698. doi: 10.7498/aps.54.2694
A Monte Carlo simulation model for the diffuse backscattering of the polarized l ight from the poly_disperse highly dense media is developed and the effective fr ee pathlength distribution function of the poly_disperse system is given. Simula tion is conducted for the mono_disperse polystyrene suspensions with particle si zes of radii 50 and 550nm, and poly_disperse suspensions containing the above tw o particles with the volume fraction ratios of 4:1, 1:1 and 1:4 The relation b etween the spatial intensity variations of the light diffuse backscattering patt ern and the volume fraction ratio of the poly_disperse suspensions is analyzed q ualitatively.
Experimental study on polarization holographic high density optical data storage with bacteriorhodopsin film
2005, 54 (6): 2699-2703. doi: 10.7498/aps.54.2699
Genetic mutant bacteriorhodopsin BR_D96N film was experimentally studied on its holographic storage properties with different polarization recording waves. The influences of the different polarization states of the recording and readout wav es on the retrieval diffractive image's intensity and signal_to_noise_ratio were compared with each other. The experimental results showed that compared with ot her polarization holographic recording, orthogonal circular polarization recordi ng can realize the separation of the polarization state of the diffractive wave from the scattering noise, and thus has high signal_to_noise_ratio as well as hi gh diffraction efficiency. Using He_Ne laser (633nm, 3mW) as recording and reado ut beam, spatial light modulator as data input element and CCD as data capture e lement, orthogonal circular polarization holographic optical data storage was ma de on 60μm×42μm area of the BR_D96N film by Fourier transform holographic met hod. The area density of 2×108bit/cm2 was obtained, and t he encoded data was retrieved without errors.
2005, 54 (6): 2704-2709. doi: 10.7498/aps.54.2704
By using the definition of Wigner function in Fock states representation，Wigner functions for the photon_added and photon_depleted even and odd coherent states is reconstvucted. The results show that photon_added even and odd coherent stat es always demonstrate non_classical characteristics but photon_depleted even and odd coherent states demonstrate non_classical characteristics only when k t ake odd and even number respectively.
2005, 54 (6): 2710-2716. doi: 10.7498/aps.54.2710
The experimental demonstration of quantum teleportation for continuous variables using the squeezed_state entanglement generated by a type II phase matching opt ical parametric amplifier(OPA) is reported. Type II OPA operating at deamplification can generate amplitude_anticorrelated and phase_correlated entanglements, which can be used in quantum teleportation scheme by direct Bell_ state measurement. The correlation of 2dB was obtained with a pair of KTP crystals in the cavity. The inferred teleportation fidelity is 060,which when correlated for the e fficiency of detection by the output observer, gives a fidelity of 057 The i mperfect factors in detection are also discussed.
2005, 54 (6): 2717-2722. doi: 10.7498/aps.54.2717
Quantum entanglement swapping, i.e. the teleportation of entanglement state, i s a basic method used for developing quantum communication and quantum informati on network. It is necessary to produce two independent entangled states for impl ementing the quantum entanglement swapping. To experimentally demonstrate the en tanglement swapping of continuous variables, we should firstly generate two elec tron paramagnetic resonance(EPR) entangled states with classical coherence and w ithout any correlation of quantum fluctuation. Using a home_made continuous Nd3+YAP/KTP laser to pump two nondegenarate optical parametric amplifiers with the same configuration, we obtained a pair of independent EPR entangled states with classical coherence. The experimental technology of generating two sets of EPR beams is introduced and the influence of mode match on the detection of quan tum correlation is discussed.
2005, 54 (6): 2723-2730. doi: 10.7498/aps.54.2723
A new analytical solution for the phase_mismatched Fokker_Planck equation of deg enerate parametric amplification, and its application in evaluation of the ampli tude quantum fluctuation after passing through the quasi_phase_matching(QPM) dev ice is presented. The calculated results for QPM device, agree with that of the Langevin equation in the case of no loss k=0, and give a general solution fo r k≠0, from which we can derive the influence of squeezing on the loss coef ficient k.
2005, 54 (6): 2731-2734. doi: 10.7498/aps.54.2731
The laser spike of Ne_like argon at 469nm pumped by capillary discharge is mea sured with x_ray diode. Changing the pressure of Ar gas filled in the ceramic ca pillary and the peak value of the main discharge current, we study the effects o f experimental parameters on lasing time, which is the time of spike after the o nset of the main discharge current. The experimental results show that the soft x_ray laser is produced at the rise_time of the main discharge current which is 65%—75% of the peak at the lasing time. The lasing time can be delayed several ns when the pressure increases from 28Pa to 55Pa or the peak of main discharge c urrent decreases. In addition, there is maximum amplitude of the laser spike abo ut 42Pa.
The Z scan theory of thin optically nonlinear medium, by using the fast Hank el transform,is analyzed. The characteristics of Z scan curves under near to p-hat beams are discussed. Meanwhile, the influence of the ratio (diaphragm-gird ling ratio) of the limiting diaphragm radius to the radius of expanded beams on normalized transmittance using near top-hat beams under closed-aperture is analy zed. Through theoretical analysis, the ratio with the best sensitivity is given. Finally, the influence of the size of the far-field diaphragm on normalized tra nsmittance under the experimental configuration with the best sensitivity is ana lyzed.
Dynamical evolution of rigid holographic bright solitons based on photorefractive two-wave mixing with moving grating
2005, 54 (6): 2739-2744. doi: 10.7498/aps.54.2739
It has been investigated that dynamical evolutions of spatial optical solitons i n dissipative photorefractive systems based on two-wave mixing with a moving gra ting. Numerical results show that the stability of rigid photorefractive hologra phic solitons in such systems depends strongly on the system parameters. The sol iton for some sets of system parameters can propagate stably in the crystal over a distance that is long enough. The larger the ratio of the phase to intensity coupling coefficient of two-wave mixing, the better the stability of solitons. P otential application in optical switches, repeaters or splitters is discussed.
Compensation of group velocity mismatch for optical parametric amplification in BBO type-I phase-matched configuration
2005, 54 (6): 2745-2750. doi: 10.7498/aps.54.2745
A method that compensates completely the group velocity mismatch between three w aves for femtosecond optical parametric amplification (OPA) in BBO type-I phase- matched configuration is presented by combining noncollinear configuration with tilting pump wave front. When the group velocities of the three waves are matche d, the variations of the noncollinear angle, the phase-matched angle and the pum p wave front tilt angle with the signal wavelength are calculated theoretically, and the effects of the pump beam size and the spatial walk-off length are analy zed. The results indicate that this method not only can achieve maximal parametr ic bandwidth, but also can match completely the group velocities between three w aves for femtosecond OPA. In addition, with increasing parametric gain, it is ve ry importance to appropriately choose the pump beam size and the nonlinear cryst al length.
Surface plasmon polaritons and its coupling with cavity mode in the system of dielectric spherical shells periodically mounted in a metal substrate
2005, 54 (6): 2751-2757. doi: 10.7498/aps.54.2751
We investigate the surface plasmon polaritons and its coupling with other electromagnetic modes by observing the absorption spectrum on a system of dielectric spherical shells periodically mounted in a metal substrate. We found that there exist two resonance frequencies in the system corresponding to surface plasmon polaritons mode and cavity mode. At these frequencies, we can find related peaks i n absorbance. Since the surface plasmon polaritons cannot couple with the incide nt plane wave directly and both couplings of the cavity mode with the incident w ave and the surface plasmon polaritons are also weak, so the strength of absorpt ion peaks are generally very limited. However, we can adjust some parameters in the system to make the surface plasmon polaritons and the cavity mode with almos t the same frequency. In this case, the coupling can be dramatically enhanced, a nd we can observe very strong peaks in absorbance. The relationships of resonanc e absorption with some physical and geometrical parameters are discussed in deta il.
2005, 54 (6): 2758-2763. doi: 10.7498/aps.54.2758
The temperature and strain sensing property of a grapefruit microstructure fiber (MF) Bragg grating with multi-reflection peaks have been studied. Analysis indicates that the wavelength shift of this grating changes quadratically with the environmental temperature. Experimental results show that different reflection p eaks have their individual temperature sensitivities. Furthermore, the relations hip between the wavelength shifts and temperature variation has been fitted, whi ch confirms the above analysis. However, theoretical analysis indicates that the wavelength shift have a good linear relationship with the strain change. The re lationship between the wavelength shift and strain changes has been fitted throu gh experiment. The inconsistent sensitivity of different reflection peaks for th is grating ensures its practical applications in the field of multi-parameter se nsing measurement.
2005, 54 (6): 2764-2768. doi: 10.7498/aps.54.2764
Laser pulse durations are dominated by the spectral bandwidths in chirped pulse amplification systems.Therefore,gain narrowing during amplification is one of the most important factors that limits the minimal pulse durations of compressed pulses in high_power ultrashort_pulse laser systems.The gain narrowing can be compensated by applying an acousto_optic programmable dispersive filter(AOPDF) to the laser system.Here we present the experiments and results with an AOPDF for the 200_TW Ti:sapphire laser.The spectral bandwidth is increased from the original 27?nm to 44?nm.The pulse duration correspondingly is decreased from 60?fs to 30?fs and thus the output pulse power is doubled.
2005, 54 (6): 2769-2773. doi: 10.7498/aps.54.2769
The spectrum broadening and pulse compression of the ultrashort pulse propagatio n in cascaded hollow fibers,by solving the generalized nonlinear Schrdinger eq uation with the split_step Fourier Method,are discussed.The simulation shows tha t the technique using cascaded hollow fibers is a reliable route to achieve few to mono-cycle pulses of high energy.
2005, 54 (6): 2774-2778. doi: 10.7498/aps.54.2774
Using the degree of polarization as feedback signal to detect the polarization m ode dispersion (PMD) variation in the fiber links, an experiment of dynamic adap tive PMD compensation in 4×10?Gb/s optical time-division multiplexed (OTDM) tr ansmission system is reported. The PMD compensator consists of a polarization co ntroller and a variable delay line with four degrees of freedom. Based on the va riable step-size peek search algorithm, the performance of the PMD compensator i s assessed in the eye pattern of a received signal. It is shown that the maximum compensated differential group delay is 25?ps, i.e. one bit period, and the co mpensation time can be less than 50?ms.
2005, 54 (6): 2779-2783. doi: 10.7498/aps.54.2779
The multi-scale wavelet decomposition and orthogonal wavelet transform are outli ned and applied to the representation of optical pulses. The nonlinear Schrdin ger(NSL) equation, which describes the pulse propagation in optical media, is us ed to represent the split-step operator form in wavelet domain. The iterative eq uation of the split-step wavelet algorithm for the solution of the NLS equation is presented. The expression of the linear operator in wavelet domain is given a nd the framework of the derivative operator is discussed. As an example, the linear and nonlinear propagations of ultrashort Gaussian pulse through optical fibers are numerically simulated by using the split-step wavelet method (SSWM), and compared with that by using the analytic solution and the split-step Fourier met hod. The results show that SSWM is an accurate and effective numerical method fo r the study of the pulses propagation through optical media.
This paper shows that for a static cohesionless granular material simply averaging in space the strains inside grains does not result in its macroscopic strain , so the fields of displacement vector and strain tensor do not have the propert y of coarse-graining. However this gives no disturbance to the validity of the n otions of strain and elasticity for the granular material because they are based on the equilibrium thermodynamics.
2005, 54 (6): 2791-2798. doi: 10.7498/aps.54.2791
The evolution of micro-voids under dynamic loading mainly contributes to the dynamic damage of ductile materials. In this work, the evolution of a preexisting nano-void in single crystal copper is investigated by means of molecular dynamics(MD) simulation. The relation between the time evolution of complicated stress distribution and the void growth is obtained. The precompression process before the tension process has strong influence to the void growth. That high threshold makes the void grow coincides with the trend that a shorter tension duration wi ll lead to a higher spallation strength, which was found in latest single crysta l spallation experiment.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
2005, 54 (6): 2799-2803. doi: 10.7498/aps.54.2799
Robust control of atomic coherence and population transfer among Zeeman sublevel s in the ground states of atom is investigated theoretically using adiabatic rap id passage on a nanosecond time scale. It is shown that a slight change in the p ump pulse time delay relative to the Stokes pulse leads to a significant modific ation of atomic coherence and population transfer. This coherence control of qua ntum state and population is presented by numerical simulations based on self-co nsistent set of density matrix equations and Maxwell equations.
Plasma photonic crystals are artificially periodic structures, which are compose d of plasmas and dielectric structures (or vacuum). In this paper, the piecewise linear current density recursive convolution (PLCDRC) finite-difference time-do main (FDTD) method is applied to study the plasma photonic crystals and those co ntaining defects. In time-domain, the electromagnetic(EM) propagation process an d reflection/transmission electric field of Gauss pulses passing through the pla sma photonic crystals are investigated. In frequency-domain, the reflection and transmission coefficients of the pulses through the two kinds of crystals are co mputed. The results illustrate that the plasma photonic crystals mostly reflect for the EM wave of frequencies less than the plasma frequency, and mostly transm it for EM wave of frequencies higher than the plasma frequency. In high frequenc y domain, the plasma photonic crystals have photonic band gaps, which is analogo us to the conventional photonic crystals.
2005, 54 (6): 2809-2813. doi: 10.7498/aps.54.2809
A preliminary experiment for triggering a plasma current quench by means of injection of high_Z impurities has been performed on the HL_1M before the major disruption.Using injection of impurity with higher charge of the nuclei allows u s to increase the radiation cooling on a 3?ms time scale and the electronic tem perature loss contract is 80% before current terminates.It can be a simple and p otential approach to decrease significantly the plasma thermal energy and the ma gnetic field energy before a disruption and to a safe plasma termination.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
2005, 54 (6): 2814-2820. doi: 10.7498/aps.54.2814
The properties of silica sol, such as the interface characteristics and microstr ucture, were comparatively studied by small angle x-ray scattering (SAXS) assis ted by dynamic light scattering. Four synthesis routes were adopted to relate th e properties of silica sol with the synthesis situation. Very big difference of SAXS results was found between the base-catalyzed and the acid-catalyzed silic a sols with ethanol used as solvent. Under the acid-catalysis of low molecule-w eight organic acid, not only were polysiloxane macromolecules obtained, particle suspension of silica was also produced with complicated inner structures of pa rticles. With ethanol or water as solvent, it was found that the silica particl e would become more irregular in morphology with more polarity of solvent. The formation of Si-O tetrahedron was more difficult in the acidolysis of tetraetho xysilane by formic acid than in the other hydrolysis routes. An interesting co- existing of positive deviation and negative deviation from Porod’s law was foun d in the silica sol with water solvent, and a detailed explanation has been giv en.Many nano-scaled structural difference among these different synthesis situa tions were revealed, which was difficult to be recognized by the experimental m ethods other than SAXS.
2005, 54 (6): 2821-2825. doi: 10.7498/aps.54.2821
Small_angle neutron scattering technique is employed to investigate the structure of fullerene-PVP polymers and the variation of their size with fullerene content. The results indicate that the relative lengths of both mono-molecule and mac romolecule chains in solution with fullerene are shorter than those in pure PVP solution, and the volumes of fullerene-PVP polymers in solution with high fullerene content become much smaller.
Molecular dynamics simulation for thermophysical parameters of sodium chloride solids at high temperature and high pressure
2005, 54 (6): 2826-2831. doi: 10.7498/aps.54.2826
By means of molecular dynamics simulation and the effective optimized two_body Tosi-Fumi potential, the isothermal compression curve and thermophysical parameters of sodium chloride solids in the temperature range 298—1073?K are calculat ed.The result demonstrates that the Gruneisen parameter of sodium chloride γ= γ0(V/V0)q is approximately correct in the te mperature range 298—1073? K and the pressure range 0—80?GPa,and the exponent q in the formula is abo ut 1078.
2005, 54 (6): 2832-2837. doi: 10.7498/aps.54.2832
Molecular dynamics simulation of nanoparticle colliding with monocrystalline silicon surface has been carried out in order to investigate the repulsion behavior of nanoparticles. The dynamical behavior of the nanoparticle, the atomistic structure of elastic and plastic deformation of the substrate, and the transformati on of energy during the collision process are analyzed. A hemispherical crater i s formed on the Si(001) substrate, and there exists an amorphous layer on the wa ll of the crater. In the collision process, the atoms of the substrate that lie near the nanoparticles transform to amorphoustate immediately. And the elastic d eformation which is characterized by the reversible (111)［110］ glide structure is produced outside the amorphous layer. During the incidence stage, the substr ate undergoes compressed elastic deformation. And during the repulsion stage, th e potential energy of the substrate declines oscillatory with compressed elastic deformation and tensed elastic deformation formed alternately. The compressed e lastic deformation energy stored in the substrate is transferred to the transnat ional kinetic energy of the nanoparticle, which forces it back from the surface.
2005, 54 (6): 2838-2842. doi: 10.7498/aps.54.2838
The formation of bulk nanocrystalline alloys based on the Pr60Al 10Ni 10Cu20 bulk metallic glass forming alloy by doping Fe is r eported. B y varying the content of Fe, the microstructure of the Pr-based alloy changes pr ogressively from full glassy state to composite with nanocrystalline particles e mbedded in the glassy matrix, and finally into nano-structured state accompanied by the gradual magnetic property changes. A simple approach to obtain the bulk nanocrystalline material with controllable microstructure is presented, and the relation between microstructure and property is discussed.
2005, 54 (6): 2843-2846. doi: 10.7498/aps.54.2843
La_Sr_Cu_O thin films on Si(100) substrates have been grown by pulsed electron beam deposition technique.The thin films obtained have been characterized by x_ray diffraction (XRD),scanning electron microscope(SEM),energy dispersive x_ray analysis (EDX) and focusing ion beam (FIB) technology.Highly ordered surface nanostructure has been found.FIB technology has been used to characterize those nanostructures.The nanostructure was cut by FIB,and its cross section can be seen clearly also.The nanostructure was etched by FIB step by step,and the depth_resolved morphology was shown.It is suggested that those nanostructures could come from the thermal expansion and lattice mismatching between Si substrate and La_Sr_Cu_O thin film.If the growth of the nanostructure can be controlled,it could be used to form high_Tc junctions by directly growing.
2005, 54 (6): 2847-2852. doi: 10.7498/aps.54.2847
A tentative plan to prepare new clusters by self-assembly of C36 clusters in gas-phase is given in this paper. The growth process of the carbon clusters under a real He atmosphere is simulated by molecular dynamics method. We find that the ambient temperature is the key factor to affect the final structures of the n ew clusters: from 1000 to 2000 K, the new clusters keep a pod shape after self-assembly of C36 clusters; and above 2000 K, the structures of the final clusters change into a ball shape.
2005, 54 (6): 2853-2858. doi: 10.7498/aps.54.2853
Diamond thin films of different structures were prepared by using chemical vapor deposition on WC(6%Co) substrates under different conditions.Reman spectroscopy was used for the quality evaluation of the diamond films.The cracking size in indentation tests was used for the evaluation of adhesion strength,and the influence of structure of diamond films on the adhesion was studied.Results obtained show that: (1) The buffer role of sp2_carbon between grain boundaries greatly affect the residual stress of the film,hence the cracking size decreases steadily with increasing sp2 content.(2) The increase of nucleation density is mainlyh due to the contribution of the diamond seed grains left. In this case,the increase of nucleation density cannot effectively improve the chemical adhesioe force between the film and the WC substrate,and cannot improve the adhesion between the film and the substrate.(3)For thinner films there is no compressive stress among diamond grains,hence the cracking size does n t increase apparently with increasing deposition time.Strong compressive stress emerges only after the thickness increases to a certain value,and then the cracking size increases rapidly with increasing deposition time.
2005, 54 (6): 2859-2862. doi: 10.7498/aps.54.2859
C60-PMMA composite films were prepared by the sol-gel method, and the structure, Uv-Vis absorption, Raman scattering, IR absorption of the films were s tudied. The charge-transfer effect was studied between C60 and PMMA by an alyzing their Uv-Vis absorption spectra, Raman scattering spectra, IR absorption spectra.
2005, 54 (6): 2863-2867. doi: 10.7498/aps.54.2863
TiO2 thin films, which were heat-treated with an applied electric fie ld, were prepared by sol-gel method. The phase transformation behavior of TiO2 thin fil ms was studied by differential thermal analysis, atomic force microscopy and Ra man spectroscopy respectively. It was indicated that the phase transformation of non-crystalline to anatase could be accelerated with an applied electric field. Studies on photo-catalytic degradation showed that the photo-catalytic activity of TiO2 thin films in an applied electric field became higher.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
2005, 54 (6): 2868-2872. doi: 10.7498/aps.54.2868
In order to investigate the magnetovolume instability in compound LaFe11.5Si1.5, we employed first-principles electronic-structure calcul ations b y using a full-potential linearized-augmented-plane-wave method within the gener alized-gradient approximation. The total energies of nonmagnetic and ferromagnet ic states were calculated by spin-polarization approach and the calculated resul ts showed that there is little difference between them. The fixed-spin-moment ca lculation confirmed that the metamagnetic transition was associated with low-sp in-high-spin transition in compound LaFe1.5Si1.5. Based o n the ca lculated results, we could explain qualitatively some of the experiment results.
2005, 54 (6): 2873-2876. doi: 10.7498/aps.54.2873
Monte Carle method and embedded-atom potential were utilized to study the energetics and structures of high_temperature copper clusters, which contained 55 ato ms. First, we calculated the energetics and structures of Cu55 at 2 00?K.T he results that we got well accord with those Suleyman Ozcelik et al obtained. I t is shown that this method is reliable. Then, the system was cooled from 12000 ?K, in a step of 1000?K, the energetics and structures were measured while th e system reached equilibrium. At each temperature, the Monte Carlo Stepsare 10 6. From the simulation we found that above 10000?K, the system only contain a few atoms that are combined together and unsteady,so single atoms are getting more. Between 10000 and 6000?K, the structure of the system gradually changes to forming nucleating center, other atoms nucleated with nucleating center; Atta ined equilibrium at 5000?K, the system atom is already complete combinative tog ether without the monatomic, the energy is -11206?eV; Further lower the tempe rature, the system construction becomes from irregular、dissymmetrical to regula r、symmetrical forming a double icosahedral shape, the energy is -16850?eV; W ith visual displaying, a very clear evolving structural diagram was achieved wit h lower in temperature.
Effects of oxygen adsorption on the electronic structure and optical properties of single-wall carbon nanotubes
2005, 54 (6): 2877-2882. doi: 10.7498/aps.54.2877
The binding energy,energy band structure and optical properties of the oxygen physical adsorption on semiconducting single_wall carbon nanotube are studied by the density functional theory. The most stable adsorption site is the one in which the oxygen molecule lies above the center of the carbon ring. It is showed th at the oxygen physical adsorption strongly affects the transport properties and the optical absorption spectra of carbon nanotubes. And the phenomenon of oxygen photoinduced desorption has been explained theoretically.
Investigations of magnetic interactions and spin-Hamiltonian parameters for 4B1(3d3) state ion in a tetragonal crystal field
2005, 54 (6): 2883-2892. doi: 10.7498/aps.54.2883
The magnetic interactions as well as the microscopic origins of the spin_Hamilto nian (SH) parameters including b02, g∥, g⊥,Δg for 4B 1(3d3) state ion in a tetragonal crystal field have been investigated usin g the complete diagonalization method (CDM). It is found that the contribution t o the spin_Hamiltonian parameters arising from the spin_orbit (SO) magnetic inte raction is the most important for most part of the crystal field (CF) ranges. H owever, the contributions to the zero_field split (ZFS) parameter b02 fr om the other three mechanisms including the SS mechanism and SOO mechanism as we ll as SO_SS_SOO combined coupling mechanism exceed 20% for most part of the CF ranges, especially for some CF ranges, in which the contributions to the ZFS pa rameter b02 from the other three mechanisms exceed tha t from the SO mech anism. It is shown in present studies that the approximate expression of ZFS par ameter b02 developed by Macfarlane is not convergent f or most part of t he CF ranges. The microscopic origins of the splitting in the lowest existing st ate 2Eg are studied. Different mechanisms of the splitting 2 Eg state for C4v and C3v crystal fiel ds are explained using group theory.
2005, 54 (6): 2893-2898. doi: 10.7498/aps.54.2893
In order to get more knowledge about the difficulty of conductivity-type inversion in ZnO, this paper performs the thermodynamical analysis of intrinsic point defects. Relations between the main defect concentrations and the environment pa rameters, such as the temperature and oxygen pressure, have been formulated unde r thermodynamical equilibrium. The K-V figure is presented. It is shown that it is very difficult to obtain p-type conductivity under thermodynamical equili brium. Based on these facts, this paper gives the effective approaches to realize p-type conductivity inversion. The feasibility of the analysis is also pro ved by some experiments.
Studies on the strain and its effect on defects in heteroepitaxial ZnO films prepared by LP-OCVD method
2005, 54 (6): 2899-2903. doi: 10.7498/aps.54.2899
High_quality ZnO films have been epitaxially grown on Si substrates by low_pressure metal organic chemical vapor deposition(LP_MOCVD) and two kinds of samples have been prepared:one is ZnO directly grown on Si while the other one grown with a SiC buffer layer.According to the results of Raman spectra,XRD,AFM,and photoluminescence,it is indicated that the tensile strain in the epitaxial ZnO films has a great influence on the crystalline quality of ZnO films,and the SiC buffer layer can effectively modulate the tensile strain,hence reduce the concentration of defects and improve the film quality.Then,from the defect formation mechanism,we suggest that for ZnO/Si,the large tensile strain results in high concentration of non_radiation recombination centers,which largely reduce the intensity of UV and green emissions; but for ZnO/SiC/Si,the small tensile strain results in oxygen antisite defects OZn in ZnO films,which enhance the green emis sion in photoluminescence.
2005, 54 (6): 2904-2909. doi: 10.7498/aps.54.2904
Both the effects of the intermixing induced by the implantation dose and the annealing temperature on the light-emission efficiency of the quantum dots are studied. The intensities of photoluminesce (PL) are determined by the carriers c apture time and non-radiative center lifetime.Annealing can partly eliminate the non-radiative center (NRC), so the NRC generation rate is a sublinear function of the proton dose (N). The carrier capture efficiency enhancement is induce d by intermixing and degradation by the implantation damage which mutually compe te, so there exists a critical implantation dose (NC). When N is less than NC, the intermixing is the main effect and the PL intensity increases with the implantation dose. On the other hand, when N is larger than N C, the implantation damge is so large that the intensity decreases wi th the do se. The higher the annealing temperature, the larger the NC becom es.
2005, 54 (6): 2910-2917. doi: 10.7498/aps.54.2910
The properties of the ground state of a closed dot-ring system with a magnetic flux in the Kondo regime are studied theoretically by means of a one-impurity Anderson Hamiltonian. The Hamiltonian is solved by means of the Slave-Boson mean-field theory. It is shown that at T＝０, a suppressed Kondo effect exists in this system even when the mean level spacing of electrons in the ring is larger than the bulk Kondo temperature; the physical quantities of this system depend sensitively on both the parity of the system and the size of the ring; the rich physical behaviors of this system can attribute to the coexistence of both the f inite-size effect and the Kondo screening effect in this system. It is also poss ible to detect the Kondo screening cloud by measuring the persistent current or the zero_field impurity susceptibility χimp directly in future exp eriments.
2005, 54 (6): 2918-2923. doi: 10.7498/aps.54.2918
High-temperature electrical properties of 4H-SiC n-MOSFET are simulated and anal yzed by considering changes of mobility and threshold voltage with temperature. The simulated results are in good agreement with experimental data. Further mor e, influences of main structural and technological parameters on high-temperatur e electrical properties of devices are discussed for obtaining optimum values o f these parameters.
2005, 54 (6): 2924-2928. doi: 10.7498/aps.54.2924
Using Langevin molecular dynamics method, we have studied the voltage noise spectrum generated by current-driven vortices as a function of the magnetic field an d current. It is found that the broad band noise (BBN) at low frequencies decrea ses with increasing magnetic field, it decreases at the magnetic field near th e vortex dynamic transition field FP， and the Lorentze narrow ba nd noise (NBN) at high frequencies appears. As the magnetic field increases near the melt ing field Fm, the NBN peak goes up and shifts towards higher freq uencies. In the elastic motion region of vortices with strong driving currents, NBN exhib its the washboard-like shape. This behavior arises from the periodic modulation of the translational velocity of vortices, suggesting that there is a Bragg gla ss phase with the translation order in the vortex lattices of the layered superc onductors.
2005, 54 (6): 2929-2933. doi: 10.7498/aps.54.2929
Giant magneto-impedance (GMI) effect of a multilayered film with the structure o f (FM/SiO2)3/Ag/(SiO2/FM)3 (FM≡FeCu CrVSiB) was studied. The multilayere d film was deposited by radio frequency sputtering onto a single crystal Si subs trate. A constant magnetic field of about 72kA/m was applied along the longitudi nal direction of the film plane during deposition process, and then the samples were annealed at different temperatures. Results obtained show that the multila yered film has good soft magnetic properties and GMI effect even though in the a s-deposited state. The maximum magnetoimpedance ratios are about 45% and 44% in longitudinal and transverse cases, respectively. After the samples were annealed at 230℃ for 90min, the best GMI effect could be obtained. The maximum longitud inal and transverse magnetoimpedance ratio up to 251% and 277% were obtained at the frequency of 8.5MHz, respectively. The GMI effect in this multilayered struc ture is much stronger than the one in FeCuCrVSiB/Ag/FeCuCrVSiB sandwiched film w ith the same thickness of total magnetic layers.
2005, 54 (6): 2934-2937. doi: 10.7498/aps.54.2934
Using the solid_state diffusion method, a series of Sn1-xMnxO2(x=002—006) diluted magnetic semiconductors(DMSs) are fabricated.By u sing x_ray diffraction(XRD) measurements and Fouier transform infrared spectrosc opic(NEXUS870) analyses,a uniform Mn distribution in the SnO2 is conf irmed. An obvious ferromagnetism in Mn_doped SnO2 DMS at room temperature is f ound and the ferromagnetism is weak with the increase of Mn concentration.
2005, 54 (6): 2938-2944. doi: 10.7498/aps.54.2938
LaNiO3 (LNO) thin films were successfully prepared on Si (100) and Pt /Ti/SiO 2/Si substrates by metalorganic decomposition (MOD). Pb(Zr0.52Ti0.48)O3（ＰZＴ） thin films were prepared on the Pt( 111)/Ti/SiO2/Si, LNO/Si (100) and LNO/Pt(111)/Ti/SiO2/Si substrates by a modified sol-gel met hod. The crystallographic orientation and the microstructure of the resulting PZT thin f ilms on the different substrates were characterized by x_ray diffraction and sca nning electron microscopy. The dielectric and ferroelectric properties of PZT fi lms on the different substrates are discussed. The PZT films deposited on LNO/Pt /Ti/SiO2/Si and LNO/Si（100） substrates show strong ［100］ preferre d orient ation, while the films deposited on Pt/Ti/SiO2/Si substrates show ［1 10］ ori entations. PZT films on LNO/Pt/Ti/SiO2/Si and LNO/Si(100) substrates have lar ger average grain sizes, dielectric constant and remnant polarizations compared with those grown on Pt/Ti/SiO2/Si substrates.
2005, 54 (6): 2945-2949. doi: 10.7498/aps.54.2945
The successful application of boron_doped hydrogenated nanocrystalline silicon a s window layer in a-Si∶H nip solar cells on stainless steel foil with a thickne ss of 005mm is reported. Open circuit voltage and fill factor of the fabricate d solar cell were 090V and 070 respectively. The optical and structural prop erties of the p-layers have been investigated by using UV-VIS and Raman spectros copy. It is confirmed that the p-layer is hydrogenated nanocrystalline silicon w ith a wide optical gap due to quantum size effect.
INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
Photoluminescence study of (GaAs1－xSbx/InyGa1－yAs)/GaAs bilayer quantum well grown by molecular beam epitaxy
2005, 54 (6): 2950-2954. doi: 10.7498/aps.54.2950
Photoluminescence study of (GaAs1-xSbx/InyG a1-yAs)/GaAs bilayer quantum wells (BQWs) grown by molecular beam epitaxy (MBE) were carried out. Temperature and excitation power dependent photoluminescence (PL) s tudy indicated that the band alignment of the BQWs is type - Ⅱ. The origin of the double-peak luminescence was discussed. Under optimized growth conditions, t he PL emission wavelength from the BQWs has been extend up to 131 μm with a s ingle peak at room temperature.
2005, 54 (6): 2955-2960. doi: 10.7498/aps.54.2955
The effects of DC and AC magnetic fields on the interfacial microstructure betw een molten aluminium and solid iron were studied, and the intermetallics formed in the diffusion layers were also investigated by means of metallography, electr on microprobe (EPM) and x-ray diffraction (XRD). Results showed that the diffusi on layer in solid iron under DC and AC magnetic fields was thinner than that w ithout magnetic field, and the interface became irregular under AC magnetic fiel d. In the direction perpendicular to the magnetic field, DC magnetic field dampe d the diffusion between aluminium and iron; on the contrary, under AC magnetic field diffusion was enhanced; the diffusion layer in solid iron was mainly comp osed of Fe2Al5 and FeAl3 without magnetic field , while there was only Fe2Al5 under DC magnetic field, and Fe2Al5 and Fe4Al13 under AC magn etic field.
GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS
2005, 54 (6): 2961-2968. doi: 10.7498/aps.54.2961
All available V-band optical data on H0323+022 from a good many of references ar e compiled.The long-term light curve in the V_band from 1982 to 2003 for BL Lac object H0323+022 is obtained, and the optical photometry of the sourse,which were observed with the 1 m telescope of Yunnan Astronomical Observatory and 1.56 m telescope of Shanghai Astronomical observatory,is presented.Observed results show significant rapid variation and exhibit short_time variability of 23 min in R band.It is found a strong correlation between the B-V colour index and the mag nitude in the B band. CCD photometry of H0323+022 showed that they are in good a greement with the results of Bai et al (1998).It is possible to estimate a b lack hole of emitting region R from the shortest time scale of H0323+022 object.