Vol. 47, No. 8 (1998)
1998-04-20
GENERAL
1998, 47 (8): 1233-1240.
doi: 10.7498/aps.47.1233
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The problem of a harmonic oscillator of time-dependent frequency confined in a one-dimensional infinite square well with a moving wall is studied.It is shown that the exact solution and the Lewis invariant operator of the system can be obtained by performing two consecutive gauge transformations on the time-dependent Schrdinger equation.On the basis of the exact solution the Berry phases for the system are calculated by using the geometric concepts such as the geometric distance and geometric length of the curve.
ATOMIC AND MOLECULAR PHYSICS
1998, 47 (8): 1241-1247.
doi: 10.7498/aps.47.1241
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In this article,by using the adiabatic approximation and variational principle and introducing an effective potential we have computed some energy levels of hydrogen atom in the presence of a strong magnetic field(1≤β≤2000) and compared our results with the like multi-configuration Hartree-Fock method.We found a basic function with better convergence than the Landau function.
1998, 47 (8): 1248-1257.
doi: 10.7498/aps.47.1248
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We have studied the properties of the classical dynamics of three ions with collinear configuration in a Paul trap.We found that no chaotic motion exists,and the motions of the ions are regular at any given energy E.The trajectories of the ion ensemble in phase space are of the anti-symmetric type and symmetric type periodic(or quasi-periodic) orbits,which are constrained in two KAM tori respectively.The simplest trajectories of the ensemble are periodic orbit A and periodic orbit S.When E tends toward the minimum energy Emin=3.0 of the ensemble,the motions of A orbits and S orbits tend towards the anti-symmetric and symmetric harmonic oscillations,respectively.
1998, 47 (8): 1258-1264.
doi: 10.7498/aps.47.1258
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The influence of the different gas ratios (SO2/Ar) on the vibronically resolved laser-induced fluorescence excitation spectra of the SO2( 1A2— 1A1) system was investigated under the supersonic jet conditions.High resolution spectra of two complete progressions (1,m,1),(0,n,1) were obtained,in which the rotational structures of the (0,9,1),(0,10,1),(1,7,1),(1,5,1)-(0,0,0) bands were observed,for the first time,so long as we know.The assignments of 847 rotationally resolved lines were based on an asymmetric top simulation,which results in the determination of the rotational and centrifugal distortion constants of each vibrational level of state.The approximate geometry parameters of state was derived to be r(S—O)=0.160nm,∠OSO=101.64°.In addition,a discussion on the inertial defect of each vibrational level of state was presented.
1998, 47 (8): 1265-1271.
doi: 10.7498/aps.47.1265
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This paper reports the experimental observation of the excitation energy transfer to higher states by collisions between two rubidium atoms excited to a specific state by a CW single mode laser. An obvious competition has been observed between the channel of transition to the ground state by spontaneous emission, and that to higher excited states by collisions of two excited atoms. Formation rates of the high excited states with different laser power, atomic vapor temperature and laser detuning have been measured. A proposed mechanism well explained the experimental result.
1998, 47 (8): 1272-1277.
doi: 10.7498/aps.47.1272
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The relative elastic differential cross-sections(EDCSs) of 2500eV electrons scattered by helium,neon and argon atoms were measured at a scattering angle range of 4°—15°.The absolute values of these EDCSs were obtained by normalizing the relative values to the known generalized oscillator strengths.The final results were compared with previous experimental and theoretical results.
CLASSICAL AREA OF PHENOMENOLOGY
1998, 47 (8): 1278-1288.
doi: 10.7498/aps.47.1278
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This paper discusses the electromagnetic field distribution in phase grating and the rate of diffraction for different diffraction orders by using a rigorous modal theory. Piece wise analytical function is used to express the eigen functions instead of the infinite series in other methods. Stable, fast and accurate recurrent formulae are developed to calculate the reflection transmission and amplitude coefficient matrix that can treat phase grating with any number of groove steps. The numerical results show that there exist bands of total reflectance. The conditions and the physical mechanisms for which the total reflectance occurs are discussed.
1998, 47 (8): 1289-1295.
doi: 10.7498/aps.47.1289
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Taking into account the size effect of the source and the detector, we have calculated the Optical transfer function of a real system with Gaussian distribution of the source. Because of the Gaussian distribution source , the size of source and detector can be enlarged, and the signal-to-noise ratio will be increased.
1998, 47 (8): 1296-1303.
doi: 10.7498/aps.47.1296
Abstract +
It is shown that the Λ quantum beat system, into which a new atomic coherence is introduced, can produce bright two-mode sub-Poissonian light. The Mandel Q parameter is calculated using Scully-Lamb theory. On one hand, when quantum noises of the relative amplitude and relative phase drop to vaccum noise levels, the average mode exhibits sub-Poissonian photon distribution; when quantum noises of the average amplitude and average phase drop to vaccum noise levels, the relative mode exhibits sub-Poissonian photon statistics; the optimum Mandel Q parameter is -0.5. On the other hand, in the above two cases, each of the correlated spontaneous emission laser modes exhibits sub-Poissonian photon statistics with optimum Mandel Q parameter of -0.25.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
1998, 47 (8): 1304-1310.
doi: 10.7498/aps.47.1304
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Low-energy electron diffraction (LEED) shows that glycine molecules can stick onto the Cu(100) substrate at room temperature forming ordered structures, while their binding to the substrate is fairly weak as evidenced by the quick degradation of the adsorbing structures and in turn the LEED pattern induced by the incident electron beam. Scanning tunneling microscopy (STM) observation shows that the molecules can also adsorb on the Cu(111) substrate at room temperature, and the binding is strong enough to be imaged with not too small a tunnel resistance but is weak enough to be manipulated by the tip with a small tunnel resistance. Careful inspections of the STM images allow us to further conclude the following.(i) At least three adsorption geometries with different apparent heights have been identified, although the details of the molecular images are often dominated by the tip shape.(ii) It is possible to move the molecules without changing their adsorbing geometry. (iii) In manipulation the molecules are pushed forward by the tip.(iv) Each glycine molecule forms at least two bonds with the substrate. During controllable manipulations the molecules remain at least one bond unbroken. (v) Electrostatic forces between the tip and sample do not play an important role in manipulations, as changing bias polarity seems to have almost no influences.(vi) In manipulations the higher the tunnel resistance the better our control on the molecules, as long as the molecules can be moved.
1998, 47 (8): 1311-1317.
doi: 10.7498/aps.47.1311
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A monomer with reactive diacrylate was mixed with a commercial ferroelectric liquid crystal(FLC) mixture and polymerized under U.V. irradiation together with the application of an electric field of ±50V and 10Hz to obtain polymer network stabilized ferroelectric liquid crystals(PNSFLC). Polarized microscope and scanning electron microscopy(SEM) were used to study the molecule texture and the polymer network structure. It is found that the polymer network formed in the SmC phase is anisotropic and fibrils-like , and the PNSFLC cell shows a striped texture. The striped texture is explained by the elastic free energy theory.
1998, 47 (8): 1318-1324.
doi: 10.7498/aps.47.1318
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Using a homogeneously aligned cell as a holder for liquid crystols, we have investigated the polarization dependence of FT-IR of the stretching of CD2 in chiral alkyl chain of TFMHxPOBC-D2(4-(trifluoromethylhexy-3-d2 carbonyl)phenyl 4'-octyloxybiphenyl caboxylate) and observed the hindered rotation of the chiral alkyl chain for the first time to our knowledge. Simulation on the IR polarized absorbance leads to an angle of 70° between the chiral alkyl chain and the molecular axis.The biased direction and the tilt direction of molecules are toward the same side.
1998, 47 (8): 1325-1331.
doi: 10.7498/aps.47.1325
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The molecular dynamics method is employed to simulate motions of monovacancies in the ordered intermetallic compound NiAl using Finnis-Sinclair N-body potentials.It is shown that the antistructure bridge mechanism is important at compositions deviated from stoichiometry, and near the stoichiometry, the six-jump cycle, the staight ［100］-type for Al vacancy and ［110］-type cycle for Ni vacancy, are energetically favorable. The calculated results, which are consistent with experimental measurement, clarify the recovery behavior of defects in NiAl quenching experiment.
1998, 47 (8): 1332-1338.
doi: 10.7498/aps.47.1332
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In stabilized-ZrO2 with high-purity, the space-charge contribution plays a dominating role in the grain-boundary resistance. A grain-boundary conduction model is proposed on the basis of this concept, and the effect of the segregations of calcium, yttrium and aluminium on the space-charge conduction is discussed, the segregations are all found to decrease the space-charge conduction, thus increase the grain-boundary resistance. Some formerly-established concepts are evaluated via the model, the limitation of the complex impedance approach based on the Bauerle′s equivalent circuit is pointed out, and the defect of the concept of the resistance per unit interface area of the grain boundaries is also discussed.
1998, 47 (8): 1339-1345.
doi: 10.7498/aps.47.1339
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The conduction-band offset ΔEc has been determined for molecular beam epitaxy (MBE) grown GaAs/In0.2Ga0.8As single quantum well structure,by measuring the capacitance-voltage profiling, while taking into account a correction for the interface charge density, and the capacitance transient resulting from thermal emission of carrier from the quantum well, respectively.We found that ΔEc=0.227eV,corresponding to about 89% ΔEg,from the C-V profiling; and ΔEc=0.229eV, corresponding to about 89.9% ΔEg, from the deep level transient spectroscopy (DLTS) technique. The results suggest that the conduction-band discontinuity ΔEc obtained from the C-V profiling is in good agreement with that obtained from the DLTS technique.
1998, 47 (8): 1346-1353.
doi: 10.7498/aps.47.1346
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Uniform triangular dots (TDs) and ridge dots (RDs) structures are grown by moleculat beam epitaxy (MBE) on square mesa and hole patterned (311)A substrates. The surface morphology and cross-sectional characterization of the dot structures investigated by atomic force microscopy(AFM) and scanning electron microscopy(SEM) show that the TDs and RDs structures are formed on the hole and mesa patterned areas during the growth. TDs are one-side pinch-off structure evaluated between the holes with highly uniform tips along ［233］ direction, and the RDs two-side pinch-off structure accomplished on the mesa with ordered two opposite tips, respectively. The AFM line-scan height profiles of the dots structures indicate that the TDs and RDs structures are dominated by the Ga adatoms preferential migration from symmetric (331)A side walls of the mesa and holes to the bottom region to develop the triangular shaped tips structure, while the facet orientation of the tips is determined by the original side walls orientation of the mesa and hole to lead to form uniform pinch-off arrays. The cathode luminescense measurements reveal that the line,dot,ring-like lateral variations of quantum well confinement energies are formed in the regions of the TDs and RDs structures. These unique growth phenomenon provides a good possibility to realize three-dimensional quantum confinement structures by using MBE growth on (311)A substrates with much smaller length scale of patterning.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
1998, 47 (8): 1354-1360.
doi: 10.7498/aps.47.1354
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By using quantitative mobility spectrum analysis technique, the temperature-dependent density and mobility for each subband of the accumulated layer on the n-HgCdTe devices have been determined from magnetic-field-dependent Hall and resistivity data.The results agree well with the Shubnikov-de Hass measurements and theoretical calculations.
1998, 47 (8): 1361-1368.
doi: 10.7498/aps.47.1361
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The infrared spectra of PrBa2Cu3O6+x (x=1, 0.3) ceramics and films with c-axis orientation are reported in this paper, and the phonon modes in c-axis and ab-plane are distinguished by treating the different vibrational behaviour for film and ceramic samples. Due to the fact that PrBa2Cu3O6+x possesses the similar crystal structure as RBa2Cu3O6+x (R=Y and other rare earth elements), by comparing the phonon spectra, espeacially the B1u (x=1), Eu and A2u (x=0.3) modes of Pr, Y and other rare earth elements, it is found that the valence value of Pr depends on the oxygen content, i.e., the Pr valence is 3+ in PrBa2Cu3O6.3 while it is larger then 3+ in PrBa2Cu3O7.
1998, 47 (8): 1369-1377.
doi: 10.7498/aps.47.1369
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The properties of dc-SQUIDs with a resistively shunted inductance(Rdc-SQUID) were theoretically analyzed. The dependencies of Sv,S1/2,and dv-/da on the bias current ib for Rdc-SQUID were presented. The advantages of the high-Tc dc-SQUID magnetometer with using Rdc-SQUID have been discussed. A chip of high-Tc dc-SQUID magnetometer with modulation parameter β=4 and damping parameter γ=0.5 was designed under the conditions of the depositing and lithographic technology in laboratory. A gold thin film (≈50nm thickness and 10μm width) was deposited on the superconductive loop as the damping resistance. The theoretical values of S1/2Φ and S1/2B for the magnetometer are respectively 2.4×10-6Φ0/Hz and 200fT/Hz. Comparing the properties between dc-SQUID and Rdc-SQUID,the experimental value S1/2B,which is about 400 fT/Hz,for the magnetometer directly coupling with a 8 mm- input coil was estimated.
1998, 47 (8): 1378-1382.
doi: 10.7498/aps.47.1378
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The infrared thin film detector is prepared consisting of (Mn,Sb)-doped PZT and high-temperature superconductor YBCO films. It is of a performance of self-polarization and is able to operate at room temperature. The relationships of infrared photovoltage and photocurrent of the detector with blackbody infrared source temperature, detector sample temperature and chopper frequency, are described.
1998, 47 (8): 1383-1390.
doi: 10.7498/aps.47.1383
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An electrothermodynamic analysis of field evaporation in the configuration of scanning tunneling microscope(STM) has been performed. By introduction of an effective binding energy, a formula for the evaporation field in STM has been constructed. The calculated evaporation field for Au-1, for the first time to our knowledge, agrees well with experiment. On the other hand it was found that the classic charge exchange model and image hump model yield very high evaporation field because they require that the adatoms be fully ionized and evaporated to infinity.
INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
1998, 47 (8): 1391-1396.
doi: 10.7498/aps.47.1391
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The temperature dependence of photoluminescence (PL) in porous silicon has been investigated. It is found that the PL peak from the low porosity samples shows a red shift with decreasing temperature, but the blue shift of the PL peak is always observed in the high porosity samples. The temperature dependence of the PL peak shift observed experimentally can be qualitatively explained by the simulated curves of the luminescent efficiency versus wavelength.
1998, 47 (8): 1397-1403.
doi: 10.7498/aps.47.1397
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In this paper, a new mechanism of anti-Stokes fluorescent cooling based on the energy transfer among the centers within the inhomogeneously broadened line is proposed. The dependence of relative cooling efficiency on excitation photon energy and temperature is discussed.
GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS
1998, 47 (8): 1404-1408.
doi: 10.7498/aps.47.1404
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This paper gives the nonlinear analyses of the core 3He nuclear reaction diffusion system. It is shown that the system can be led a sudden change to a new supercritical space structure from the original steady——state after the effects of convection and diffusion are taken into account, and the production rate of 3He changes and the total of its density increases. The 3He may be denser in a limited local region so that the reaction rate of 3He+3He is accelerated to have a high energy generation in the region. The understanding for the solar core is also given.
