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Vol. 41, No. 3 (1992)

1992-02-05
GENERAL
SYMMETRY GROUP AND HARMONIC POTENTIALS OF A MAGNETOSTATIC MULT1POLE
LI Yü
1992, 41 (3): 353-359. doi: 10.7498/aps.41.353
Abstract +
In this paper, a magnetostaric multipole with a control vector is studied. The relation between the symmetry transformation of this multipole and that of its M-tunction is derived. A rigorous, general and simple method for deriving the constraints of the symmetry group of this multipole on its harmonic potentials has beenset up.
AN ANALOG SIMULATION OF STOCHASTIC RESONANCE
QIN GUANG-RONG, GONG DE-CHUN, HU GANG, WEN XIAO-DONG
1992, 41 (3): 360-369. doi: 10.7498/aps.41.360
Abstract +
Stochastic resonance (SR) phenomena are investiged from various aspects by utilizing an electric circuit The mechanism of SR is discussed and the output signal-to-noise ratio (SNR) is measured. The signal may be extracted from strong noise due to energy transfer from noise to signal under the SR condition.
ATOMIC AND MOLECULAR PHYSICS
EFFECTS OF THE CORE POLARIZATIONS ON THE HYPER FINE INTERACTION OF THE TRIPLET (3d2)3P STATES OF ScII
XI JIN-HUA, WU LI-JIN
1992, 41 (3): 370-378. doi: 10.7498/aps.41.370
Abstract +
The hyperfine interaction constants of the triplet (3d2)3P states of Sell are calculated using Rayieigh-Schr?dinger perturbation method. The core polarizations are included to all orders using a recurrence formula and the correlations to low orders. The results are compared with experimental data and MCDF calculations of Young et al. It is found that the core polarization (especially the spin polarization) has drastic effects on the magnetic dipole interaction constant. Our results for constant A (MHz) are-116.667 and -12.442 for 3P1 and 3P2 states respectively, that of the experiments are-107.3(6) and -27.7(8), whereas the MCDF calculations of Young et al. obtained-1.8 and 85.9.
ESTIMATION OF LASER RESONANCE IONIZATION EFFICIENCY
ZHANG LI, SHANG REN-CHENG, XU SI-DA
1992, 41 (3): 379-386. doi: 10.7498/aps.41.379
Abstract +
This article is to solve the rate equations of laser resonance ionization for a three energy level system with little simplification. Three cases of utilizing continuous, quasi-continuous and pulsed laser are discussed respectively. The results of typical conditions presently available are given. The variation of the results with different parameters are discussed as well. The calculation method and program can be used for general purpose. As long as the necessary parameters have been determined, the program can be used for quantitative calculation of an experiment.
MULTIPHTON SPECTROSCOPY OF RYDBERG AND MIXED RYDBERG VALENCE STATES OF Cl2
E. HONTZOPOULOS, C. FOTAKIS, FU GUANG-SHENG
1992, 41 (3): 387-399. doi: 10.7498/aps.41.387
Abstract +
The structures and properties of highly excited Rydberg and mixed Rydberg-valence states of molecular chlorine have been studied in detail by combining ioniza-tion, excitation and fluorescence spectroscopic techniques following multiphoton exci tation. The position of the inner-well of 11∑u+ state is located, and the 21∑u+ state is found to exhibit a strong mixed Rydberg and ion-pair valence character. A new series with symmetry is discovered and a assignment to the excitation of Rydberg state 3∑u is suggested. Based on the experimental results, the processes of three photon excitation, interation of 21∑u+ with 11∑u+ states and spectral effects of third harmonic generation are discussed.
A STUDY ON ROTATIONAL RELAXATION OF GAS PHASE C2H2 BY RAMAN UV OPTICAL DOUBLE RESONANCE
H. ZACHARIAS, R. DOPHEIDE, GAO WEN-BIN
1992, 41 (3): 400-407. doi: 10.7498/aps.41.400
Abstract +
In the present work, the selective preparation of C2H2 in discrete rotational states of the infrared inactive vibrational v mode in its electronic ground state (X1∑g+,v″2=1,J″= 9,11 and 13) is achieved by stimulated Raman excitation. From the UV laser induced fluorescence, A1Au(v′3=←X′∑g+ (v"2=1), the C2H2-C2H2 collisional R-R deactivation rate constants are measured. They are (7.96±1.04)×10-10cm3s-1 for J"= 9, (8.79±0.97)×l0-10cm3s-1 for J"= 11 and (8.76±0.88)×10-10cm3s-1 for J" = 13. The multiquanta R-R energy transfer rcte constants for trdnsitions from the initial pumped level to other different rotational states (v"2= 1, J" = 1,3,5,7,9,11,13,15) have been extracted directly.
CLASSICAL AREA OF PHENOMENOLOGY
BEAM TEMPERATURE AND ENERGY BROADENING OF A HIGH-CURRENT HEAVY-ION BEAM IN AN AXIALLY SYMMETRIC ELECTRIC-FIELD
TIAN REN-HE, ZHANG HUI-XING
1992, 41 (3): 408-412. doi: 10.7498/aps.41.408
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In this paper, the beam temperature and energy broadening of a charged-particle beam in an axially symmetric electric-field (including the average field causel by the space charge) are presented. The result shows that in the drift region, this kind of energy broadening is directly proportional to the beam current and inversely proportional to the macro flow velocitp of the beam, so that for a heavy-ion beam with higher current, it will become an important part in the total energy broadening. As a numerical estimation, the energy broadening of a 1H ion beam with energy 20keV and current 20mA in the drift region is 26.5eV, while under the same conditions, the 121Sb ion beam has an energy broadening of 291.5eV which increases linearly with the increasing of beam current. The result about the beam temperature shows that in the drift region, the effect of space charge of the beam raises the beam temperature.
INSTANTANEOUS RESONANCE FLUORESCENCE SPECTRUM OF A TWO LEVEL ATOMIC SYSTEM DRIVEN BY AN EXPONENTIAL BY DCEAYING FIELD
TAN WEI-SI, TAN WEI-HAN, ZHAO DONG-SHENG, LIU REN-HONG
1992, 41 (3): 413-427. doi: 10.7498/aps.41.413
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The commutation relation and quantum mechanical Langevin equations for a two-levef system is evaluated at first. Then, the instantaneous fluorescence spectrum of atomic system driven by an exponentially decaying field is calculated.
HIGHER ORDER SQUEEZING OF MIXED SUPERPOSITION STATES
DONG CHUAN-HUA
1992, 41 (3): 428-436. doi: 10.7498/aps.41.428
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In this paper, we calculate the k-th moments of △a1 and △a2 in mixed superposition states, discuss the higher-order squeezing in these states with Bloch vector. We also describe and calculate squeeze zones, and squeeze conditions in higher-order squeezing, discuss some optimum squeeze conditions. We conclude that two quadrature components a1 and a1 can be squeezed to higher-order at the same time under some conditions. Finally, we try to discuss the nature of squeeze in superposition states.
LANGEVINIAN THEORY OF TWO-PHOTON LASERS BY OPTICAL PUMPING
HU XIANG-MING, WANG DE-XIN
1992, 41 (3): 437-441. doi: 10.7498/aps.41.437
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In this paper, a two-photon laser by optical pumping, with two-photon losses, is studied by means of the Langevinian theory, the langevinian equation is obtained. Then the steady-state average photon number, the frequency pulling, the linewidth and the dynamical Stark effect are obtained. From the analysis of the gain, it is shown that, for the incoherent pumping, only the two-step process of single-and two-photon gives contribution. And for the coherent pumping, in addition, the one-step process of single and two-photon also contributes. And two processes are confined by the negative-feedback and saturation. The linewidth is independent of the steady state average photon number.
A NOVEL SMALL-PERIOD WIGGLER FOR FREE-ELECTRON LASERS
FENC BI-BO, WANG MING-CHANG, WANG ZHI-JIANG, LU ZAI-TONG, ZHANG LI-FEN, FENG CHENG-SHI
1992, 41 (3): 442-447. doi: 10.7498/aps.41.442
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A novel small-period wiggler configuration constructed by sheet of bifilar-helix with ferro-core for free-electron lasers is proposed. The performance characteristics of the wiggler prototype with 10mm period are measured. The field as high as 500G to 1kG have been obtained. The amplifier designs for operation at 190 GHz using modest electron beam energies in the range of 400-500 keV are presented.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
INVESTIGATION ON ELECTRICAL PROPERTIES AND ESR OF AMORPHOUS Li+ CONDUCTOR B2O3-0.7Li2O-0.7LiCl-xAl2O3-0.1V2O5
SU FANG, JIN SI-ZHAO, SU JUN
1992, 41 (3): 448-458. doi: 10.7498/aps.41.448
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Two kinds of amorphous Li+ conductor, B2O3-0.7Li2O-0.7LiCl-xAl2O3-0.1V2O5(x= 0.05 and 0.15), were studied with differential thermal analysis, conductivity measurement, X-ray diffraction and ESR spectroscopy. We find that: (1)V2O5 not only is amorphous network former, but also changes the process of crystallization;(2) For both the B2O3-Li2O-LiCl-Al2O3-V2O5 glasses and the P2O5-Li2O-LiCl-Al2O3 glasses,ionic conductivity of the tablet sample is 26 times higher than that of 60 mesh powder sample of the same material; the whole piece of glass has an obviously lower activation energy and a conductivity that is two orders higher than that of the tablet sample, so it is more suitable for ion transport; (3) Adding V2O5 less than 3.9mol% to amorphous Li+ conductor B2O3-0.7Li2O-0.7LiCl-xAl2O3(0≤x≤0.15) does not cause electron-conductivity to increase rapidly. Further more, this makes it possible to apply the technique of ESR to study the micro structure of and electron movement in the material.
ADSORPTION OF CO ON Cu{001}c(2×2)-Pd ORDERED SURFACE ALLOY
Lü SI-HUA, WU SI-CHENG, LIU GUO-LIANG, YAO JUN LIU, FENG-QIN
1992, 41 (3): 459-464. doi: 10.7498/aps.41.459
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The site of CO adsorbed on Cu {00l}c(2×2)-Pd ordered surface alloy has been studies using high resolution electron energy loss spectroscopy (HREELS). CO molecules are bonded vertically only on top sites of Pd atoms at 240K. At 135K, CO molecules are bonded vertically on top position of Pd atoms also under low coverage, and CO adsorbed both on top site of Pd and Cu atoms under high coverage.
INFLUENCE OF ARGON ADDITION ON THE GROWTH OF DIAMOND-LIKE FILM
ZHAN RU-JUAN, HUANG WEI-DONG, ZOU ZU-PING, WANG YAN-XIA, XIANG ZHI-LIN, GAO KE-LIN
1992, 41 (3): 465-470. doi: 10.7498/aps.41.465
Abstract +
In deposition of the diamond-like films by electron assisted plasma chemical vapor deposition, two systems (CH4/H2 and CH4/H2/Ar) have been used and compared. The electron temperature and electron density have been measured by means of Langmuir single probe. The results show that the electron density in CH4/H2/Ar is higher than that in CH4/H2, and the growth rate of the films increases in CH4/H2/Ar system.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
MS-Xα CALCULATIONS OF CHROMIUM ION IN DIFFERENT VALENCE STATES WITH SIX LIGANDS
YANG BAO-CHENG, LIN YUAN-GI, SHEN ZHONG-JUN, ZHENG YI-SHAN, ZHU JI-KANG, ZHU SHENG-XIANG
1992, 41 (3): 471-478. doi: 10.7498/aps.41.471
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In this paper, the electronic structures of the complex ions (CrO6) in three different valence states of chromium ion (Cr2+, Cr3+, Cr4+) are calculated with the spin-polarized MS-Xaaaa method. The one-electron eignvalues and eignfunctions, the energy levels, and the optical transitions under the D4k symetry are given. The calculated results are discussed comprehensively.
ELECTRON CORRELATION IN ONE-DIMENSIONAL CONDUCTING POLYMERS (11111111) NEUTRAL SOLITON
SUN XIN, MEI LIANG-MO, HU WEI-JUN
1992, 41 (3): 479-484. doi: 10.7498/aps.41.479
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In this paper, electron-electron correlation in one-dimensional conducting polyers is studied in detail. A new idea, i.e., that of "over-average interaction amoug eltctrons", is introduced. By considering the nearest-neighbor interactions, and on-sitt, site-site, site-bond, and on-bond terms a model Hamilitonian is proposed. The calculated numerical results are in good agreement with that of the optical absorption experiments and the ENDOR experiments on the neutral soliton in trans-(CH)x.
X-RAY IRRADIATION EFFECT IN a-Si SOLAR CELL AND ITS BELOW-GAP PHOTOCURRENT SPECTROSCOPY OBSERVATION
WEI GUANG-PU
1992, 41 (3): 485-490. doi: 10.7498/aps.41.485
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X-ray irradiation effect in hydrogenated amorphous silicon (a-Si:H or a-Si) solar cell has been observed. The results show that the photovoltaic characteristics decrease with the increasing of X-ray irradiation dose at first, and then tend to a steady state. By the below-gap photocurrent spectroscopy measurement, the change of defect density in a-Si induced by X-ray irradiation was studied. The results show that the defect density increase with the X-ray irradiation dose.
A STUDY ON PROPERTIES OF Au-DOPED SILICON
CHEN MIN-RUI, SHEN YI-HUI, LIU SHI-YI
1992, 41 (3): 491-499. doi: 10.7498/aps.41.491
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In this paper infra-red absorption spectra and surface photovoltaic spectra of An-doped and undoped silicon are studied. The relation of minority carrier diffusion length to the height of base line of infra-red absorption spectra under the same surface condition is determined. By using semiconductor statistics, we obtain the Au-doped silicon semicondutor statistics formulae when the degeneracy factor is different from unit, as well as silicon two-levels recombination theory formulae when gAu,a≠1 and gAn,d≠ 1 The ratios of the ca-culated lifetime of minority carrier to the experimental data are between 1.64 and 0.745.
A STUDY ON PHOTOLUMINESCENCE IN a-C:H FILMS
CHEN GUANG-HUA, YAN SHAO-GUANG, ZHANG FANG-QING
1992, 41 (3): 500-505. doi: 10.7498/aps.41.500
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In this paper, the changes of photoluminescence (PL) spectra according to varied measuring temperatures, annealing temperatures, and excition wavelength in a-C:H films deposited by rf glow discharge are studied. The experimental results show that the PL efficiency becomes lower with increasing the measuring temperature or annealing temperature. We give an explanation to the phenomena using the two-phase model in a-C:H system. Furthermore, the PL spectra also changes with excitation energy; and as the latter geis near the optical gap Eopt, the emission intensity reaches its maximum.
EFFECT OF ANHAMONICITY OF LAYERED TRANSVERSE-OPTICAL PHONONS ON HIGH-Tc SUPERCONDUCTIVITY
WANG HAN-TING, XIONG SHI-JIE
1992, 41 (3): 506-510. doi: 10.7498/aps.41.506
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The effect of anhamonicity of layered transverse-optical phonons on the interayer pairing is investigated by a canonical transformation from a two-level-system model. The results show that the critical temperature Tc is zero only when the difference Ω of the two levels is smaller than a critical value Ωc, and Tc increases with the decrease of Ω. It is consistent with the importance of the axial motion of the ions in the insulating sheets as has been revealed by the recent experiments.
EFFECT OF e-e INTERACTION ON THE SOLITON PAIR IN Na-DOPED TRANS-POLYACETYLENE
CUI YUN-LONG, LIN SEN-HAO, ZHANG JIA-HUA
1992, 41 (3): 511-516. doi: 10.7498/aps.41.511
Abstract +
The Hamiltonian we used includes the static SSH model, the Hubbard model and Na+ phenomenological potential in trans-polyacetylene. When the distance of the soliton pair in Na-doped trans-polyacetylene is 15α, the effect of e-e interaction within an unrestricted Har-tree-Fock scheme on the band structure of trans-polyacetylene, the charge density of the chain and the half-length of the soliton are studied.
AN IN-LINE ANALYSIS SYSTEM OF SLOW POSITRON BEAM FOR MOLECULAR BEAM EPITAXY
HE YUAN-JIN, HU YONG, DAI LUN
1992, 41 (3): 517-522. doi: 10.7498/aps.41.517
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The design and arrangement of an in-line analysis system of slow positron beam for molecular beam epitaxy is described and the analysis method using positron beam technique to study semiconductor films is introduced. In the slow positron moderator, a combination of tungsten-rings and "Venetian blind" structure are used to obtain a higher efficiency of conversion from fast to slow positrons.
ARUPS STUDY OF THE COADSORPTION OF CO AND K ON Cu(111)
BAO SHI-NING, XU RONG, LI HAI-YANG, ZHU LI, XU CHUN-YI, XU YA-BO
1992, 41 (3): 523-527. doi: 10.7498/aps.41.523
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The results of an angle resolved UPS study on K-CO coadsorbate on Cu(111) show that there is a molecular adsorption state of CO on the Cu(lll) with potassium at room temperature. The low 4σ/(5σ + 1π) intensity ratio suggests that the CO molecules inclined strongly in this state. Two adsorption states of CO are found at low temperatures (~150K). One of them appears for higher CO exposure (≥1L) only, and the other which exists for all (tcposures is similar to that at room temperature.