Search

Article

x

Vol. 43, No. 10 (1994)

1994-05-20
NUCLEAR PHYSICS
THE STUDY OF NON-RUTHERFORD BACKSCATTERING OF 4He FROM CARSON
SHEN HAO, CHENG HUAN-SHENG, TANG JIA-YONG, YANG FU-JIA
1994, 43 (10): 1569-1575. doi: 10.7498/aps.43.1569
Abstract +
The 170.0°±1.5° backscattering cross sections of 4He from C were measured in the energy range of 5.0-9.OMeV. The R-matrix was used to analyze the scattering cross sections, thus energy level parameters of the compound nucleus 16O, for alpha energies from 3.224MeV to 10.544MeV, were identified. These level parameters can be used to calculate the cross sections at certain angles according to the real experimental conditions The behaviour of a narrow strong resonance at 4.250MeV was inspected at different energy smear and scattering angles of 1650 and 1700. In the two energy regions: 3.600-4.200MeV and 6.425-6.700MeV, the cross sections exhi-bit a smoothly in creasing variation The messured and calculated cross sections show that in the energy range of 3.60-4.20MeV region, the cross sections are not significantly influenced by the scattering angle, but in the energy range of 6.425-6.700MeV region, the cross sections are strongly angle-dependent.
ATOMIC AND MOLECULAR PHYSICS
ULTRAVIOLET SPECTROSCOPIC STUDY OF EFFECTS OF CCl4,CH2Cl2 and CHCl3 ON PHOSPHATIDYCHOLINE
FENG YU-YING, YANG SONG-LING, CHEN LING-FU, WANG QIANG-HUA
1994, 43 (10): 1576-1579. doi: 10.7498/aps.43.1576
Abstract +
The effects of CCl4,CH2Cl2 and CHCl3 on the phosphatidycholine (PC) have been studied by means of ultraviolet spectroscopy. The spectra show one maximum of PC in CCl4 and two maxima of PC in CH2Cl2 and in CHCl3. The properties of the maxima of the spectra can be explained. The collective state of PC molecule in membrane can also be examined.
SIMULATION OF TWO AND THREE DIMENSIONAL RING POLYMERS USING CLOSED GAUSSIAN RANDOM WALKS
PENG JING-CUI
1994, 43 (10): 1580-1586. doi: 10.7498/aps.43.1580
Abstract +
In two dimensional systems, the non-self crossing condition leads to an excluded volume effect, and the obtained critical index,is in good agreement with the predictions of the renormalization group theory. In three dimensional systems, the condition of absence of knots should lead to new effects. However, it is observed that the probability of knot formation increases very slowly with the number of segments, and it is difficulty to find a reliable critical index. This paper makes an advancing step on this investigation.
FORMATION OF CLUSTER IONS InxP+y BY LASER ABLATION
SHI CHAO-SHU, JU XIN, TANG XIAO-WEI, ZHANG NAN, GAO ZHEN, KONG FAN-AO, ZHU QI-HE
1994, 43 (10): 1587-1592. doi: 10.7498/aps.43.1587
Abstract +
Laser ablation of indium phosphorus was investigated in tandem TOF mass spectrometer. The odd-even rule related to the P atoms was observed, the mass spectra of cluster ions exhibits a maximum when the number of P atom is odd. Theoretical calculation for InxP+y(y=1-3) with DV-Xα method indicated that the clustcr formation rule was in accordance with the conjugation energy curve. The structure of special cluster ions with "magic number" was also disscused.
CLASSICAL AREA OF PHENOMENOLOGY
RED SENSITIVITY OF DICHROMATED CELLULOSE TRIACETATE HOLOGRAPHIC MATERIAL
HE LONG-QING, WANG GUO-PING, GUO LU-RONG, CHEN QI-RUI, DAI CHAO-MING
1994, 43 (10): 1593-1597. doi: 10.7498/aps.43.1593
Abstract +
The red sensitivity of dichromated cellulose triacetate (DCCTA) holographic recording material without any dye sensitization is reported. This sensitivity is due to the absorption of the intermediate chromium (V) formed in the process of Cr6+→Cr3+. The real time transmission grating has been recorded using a He-Ne Laser as light source (632.8nm).
ENHANCING THE NUMBER-NOISE SQUEEZING OF OUTPUT LIGHT OF A LED DRIVEN BY HIGH-IMPEDANCE CONSTANT-CURRENT SOURCE USING NEGATIVE FEEDBACK
LIU JIA-REN, ZHAO BO, WANG YU-ZHU
1994, 43 (10): 1598-1604. doi: 10.7498/aps.43.1598
Abstract +
In this paper, we study the relations between the number-noise squeezing of the output light of a LED driven by high-impedance constant-current source and LED's electronic/optical quantum efficiencies, ieakage current effect, negative feedback of photon-flux fluctuation and noise frequency. We poiat out that with appropriate negative-feedback of the photon-flux fluctuation, LED driven by high-impedance constant-current can generate number-squeezed state light, the number-noise squeezing is significantly enhanced and its ideal value is limited only by residual noise of the high impedance constant-current source, LED's leakage current effect and quantum efficiency.
TRANSMISSION THEOREM OF LASER POLARIZATION
GAO ZHI-HUI, GUO SI-JI
1994, 43 (10): 1605-1614. doi: 10.7498/aps.43.1605
Abstract +
The transmission theory of laser polarization is established in the present paper. The transmission matrix of laser polarization in optical system is derived. The important theorem-the transmission theorem of laser polarization is deduced. Transmission properties of laser polarization are analysed.
DYNAMIC GAIN IN THE AMPLIFICATION OF OPTICAL SOLITON
ZHAO SHANG-HONG, XIANG DE-QUAN
1994, 43 (10): 1615-1622. doi: 10.7498/aps.43.1615
Abstract +
The self-frequency shift (SFS) resulting from Raman self-pumping effect of optical soliton and amplifer spontanious emission (ASE) noise produced in the amplification of optical soliton can both be reduced significantly by making amplifer gain depend on soliton frequency. In this paper, the above two schemes are investigated analytically and numerically by using pertubation method of inverse scattering theory and the concept of fouier transform an ensemble average. The result shows that the two schemes are effective in controlling ASE noise hence the limitation of G-H effect can be weakened obviously. The comparison with results of computer similation is made.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
A STUDY ON X-RAY SPECTRA OF NICKEL-LIKE IONS OF HIGH-Z ELEMENTS
DONG CHEN-ZHONG, ZHOU YU-QING, ZHANG BAO-HAN, YANG GUO-HONG, LEI AN-LE
1994, 43 (10): 1623-1629. doi: 10.7498/aps.43.1623
Abstract +
Soft X-ray spectra of laser-produced plasmas of highly ionied Hf,Ta,W and Re were obtained. by using a PET crystal spectrometer in the wavelength region of 5-8?,Some of resonance and inner-shell transitions of the type n=3-4 in the Ni-like isoelectronic sequence were identified. Wavelengths were measured with an uncertainty of ±0.005?. Agreement with computational results of MCDF and HFR method is excellent.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
EXAFS STUDIES OF MECHANICAL ALLOYING Fe-Cu BINARY SYSTEM
HU TIAN-DOU, YIN SHI-LONG, WEI SHI-QIANG, LIU WEN-HAN, LIU FANG-XIN, GAO CHEN, YANG YUAN-ZHENG, DONG YUAN-DA
1994, 43 (10): 1630-1637. doi: 10.7498/aps.43.1630
Abstract +
The EXAFS technique was used to study the changes of Fe and Cu atom neighbor environment following the milling time and composition of Fe-Cu system. The resutls show that the range of Fe-Cu solid solution can be greatly extended and can form nanometer sized non-equilibrium metastable alloy particles mechanical alloying. For Fe80Cu20(160h), K-edge absorption curve and radial structure function of Cu are similar to that of a-Fe powder, has the bcc structural characte-ristics, the Fe-Cu alloy particles is bcc structure also. The structure of Fe-Cu alloy in Fe60Cu40(160h) is the fcc structure, it is different from that of Fe80Cu20(160h). In nanometer sized Fe-Cu metastable alloy particles of Fe60Cu40(160h), Cu and Fe are not uniformly dispersed, Cu is a little richer in the core, but Fe is abundant on the surface.
STUDY ON THE REGULARITY OF FORMATION OF THE BINARY AMORPHOUS ALLOYS OF TRANSITION METALS BY ME-CHANICAL ALLOYING
WU LI-JUN, WAN ZHI-QI, ZHANG HENG, ZHANG BANG-WEI
1994, 43 (10): 1638-1647. doi: 10.7498/aps.43.1638
Abstract +
The regularities of formation of binary amorphous alloys of transition metals by mechanical alloying were studied successfully by the Miedema coordinates and the three chemical coondinates with the Miedema parameters, Based on egperimantal data the criteria of formation the binary amorphous alloys were defined as. The total accuracies for separating the amorphous alloys formed or not by mechanical alloying are 80% and 88%,respectively. The physics for describing the regularities for the binary amorphous alloys of transition metals by mechanical alloying, and the relationship between the regularities and necessary conditions for amor-phization by solid state reaction are discussed from the view points of interaction between atoms and thermodynamics and dynamics for amorphization by solid state reaction.
IONIC CONDUCTIVITY UNDER HIGH HYDRO-STATIC PRESSURE IN HIGH POLYMER THIN FILM (PEO)n-CuBr2
XIE BIN, SU FANG, WANG WEN-LOU, JIANG ZONG-SI, LIN FENG-LIANG
1994, 43 (10): 1648-1657. doi: 10.7498/aps.43.1648
Abstract +
WE used polyethylene oxide (molecular weight =5×106), with addition of diffcrent weight of CuBr2 (ratio n=[EO]/[Cu]= 4,8,12,16,24), to prepare a series of high polymer ionic conductor (PEO)n-CuBr2. Their complex impedance spectra in the high hydrostatic pressure range of 0.1-350 MPa and alternating conductivity in the pressure range of 0.1-2400MPa were measured. Results show that pressure dependence of conductivity can be decomposed into four saperimposed linear dependences components. According to phase analysis of X-ray diffraction curve, these straight lines respectively belong to pressure effect of amorphous phase of PEO,pressure effect of crystalline phase of PEO and pressure effect of new phase CuBr2. Hence the relation between compositiod n and activation volume, limit pressure of the three types of conductivity-pressure effect were calculated. Finally we found that by adding a small amount of plasticizers, C4H6O3, can increase elasticity of high polymer film (PEO)n-CuBr2 and enhance its ionic conductivity under high pressure one or two order of magnitude.
INVESTIGATION ON THE INTERACTION OF DISLOCATION WITH POINT DEFECTS BY STRAIN AGEING INTERNAL FRICTION OF ALUMINIUM ALLOYS
TAN QI
1994, 43 (10): 1658-1664. doi: 10.7498/aps.43.1658
Abstract +
Studies were made on the influnce of alloying content, alloying elements and deformation conditions on the internal friction behavior during strain ageing of aluminium alloys. Therefrom, a description was made on the distribution of point defects and dislocation configuration. It was pointed out that the factors controlling the recovery process of strain ageing are the mobility of solute atoms and interaction energy littween dislocations and solute atoms. A complex model including unpinning of dislocation string and dislocation-atmosphere dragging was proposed. which can describe the interaction between dislocation and point defects in the, process of strain ageing. A corresponding theoretical treatment was made to explain the exper-imental phenomena reasonably.
STABLE RELAXATION ASSOCIATED WITH LI-NEAR VISCOUS MOTION OF INTERFACE IN MULTIPHASE Al-Zn ALLOY
ZHU XIAN-FANG
1994, 43 (10): 1665-1671. doi: 10.7498/aps.43.1665
Abstract +
In the present paper, the characteristics of low frequency stable damping is studied in a multi-phase eutectiod Al-Zn alloy. The experimental results show that, within a low temperature and low strain amplititude range, the damping evidently manifests itself by linear viscous characteristics, namely, it obeys a law Q=(B/f) exp(-nH/kT ), where H is the real process activation energy, B and n(=0.21)are two experimental parameters and k is the Boltzmannc constant. A value of H=0.74eV is obtained, which is closely related to the viscosity during interface motion. Accordingly, a linear viscous interface motion model is proposed. Using this mode we can explicitly explain the experimental results.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
INSULATOR-METAL TRANSITION OF THE 2-D HALF-FILLED HUBBARD MODEL AT FINITE-TEMPERATURES
CHHN FENG, YING HE-PING, XU TIE-FENG, LI WEN-ZHU
1994, 43 (10): 1672-1676. doi: 10.7498/aps.43.1672
Abstract +
In the present paper, we attempt to attack the problem of the existence of insulator-metal transition at finite temperature for a 2 dimensional half-filled Hubbard half-filled model. we used the grand Canonical quantum Monte Carlo method to caculate the electrical conductivity and the specific heac of the system. A peak on the specific heat vs temperature curve in high temperature region is observed, and the electrical conductivity curves show a sudden rise in the same temperature region. Thus, our results support that there exists a transition.
SUBSONIC AND SUPERSONIC SOLITONS IN AN ANHARMONIC LINEAR CHAINS WITH SECOND-NEIGHBOUR INTERACTION
YU CHAO-FAN, ZHOU YI-CHANG
1994, 43 (10): 1677-1687. doi: 10.7498/aps.43.1677
Abstract +
Based on the method of coherent states, the nonlinear effects caused by the interaction between electrons and acoustic lattice vibrations in an anharmonic linear chains are investigated in the secolid-neighbour interaction approximation. While the continous limits of the equations of motion is considered self -consistently, the cubic anharmonicity of the deformable potential leads to a new nonlinear equation for the electronic orobability amolitute, which gives a new solitary solution in the form of hyperelliptic integral. This shows that besides the bell-solitons there also exists a second type of solitary excitation with the shape of a kink.
THE I-V CHARACTERISTICS OF SILVER THIN FILM ON THE RANDOM FRACTAL SUBSTRATE
WANG JING-SONG, XU YU-QING, ZHANG QI-RUI, YE GAO-XIANG
1994, 43 (10): 1688-1692. doi: 10.7498/aps.43.1688
Abstract +
The silver thin films were deposited on the substrates of the α-alumina ceramic which possess a random fractal structure. The I-V characteristics of such films exhi bit nonlinear behavior in air and a switching type voltage breakdown effect by in situ measurement in vacuum. Based on the structure geometry of the substrate, we explaine these phenomena with the developed Random Tunnelling Junction Network model.
CHARACTERISTICS OF TEMPERATURE DEPENDENCE OF CRITICAL CURRENT IN TYPICAL GRANULAR SYSTEM YBa2Cu3O7/V2O5
ZHAO YONG, ZHUGE XIANG-BIN, HE YE-YE
1994, 43 (10): 1693-1703. doi: 10.7498/aps.43.1693
Abstract +
By synthesising the (YBa2Cu3O7)1-x(V2O5)x(0c∝(1-t)n with n=1.6 without exception, this can be interpreted with the percolation of a three-dimensional network Josephson-junction system. However, for those without the two-peak transition, the n value is larger than 1.6, and distributes within a wide range. The cause for the distribution of n value are also considered and discussed.
HIGH-PRESSURE STUDIES OF THE Gd1-xCaxBa2Cu3O7-y HIGH-Tc SUPERCONDUCTORS
HAN CUI-YING, FANG FANG, XIE SI-SHEN
1994, 43 (10): 1704-1711. doi: 10.7498/aps.43.1704
Abstract +
We have investigated the superconductivity of Ca2+-dopped Gd1-xCaxBa2Cu3O7-y compounds under both ambient and high pressure. Using a Bridgman-anvil cell, the high pressure up to 9.0GPa, in temperature range of 1-300K, have been obtained. The superconducting transition temperature Tc (onset) initially increases with pressure at a rate of dTc/dP=7.68, 7.8 and 4.46K/GPa for x=0.10, 0.15, 0.20 samples at 0GPac has been investigated. By using the data of the structural parameters of samples at ambient pressure and the changes of the distances between cation and oxygen with the pressure, the role of the CuO2 plane on superconductivity is demonstrated. The coupling between the CuO2 planes may be used to explain the nonlinear dependence of Tc(P).
ANALYSIS OF BEAM PROPAGATION THROUGH THICK NONLINEAR MEDIA BY VARIATIONAL APPROACH
TIAN JIAN-GUO, ZANG WEI-PING, ZHANG GUANG-YIN
1994, 43 (10): 1712-1717. doi: 10.7498/aps.43.1712
Abstract +
By variational approach, we analyze the characteristics of beam propagation through a cubic nonlinear optical medium, and obtain the analytic solution to the normalized transmittance at the center of far-field as a function of sample position. We also analyze the peak-valley transmittance change and peak-valley transmittance separation as a function of sample length, and results are basically consistent with previous experimental results.
REFLECTANCE SPECTRUM AND OPTICAL PROPERTIES OF NANO-wBN IN THE VUV REGION OF SYNCHROTRON RADIATION
CHI YUAN-BIN, HAN ZHENG一FU, SHI JUN-YAN, JU XIN, SU YI-XI, WEI KUN, DENG JIE, SHI CHAO-SHU
1994, 43 (10): 1718-1725. doi: 10.7498/aps.43.1718
Abstract +
The reflectance spectrum of different wBN was measured. The sample were prepared by shock-wave method and heat-treated at 100℃ and 500℃. The measurement was performed in the wavelength range of 100-240nm at the time-resolved spectroscopy station of National Synchrotron Radiation Laboratory in Hefei. The optical constants of wBN have been determined in the VUV region by applying the Kramers-Kronig relation to normal incidence reflectance data. It was found that the average value of optical band gap determined from these constants is 8.7±0.5eV. The dielectric constants, optical conductivity of wBN were also obtained. The effet of the charges of particle size and structure of the nanometer-sized wBN on the optical reflectance spectrum were further studied.
COLLISION CASCADES INDUCED BY LOW ENERGY CLUSTERS IMPACTING ON METALLIC THIN FILMS (II)——THE ACCELERATION OF CLUSTER ATOMS
PAN ZHENG-YING, LI RONG-WU
1994, 43 (10): 1726-1733. doi: 10.7498/aps.43.1726
Abstract +
This paper present the investigation on collision cascades induced by gold clusters at 1keV/atom and aluminum clusters at 0.2keV/atom impacting on gold thin films. The energy spectra of projectiles at different time are calculated by molecular dynamics simulations. It is shown that the cluster atoms may even be accelerated during the slowing down process. The maximum energy of cluster atoms is found to be higher than their initial energy. In order to understand the acceleration mechanism, multiple collision processes have been studied. The possible energy gains of a cluster atom after double scatterings are calculated by the classical conservation laws.
EFFECT OF CRYSTAL ORIENTATION AND INCIDENT ION FLUENCE ON SPUTTERING FROM ION-IRRADIATED BaF2
SHEN DING-ZHONG, YUAN XIANG-LONG, HUA SU-KUN, ZHOU ZU-YAO, TAO ZHEN-LAN, WANG ZHEN-XIA, ZHU FU-YING, ZHANG JI-PING, PAN JI-SHENG
1994, 43 (10): 1734-1738. doi: 10.7498/aps.43.1734
Abstract +
BaF2 Crystal was irradiated with 27keV Ar+ ions along the normal of (111), (100) and (110) planes at a current density of 1017μA/cm2. Using collector technique and RBS analysis, the angular distribution and yield of Ba atoms sputtered from BaF2 crystal have been measured as a fuction of orientation and ion fluence. The obtained angular distributions of Ba atoms sputtered are over-cosine type for all specimens. The sputtering yields were strongly dependent on the fluence of the incident beam on the targets
STUDY ON THE SYNTHESIS AND PHASE TRANSITION OF LaxBi2-xTi4O11
MENG JUN-FANG, ZOU GUANG-TIAN, CUI QI-LIANG, ZHAO YONG-NIAN
1994, 43 (10): 1739-1744. doi: 10.7498/aps.43.1739
Abstract +
The system LaxBi2-xTi4O11 has been synthesised, their Raman spectra and powder X ray diffraction pattern as well as the high temperature Raman spectra of La0.2Bi1.8Ti4O11 have been measured. The results show that the phase transition at x=1.2 occurring in LaxBi2-xTi4O11 is correlated with the lowest frequency phonon mode. The Phase transition temperature of La0.2Bi1.8Ti4O11 is 200℃. The structure of La2Ti4O11 can be considered as an orthorhombic one.