Vol. 45, No. 6 (1996)
1996-03-20
GENERAL
1996, 45 (6): 897-903.
doi: 10.7498/aps.45.897
Abstract +
First we put forward an essential condition, for the existence of the non-zero adiabatic geometric phase of a quantum-mechanical Hamiltonian system, that the Hamiltonian operators at different times do not commute. Then it is shown that constraint =0 determines completely the phase relation of normalized eigenstate vectors │n' (t)> at different times. According to this property, we advance the sufficient and necessary condition for the existence of the non-zero adiabatic geometric phase, which is |n′(T)>≠|n′(0)> when =0. And also we derive a general time-integral formula for the adiabatic geometric phase along the line. Finally, as an application of it, we calculate the geometric phase of a spin 1/2 system once discussed by Solem and Biedenharn. It is pointed out that the problem encountered by them lies in the multi-valuedness of the eigenstate vector in parameter space.
1996, 45 (6): 904-911.
doi: 10.7498/aps.45.904
Abstract +
The topological properties of the delay-time reconstruction transformation of dynamic system are analysed by means of the Jacobian of the transformation. Results show that the topological properties depend not only on the reconstructing dimension, but also on the delay time, and on the conditional stability of a time series itself. The conditional Lyapunov exponent is used to judge whether a time series is good or bad. As an example, the R?ssler system is discussed.
1996, 45 (6): 912-923.
doi: 10.7498/aps.45.912
Abstract +
The generalized invariant theory is used to study the problem of the diagonalization of the time-evolution operator. It is shown that there is an intimate connection between the diagonalization of the time-evolution operator and the phase factors. As an illustrative example, the quantum motion of an ion in a combined trap is investigated; the classical correspondence of the quantum motion and the stability problem are then discussed.
CLASSICAL AREA OF PHENOMENOLOGY
1996, 45 (6): 924-928.
doi: 10.7498/aps.45.924
Abstract +
High-power ( 200 kV), intense-current-density, low-emittance, high-brightness electron beam was generated in a 10 gap pseudospark chamber filled with 15 Pa N2 and driven by an improved pulse line accelerator. The ejected electron beam was characterized by 1mm diameter, 2. 2 kA beam current, and 400ns pulse length, and propagated 20cm in neutral N2 ionizing channel in the drift tube. At 5 cm downstream of the anode, it penetrated consecutively an acid-sensitive discoloring film and a 0.05 mm-thick copper foil, and left 0.6 mm and 0.3 mm holes on them, separately. According to the pinching equilibrium condition, the beam's normalized emittance and brightness are respectively calculated to be 23 πmm-mrad and 8×1010A/(m rad)2. That the 10 shots on the same acid-sensitive film produced a hole of 1. 6mm in diameter at 7cm showed a good repeatability of the electron beam. After 60 shots the pseudospark chamber was observed that there was almost no destructive damage traces left on the surfaces of the electrodes and insulators. It was found that the quality of electron beam produced in the pseudospark discharge chamber driven by the modified pulse line accelerator is much better than that generated by cold cathode discharges.
1996, 45 (6): 929-939.
doi: 10.7498/aps.45.929
Abstract +
The optical bistability (OB) of intersubband transitions in a semiconductor superlattice is stu -died by applying the general formalism of the Kronig-Penney model and density matrix method. The Maxwell-Bloch (MB) equations of two-subband model are derived, and the OB state equation for a ring cavity is obtained from the stationary solution of the MB equations. The conditions for realizing the OB and its characteristics are discussed.
1996, 45 (6): 940-945.
doi: 10.7498/aps.45.940
Abstract +
The effects of an applied electric field on the recording and erasing characteristics of the fundamental and higher-order harmonics of the space-charge field inside the crystal are observed and measured at wavelength of 633 run with a Ce-doped KNSBN crystal. The experimental results obtained are analyzed and explained.
1996, 45 (6): 946-952.
doi: 10.7498/aps.45.946
Abstract +
The higher-order fundamental quantum-mechanical fluctuation is given on the base of the higher-order uncertainty relation, from which the definition of higher-order squeezing for atomic dipole is introduced. As an example, we examine the second-, fourth-and sixth-order squeezing of atomic dipole in the two-photon Jaynes-Cummings model with the two-photon superposition state preparation.
1996, 45 (6): 953-959.
doi: 10.7498/aps.45.953
Abstract +
Ionization in a magnetically confined argon discharge has been studied by the use of a Monte Carlo simulation. Especially, influences of the transverse magnetic field have been investigated for a pressure range of 30 Pa-4 kPa. It is found that the magnetic field acts effectively only in a definite range of pressure( < 600 Pa), and within the range there is an optimum strength for the field. Analyses for the results and consideration of applying the discharge in ion lasers as well as in sputtering-based metal vapor lasers have been given.
1996, 45 (6): 960-965.
doi: 10.7498/aps.45.960
Abstract +
A novel Er3+- doped ring fiber laser with simple structure is proposed in this paper and self -pulsing is observed under the lower pump parameters. The effects of pump parameters and the length of single mode fiber in the loop on the self-pulse characteristics are investigated experimentally. The results show that the self-pulse characteristics can be controlled by the adjustment of the relative parameters properly.
1996, 45 (6): 966-976.
doi: 10.7498/aps.45.966
Abstract +
In this paper the theoretical and experimental studies on the properties of phase conjugate (PC) wave and the gratings formed as a result of degenerate four-wave mixing (DFWM) interference field of Ar+ laser in bacteriorhodopsin-polyvinyl alcohol (BR-PVA) solid film are reported. The diffraction efficiency temporary response and saturation property of the PC wave are described by useing a simplified double state model and the method of rate equation combined with a diffraction theory of holograph grating. The mechanism of forming grating in the film and the dependence of the properties mentioned above on polarization states, intensities are analysed. The time of arriving at the sample of three input beams and initial concentration of grating formed in the film are discussed. The theoretical results are in good agreement with the experimental observations.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
A MATRIX METHOD DESMEARING THE DISTORTION CAUSED BY SLIT COLLIMATOR SYSTEM IN SMALL ANGLE SCATTERING
1996, 45 (6): 977-984.
doi: 10.7498/aps.45.977
Abstract +
A new matrix desmearing method in small angle scattering (SAS) has been developed. The feasibilities make it may be applied conveniently to all types of SAS spectrometer which have to use slit collimatior system at the research reactor with low and medium flux. The experimental results show that the method is consistent with the ordinary desmearing method.
1996, 45 (6): 985-989.
doi: 10.7498/aps.45.985
Abstract +
Phase transitions on a clean reconstructed Si(100)-c(8×8) surface induced by atomic hydrogen adsorption at different temperatures have been studied using low energy electron diffraction (LEED) . It has been found that: at liquid nitrogen temperature, successive dosing of atomic hydrogen cause the surface go through a series of phase transitions from c(8×8)to(4×l)-H to(2×l)-H and finally to (1×1)- H. At different temperatures from 700×3 down to room temperature, successive saturation doses of atomic hydrogen can induce phase transitions from c(8×8)to c(4×4)-H to (2×1)-H and finally to(1×1)-H.
1996, 45 (6): 990-994.
doi: 10.7498/aps.45.990
Abstract +
Using M?ssbauer spectroscopy, We have studied the structural characteristics of the alloy phases of three samples formed by the process of mechanical alloying. The starting compositions of these samples are 70B30,Fe55B45 and Fe30B70. The crystallization or transition of the amorphous phases under annealing has also been examined. It was found that a certain relation exist between the amorphous phases and corresponding Fe-B compounds.
1996, 45 (6): 995-1002.
doi: 10.7498/aps.45.995
Abstract +
We've investigated the annealing behaviour of the di-carbon centre (zero-phonon line at 969 meV or 7818 cm-1)in float zone and Czochralski silicon crystals. The break-up process is not the only way to destroy the di-carbon centres and it is shown that the presence of other defects may affect the annealing process. After the thermal destruction of the di-carbon centre, we've discovered many previously unreported carbon and oxygen related point defects. Their photolumiescence lines are observed. We suggest that the interstitial silicon atom is the defect trapped near but not ‘at' the di-carbon centre forming the satellite sublines at 951.16(7671), 952.98(7686), and 956.91meV (7717cm-1).
1996, 45 (6): 1003-1009.
doi: 10.7498/aps.45.1003
Abstract +
The properties of the surface phonon modes in spherical SnO2 nanometer particles were studied by the method of infrared spectroscopy. The sum total of Frohlich modes of SnO2 nanometer particles were reported in our experiments. The theoretical results of surface mode frequency of SnO2 nanometer particles were presented, which agreed well with those of experiments. Finally, the effects of quantum confinement on the infrared properties of SnO2 nanometer particles were discussed.
1996, 45 (6): 1010-1015.
doi: 10.7498/aps.45.1010
Abstract +
An accurate linear damping calculation formula for free vibration system has been deduced and the application limits of the corresponding approximate calculation formula has been discussed as well. Finally, the related experimental results have been calculated respectively by the newly-deduced formula and the present approximate one, and the two kinds of calculated results have been compared, analysed, and discussed.
1996, 45 (6): 1016-1025.
doi: 10.7498/aps.45.1016
Abstract +
Early since 1950, a systematic study was made on the anomalous internal friction peaks appeared in cold-worked Al-Cu and Al-Mg specimens around room temperature. The activation energy associated with these internal friction peaks was found to be close to that associated with the pipe diffusion along dislocations. Consequently the internal friction peaks were attributed to the diffusion of Cu or Mg atoms in the dislocation core in aluminium. A physical model of these internal friction peaks was suggested in terms of the dislocation kink concept. The manifestation of these anomalous internal friction peaks was found to be similar to that predicted through a detailed mathematical analysis of the dislocation core diffusion by Winkler-Gneiwek et al. according to the string model. In this paper, a critical comparison has been made between the string model and the kink model concerning this problem and it is shown that the predictions derived from the string model can be adequately applied to the case of the kink model. This confirms further that the nonlinear anelastic internal friction peaks we observed are originated from dislocation core diffusion.
1996, 45 (6): 1026-1032.
doi: 10.7498/aps.45.1026
Abstract +
Evidence has been found that solid solution of 10 mol% lead titanate in lead magnesium niobate bears strong resemblance to spin and dipolar glasses. The frequency dispersion of the temperature of the permittivity maximum, Tm, has been analyzed using the Vogel-Fulcher relationship. The difference between the solid solution and glass was discussed. Based on this analysis, a new ralationship:ω = ω0exp {- (T0/Tm)p},was introduced which is more suitable and effective for relaxor ferroelectrics to analyze the frequency dispersion of the temperature of the permittivity maximum than Vogel-Fulcher relationship. The dielectric relation of the solid solution was measured The results were analyzed using the new relationship, and activation energy of 0.037 eV was obtaived.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
1996, 45 (6): 1033-1038.
doi: 10.7498/aps.45.1033
Abstract +
Specific heat measurements have been made in K0.3MoO3 and Tl0.3MoO3 using an adiabatic continuous heating method from 100 K to 220 K. It is found that Peierl transitions occur at 177.5 K and 172.3 K for K0.3MoO3 and Tl0.3MoO3 respectively. Analyses of specific heat data near Peierls transitions yield that widths of critical regions are about 6 K and 8 K for K0.3MoO3 and Ti0.3MoO3 respectively and the critical behavior belongs to the three dimensional XY model.
1996, 45 (6): 1039-1045.
doi: 10.7498/aps.45.1039
Abstract +
The focusing ability of the image charges on annular beams is analyzed, and the image charge is on the conducting foils which are placed perpendicular to the beam axis. The given calculating results can be employed to select the geometrical parameters of the foils for annular beam focusing. The first image charge focusing relativistic klystron amplifier experiment was done to study the effects of the foils on the bunching process. Although the transparancy of the foils to the beam is only 0.88, the results show that the foils do not affect the beam bunching process.
1996, 45 (6): 1046-1050.
doi: 10.7498/aps.45.1046
Abstract +
The spectra of the dielectric constant vs. the measuring temperature and of the dielectric constant vs. the measuring frequency for the nanostructured rutile bulk samples prepared under different pressures were investigated. It can be observed that when the measuring frequency ω2 times higher than that in the high frequency range. Furthermore, with the increment of the pressure, the dielectric constant rises and dielectric loss decreases and shifts towards the low frequency. For the samples formed under 1.0 GPa, two peaks appear in the spectrum of dielectric constant vs. the measuring temperature, and their peak positions are 50℃ and 300℃ , respectively. According to dielectric polarization theory, it can be supposed that high dielectric constant of nanostructured rutile arises mainly from the electronic relaxation polarization, which takes place inside the particle components of nanostructured rutile, and the rotation direction polarization, which is established in interfaces of nanostructured rutile, The 50℃ peak and the 300 ℃ peak are, respectively, attributed to the electronic relaxation polarization and the rotation direction polarization.
1996, 45 (6): 1051-1058.
doi: 10.7498/aps.45.1051
Abstract +
In this paper, it is discussed that when monochromatic light incident normally on an arbitrarly making directional biaxial crystal. The formulas can be deduced for propagating directions of polarized light and the transmittance—reflectances of incident components. An important conclusion isobtained that directions of polarization are always on the refractive planes and the two refractive planes are perpendicular with ecch other. And finally, the numerical results are plotted in curvilineal diagrams for NaNO2, it is seen that the changes of the emergent points of polarized light and that of the reflectances are obvious as the crystal making directions change. These results offer a new possibility for determination of crystal optical constants.
1996, 45 (6): 1059-1067.
doi: 10.7498/aps.45.1059
Abstract +
In this paper, the Merten' s equation and dispersion relation of polaritons in the uniaxial crystal had been deduced from the generalized dispersion relation of the phonon-polariton. Raman spectra of every LO, TO mode and oblique phonons in BaTiO3 and Ce: BaTiO3 single crystals have been recorded, the directional dispersion curves are fitted on the basis of Merten's equation. Raman spectra of A1 polaritons with different wave-vector q have been measured and the high and low frequency dielectric constants in both BaTiO3 and Ce:BaTiO3 are calculated. Two broad asymmetry bands in A1(TO) Raman spectra and the mechanics of structure phase transition in BaTiO3 are also discussed. The influence of Ce on the structure of BaTiO3 single crystal are analysed.
INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
1996, 45 (6): 1068-1072.
doi: 10.7498/aps.45.1068
Abstract +
Growth of CN films on Si (111) is realized by ionized cluster beam (ICB) deposition. X-ray diffraction (XRD) shows the occurence of β-C3N4 crystal structure in the films. X-ray photoelectron spectra (XPS) shows 20% N incorporated into the films and two peaks are observed in C1s and N1s, core level spectra respectively. Single bonded CN and triple bonded CN were identifies by infrared absorption spectra. Reflection high-energy electron diffraction (RHEED) demonstracted the coexistence of amorphous and crystalline CN compounds. The Knoop hardness of CN films reaches 6200 kgf/mm2.
