Vol. 46, No. 2 (1997)
1997-01-20
GENERAL
1997, 46 (2): 209-226.
doi: 10.7498/aps.46.209
Abstract +
By the method of algebraic dynamics,the exact solutions and Cartan invariant operators of the SU(3) linear nonautonomous quantum system have been obtained,the quantum-classical correspondence of the solutions established.The nonadiabatic Berry phase for a periodic system is also- calculated.
1997, 46 (2): 227-237.
doi: 10.7498/aps.46.227
Abstract +
The Bloch theorem holds also for the evolution of states in the cyclic quantum systems in which the Hamiltonian varies cyclically with time.In light of the theorem a new type of geometric phases——Bloch phases——is defined.In this paper it is shown that the resonant-(i.e.,acquired by certain states after evolving a cycle)geometric phases so far discovered can all be unified into the Bloch phases.That is,the Bloch phases are identical with the Pancharatnam phases,Aharonov-Anandan phases and Lewis-Riesenfeld phases,and reduce to the Berry phases in adiabatic approximation.To this end,the equivalent alternation of defining the former three types of quantum phases and the generalization of Lewis-Riesenfeld phases and Berry phases to the degenerate case are made.In addition,two methods are given for efficiently searching for the Bloch phases.
1997, 46 (2): 238-248.
doi: 10.7498/aps.46.238
Abstract +
Modulation on electromagnetic waves with angle frequency ωe,travelling around a circular waveguide by high-frequency plane gravitational waves with angle frequency ωg,incident perpendicularly to the plane,where the waveguide is located,is discussed.Results present that in the vicinity of symmetric plane,perpendicular to the travelling direction of gravitational waves, of the waveguide,energy flux density of electromagnetic waves,generally will be added by three new components with angle frequencies(2ωe±ωg)and ωg,respectively.In the case as ωg》ωe,ratio-modulation of amplitude of energy flux density is as large as h0, the dimensionless amplitude of the gravitational wave,in order.Specially,when for ωg,ωe and ω0,the cyclical angle frequency of electromagnetic waves around the waveguide, ωg=2ωe》ω0 is satisfied,energy flux density will be greater than h0 in order because of some mechanism,similar to resonance.The results don't vanish when these parameters have a small change.It is very important to detect the very weak signals of gravitational waves.
ATOMIC AND MOLECULAR PHYSICS
1997, 46 (2): 249-254.
doi: 10.7498/aps.46.249
Abstract +
Based on the quantum defect theory, the infinite Rydberg states and its adjacent continue states with the same angular moment property will form a channel. Previous studies have considered the collision-induced transitions from a single initial state to a final channel. Here we extend these thoery to include all possible transitions between two channels. By defining a renormalized generalized oscillator strength density (GOSD) which varies smoothly across threshold, the inelastic collisions from an initial channel to a final channel can be treated in a unified manner. As an example, we present the renormalized GOSD of the Rb atom from s-initial to p-final channel, and also from s-initial to s-final channel.
CLASSICAL AREA OF PHENOMENOLOGY
1997, 46 (2): 255-266.
doi: 10.7498/aps.46.255
Abstract +
Operation in the steady state and squeezing of quantum noise in two-mode two-photon correlated-spontaneous-emission lasers(CEL) are studied via nonliner quantum theory.It is shown that the two-mode two-photon CEL exhibits lasing without inversion and two-mode hysteresis even without triggering.The features of squeezing of quantum noise in the relative amplitude and the average phase are given.
1997, 46 (2): 267-271.
doi: 10.7498/aps.46.267
Abstract +
By solving the 1-dimensional time-dependent schrdinger equation,the ionization probability and harmonic spectra of atom under different laser intensities are obtained,and the relation between the ionization and harmonic emmission is discussed.The result is that under certain range of laser intensity during which the ionization is stable or supperessed,the harmonics will be emitted efficiently.
1997, 46 (2): 272-278.
doi: 10.7498/aps.46.272
Abstract +
A single-particle approach is used to derive the small signal gain for harmonics in the novel wiggler proposed by Pinhas.The results are similar to that in ordinary planar undulator free-electron lasers.
1997, 46 (2): 279-286.
doi: 10.7498/aps.46.279
Abstract +
In this paper,we have computed with three different methods the electron beam energy modulation in optical klystron on storage ring free electron laser and also computed the effects of the electron beam parameters on energy modulation.The numerical results show that the three dimensional simulation is necessary.
1997, 46 (2): 287-292.
doi: 10.7498/aps.46.287
Abstract +
FEL efficiency improvement with magnetic field increasing wiggler has been- investigated.-Numerical simulation with KMR equations considering space charge effect we find that FEL power increase greatly.It is interested that the larger the energy spread is,the greater the FEL power increasement is.Therefore the-whole electron beam of the accelerator can be used for FEL and higher power can be gotten with magnetic field increasing wiggler.
1997, 46 (2): 293-299.
doi: 10.7498/aps.46.293
Abstract +
The electron orbits in Gaussian beam′s laser wiggler are analysed.The single-particle orbits due to large amplitude,backward propagating pump laser field and axial guide magnetic field are derived,and the stabilities of the orbits are discussed.It is found that the results agree with that of the plane electromagnetic wiggler.Similiar to the orbits in magnetostatic wiggler in free-electron laser (FEL),the orbits in pump laser field have two classes of orbits.However,different from the orbits in a magnetostatic wiggler,the two classes of orbits in pump laser are stable.
1997, 46 (2): 300-305.
doi: 10.7498/aps.46.300
Abstract +
Using the output of one dye laser as the fundamental wave,we have generated tunable VUV coherent radiation from 116.6nm through 119.2nm by nonresonant four-wave sum-mixing process below the first resonance level of Ne.The conversion efficiency was found to be comparatively high because of the very small dispersion in this range.We found that the four-wave sum-mixing output was proportional to the square of the gas density we offered.If we increase the gas density of Ne,the conversion efficiency is estimated to be improved by two orders.
1997, 46 (2): 306-313.
doi: 10.7498/aps.46.306
Abstract +
We investigate the crystal structure and the spontaneos evolution of the silver oxide(Ag2O) ultrafine particles(UFP) produced by the vacuun-sputtering method.By using transmission electron microscopy and wide angle X-ray diffractometer and X-ray photoelectron spectrometer,the morphology and nanostructure and size distribution of UFP were measured and analysed.The process of the spontaneos evolution of UFPs was discussed by the spectrum fractal and thermodynamic potential and size-dependence of particles.It was suspected that the self-reduction decrystallization and decompose of crystal Ag2O UFPs might be intrinsic property of the ultrafine structure when the size of aggregate was less than the critical value.Furthermore,The reduced silver atoms have secondary recrystallization effect.
1997, 46 (2): 314-323.
doi: 10.7498/aps.46.314
Abstract +
By measuring the dielectric properties,we have found experimentally that the studied ER fluids underwent interfacial polarization and showed nonlinear dielectric properties under high AC field.Considering the dynamical shear stress to be similar to the high field dielectric spectra of the ER fluids,we have established a relation of dynamical shear stress to the high field dielectric spectra of the ER fluids and obtained the lower response times of rheology for two ER fluids.furthermore,it is found the dynamical shear stress of the NaY zeolite ER fluids was related to the intensity of its nonlinear THG,and the humidity of a semiconductor polymer has no effect on the rheological response.The experiment findings have been illustrated.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
1997, 46 (2): 324-331.
doi: 10.7498/aps.46.324
Abstract +
By use of the self-consistent linear field theory, three-dimensional perturbation of electrons affected by the perturbed electromagnetic fields is discussed. And Cherenkov radiations excited by a thin annular relativistic electron beam in a unmagnetized-plasma-filled, dielectric lined slow-wave waveguide are analysed. The dispersion equation and the wave growth rate of the interaction of the electron beam to the waveguide modes with arbitrary azimuthal mode number are derived. It′s clearly shown that the Cherenkov radiation results from the coupling of the waveguide mode in the unmagnetized-plasma-filled, dielectric lined slow-wave waveguide to the beam mode via the electron beam. Finally, the effects of plasma density on the dispersion relation and the wave growth rate are calculated and discussed.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
1997, 46 (2): 332-339.
doi: 10.7498/aps.46.332
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This paper is a systematic study of the real space dynamical electron diffraction involved in propagation calculation and sets down guidelines based on theoretical analysis for consistent and accurate computation for real space dynamical electron diffraction.
1997, 46 (2): 340-344.
doi: 10.7498/aps.46.340
Abstract +
The vibrational properties of spherical nanocrystal Si were studied and the relation between the size and Raman shift was established. It was found that the size of porous Si, simulated by Si spheres, should be much smaller than commonly reported.
1997, 46 (2): 345-352.
doi: 10.7498/aps.46.345
Abstract +
In order to investigate the non-equilibrium features in first order phase transition driven by a linear temperature field, the equilibrium free energy of the phase transition system was modified with an additional term, which is related to dη/dT or dη/dt. On the basis of the numerical solutions, the asymmetrical hysteresis behavior has been discussed.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
1997, 46 (2): 353-362.
doi: 10.7498/aps.46.353
Abstract +
The effect of electron-electron interaction on the localization of soliton is studied. Because the conducting polymer possesses wide bandwidth, the Hubbard model is no longer a suitable approximation. It is needed to use a screened Coulomb potential to describe the e-e interaction. Our theory shows that the screening plays a key role in the effect of e-e interaction on the localization of soliton: in weak screening, the localization of soliton will be enhanced by the e-e interaction; in strong screening, it will be reduced. In the end, the physical reason of above-mentioned results is explained by analysing the relation between screening and electron correlation.
1997, 46 (2): 363-369.
doi: 10.7498/aps.46.363
Abstract +
Does electron interaction enhance or reduce the creation energy of soliton? The results based on different theories conflict with each other. In this paper, the reason for such conflict has been revealed and a new method is proposed to calculate the creation energy of soliton (only intensive quantities are involved in calculation). Our result shows: the electron interaction enhances the creation energy of soliton, but the enhancement of the soliton is less than that of-e-h pair.
1997, 46 (2): 370-374.
doi: 10.7498/aps.46.370
Abstract +
The 2p± and 3p± excited lines of P donors in Si0.92Ge0.08 epitaxial layer have been observed using photothermal ionization spectroscopy.The ionization energy of P in Si0.92Ge0.08 is 45.51meV according to effective mass approach.The spectral lines of P in Si1-xGex compared with those in pure Si apparently broaden due to alloy disorder effect.
1997, 46 (2): 375-386.
doi: 10.7498/aps.46.375
Abstract +
Carrier transport through an n-type semiconductor grain boundary with a double Mott barrier consisting carrier depletion layers,acceptor defect layers (ACLs) on grain surface and negative-charged interface by trapping of majority carriers is studied.The effect of ACL on the barrier,current,nonlinearity and capacitance is especially treated.The change of barrier under bias governs transport properties,and ascertains the existance of pre-breakdown,breakdown and upturn regions.ACLs result in a change of barrier and its intensifying decline under bias,and thus enhance the current change and nonlinearity,and largely determine the leakage current.And ACLs reduce capacitance at high frequency by broaden barrier but increase capacitance peak originated from the resonant response of interface charge under bias.
1997, 46 (2): 387-392.
doi: 10.7498/aps.46.387
Abstract +
In situ DC resistance measurements were performed on semicontinuous niobium and silver films,which were made on mica and fullerene substrates in an ultra-high-vacuum chamber.Right after the interruption of the deposition,we investigated the changes (relaxation) of the sample resistance on a time scale of about 10 minutes.Resistance increase was observed for Nb/mica and Ag/C60 systems,and decrease for Ag/mica system.The relaxation is sensitive to substrate temperature and film thickness.We suggest that the edge diffusion and mergence of islands due to thermomigration of the metal atoms are responsible for the resistance relaxation.The intensity and direction of the relaxation reflect the interfacial activity of the metal/substrate system.The heterogeneities on substrate may also play an important role during this process.The analysis is presented from the angle of atom-migration and of thermodynamic evolution.
1997, 46 (2): 393-399.
doi: 10.7498/aps.46.393
Abstract +
The method of the plane-wave expansion of envelope functions,as applied to calculating the subband structures in superlattices,is extended to the 8-band k·p Hamiltonian,in which both Γc1 and Γv15 bands are included.In this method,we can easily take into account of the effects of the nonparabolicity,the discontinuity of the effective masses,the spin-orbit splitting and the inversion asymmetry on subbands.Using this method,we have computed the electronic structure and the optical transition probability of two superlattice systems,in which the in-plane polarized interconduction subband transitions were observed.Our results show that the probability of such transitions is very small.It is thus expected that there might be other machanism to be responsible for the experimental results.
1997, 46 (2): 400-405.
doi: 10.7498/aps.46.400
Abstract +
A new method,which involves measurement of the piezoelectricity by nuclear quadrupole resonance spectrometer,is proposed.The spectral intensity of a quartz crystal versus the strength of the excitation pulse,the pulse width and the resonance offset is studied in detail.The experimental results demonstrate that the piezoelectric resonance signal originating from samples located tens of centimeter away from the probe may be detected in a time scale of seconds.This technique provides potential for more extensive investigation and application of the piezoelectric materials.
1997, 46 (2): 406-410.
doi: 10.7498/aps.46.406
Abstract +
The interaction between hydrogen and defects in annealed,473K tempered and cold-rolled nickel samples has been investigated by positron lifetime and Doppler broadening measurements.Experimental results show that there has been no effect of hydrogen-charging on the nickel samples containing only dislocations,while in the samples containing vacancies the effect was evident.A long-lifetime component appeared for the latter,which may indicate that the hydrogen-vacancy composite is also the center of vacancy agglomeration.
INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
1997, 46 (2): 411-416.
doi: 10.7498/aps.46.411
Abstract +
The magnetic order in Cr75(Fe0.67Mn0.33)25 alloy prepared under different annealing conditions is studied by means of 57Fe Mssbauer spectroscopy and bulk magnetization measurements.We get the conclusion that the short-range chemical order plays a dominant role in the magnetic order of the alloy.The heat treatment process affects the Cr(Mn)-rich,Fe-rich clusters in the alloy,thus increases both the ferromagnetic and antiferromagnetic transition temperature greatly.The Cr(Mn),Fe clusters lead to the magnetic phase segregation in the alloy.
