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Vol. 32, No. 7 (1983)

1983-04-05
CONTENT
THE NUTATION AND RELAXATION ASSOCIATED WITH THE HFS 0-0 TRANSITION OF THE Rb87 GROUND STATE
TANG CHANG-GUO, DONG TAI-QIAN, ZHENG LE-MIN
1983, 32 (7): 829-837. doi: 10.7498/aps.32.829
Abstract +
The nutation and relaxation signal associated with the hfs 0-0 transition of the Rb87 ground state are calculated and observed. The experimental results are qualitatively in agreement with the calculation.
TEMPERATURE DEPENDENCE OF RETROGRADE VELOCITY OF VACUUM ARCS IN MAGNETIC FIELDS
FANG DAO-YU
1983, 32 (7): 838-844. doi: 10.7498/aps.32.838
Abstract +
Using optical method the retrograde velocities of vacuum arcs in magnetic fields were measured as a function of the cathode temperature for Cu, Al and 316 stainless steel used as the cathode material. It was found that with increasing the cathode temperature the arc velocity decreases. The experimentally measured temperature dependence of retrograde velocity of vacuum arcs can be explained by the ion jet model for retrograde motion of vacuum arcs.
EXPERIMENTS ON DIRECTOR WAVE IN NEMATIC LIQUID CRYSTAL
ZHU GUO-ZHEN, NI HUI, ZHANG WEN-ZHU
1983, 32 (7): 845-853. doi: 10.7498/aps.32.845
Abstract +
In a homotropic nematic cell, a solitary-like director wave is excited by a mechanical method. A series of photographs of the wave propagation process are obtained. When white light is used, we noticed the propagation of some dark lines along the cell, and we got the plot of the positions and velocities of the dark lines vs time. According to the results obtained from the interference patterns of focused polarized light, it was shown that the dark lines correspond to a perpendicular alignment state of the director, in addition, the scattered light by liquid crystal is observed clearly on the two sides of dark lines. From the wave propagation process recorded by monochromatic light, and by using an one dimension postulat, we calculated the spatial distribution of the directors. Finally, some discussion on the physical model of the director wave is given.
THE STUDY OF VIBRATIONAL ENERGY TRANSFER DYNAMICS IN BCl3 EXCITED BY AN INTENSE INFRARED FIELD
FU GUANG-SHENG, WU ZHEN-QIU, XU JI-REN, HUANG NAN-TANG, JIANG YI-FENG
1983, 32 (7): 854-866. doi: 10.7498/aps.32.854
Abstract +
On the basis of ref. [1], the time-resolved absorption spectrum of vibrational excited states v3 in BCl3 molecules are observed and investigated in higher laser energy flux. The excitation of vibrational states and a variety of energy transfer processes in relaxation, as well as their dependence on the pumping laser energy, the pressure of BCl3 and other parameters are measured. The result shows that there exists an ensemble of nonthermal distribution in vibrational states and the rotational energy transfer plays an important role in generating this nonthermal distribution. The processes of development of the BCl3 vi-bratioal excited absorption spectrum are discussed by using a simplified dynamical collision model. A simple relation Prv-v= c/K′(Tv,T<0,q) for the redistribution of the vibrational states and the analytical expressions for the equivalent vibrational temperature and the average number of the absorbed photons are obtained. They are qualitatively in agreement with experimental results.
ENERGY TRANSFER OF THE EXCITON IN THE QUASI-ONE-DIMENSIONAL ANTIFERROMAGNET CsMnCl3·2D2O
YAN. W. M., JIA WEI-YI
1983, 32 (7): 867-874. doi: 10.7498/aps.32.867
Abstract +
The dynamic processes, of energy transfer of the 4T1 exciton of Mn2+ ions have been studied in the temperature region 2-300 K in the pure and Mg2+-, Ni2+-, Co2+-doped quasi-one-dimensional antiferromagnet CsMnCl3·2D2O (CMC). It has been found that the fluorescent intensity and the lifetime of the exciton drops rapidly with increasing temperature in the region 2-10 K, with a further weakened fluorescence and shortened lifetime in the heavily doped crystals. These phenomena are presumed to be associated with the multiphonon nonradiative transition and energy transfer between donors and acceptors, both of which are related to the magnetic interactions and the spin ordering. At higher temperature, the rate of energy transfer increases. However, because of the persistence of spin short-range order and the Jahn-Teller effect, the energy transfer among donors is still limited to some extent, and nonexponential attenuation processes appear. The different impurities show different abilities of trapping and relaxing to a certain degree.
THE GROUND STATE ENERGY OF ISING SPIN S=1 MODEL OF A FCC LATTICE ANTIFERROMAGNETICS WITH NEXT NEAREST NEIGHBORS INTERACTION IN A MAGNETIC FIELD
WANG YANG-PO
1983, 32 (7): 875-887. doi: 10.7498/aps.32.875
Abstract +
As an extension of the method presented in reference [4], this paper concerns with the transformation from Ising spin S=1 systems to a Fermion system in which the total number of particles is not a constant. We obtained rigorously the ground state energy of the antiferromagnetics of Ising S=1 fcc lattice with nearest neighbors and next nearest neighbors interaction in an arbitrary magnetic field, and also the phase equilibrium diagram at T = OK.
THEORETICAL EXPLANATION OF THE LIGHT DIFFRACTION DUE TO SPACE CHARGE FLUCTUATION IN THE QUASI ONE-DIMENSIONAL IONIC CONDUCTOR-α-LiIO3 (I)——ANISOTROPIC MODES
GU SHI-JIE, LI YIN-YUAN
1983, 32 (7): 888-899. doi: 10.7498/aps.32.888
Abstract +
A theoretical treatment was developed to explain the light diffraction bands normal to the c-axis subtending large angle and strong in intensity which were investigated in much details with a -LiIO3 single crystals under the action of a d. c. field. It is assumed only that a fluctuation of the space charge density Sp (x, y) appears as ionic transportation taking place in the c-direction. The related internal field sE (x, y) produces δεij (x, y) for the dielectric tensor through the linear electro-optic effect. As a consequence, anisotropic phase gratings come into existence in the crystal. With such a model we successfully explained quantitatively or qualitatively all observed phenomena such as the polarization of diffracted beams turning π/2, the angular distribution of diffracted intensity being asymmetric and possessing a minimum, and those observed using specimens of different absolute configurations being related as mirror images. The relative positions of the diffracted bands and their shapes observed with specimens cut in different orientations with respect to the c-axis were found in agreement with our theoretical derivation. The variation of the angular position of the minimum intensity with the change of the incident angle were calculated and satisfactory results were obtained. Therewith we evaluated for the first time the ratio of two elements of the electro-optic tensor γ42/γ41=1.6 in a d. c. field.
THEORETICAL EXPLANATION OF THE LIGHT DIFFRACTION DUE TO SPACE CHARGE FLUCTUATION IN THE QUASI ONE-DIMENSIONAL IONIC CONDUCTOR-α-LiIO3 (II)——ISOTROPIC MODES
GU SHI-JIE, LI YIN-YUAN
1983, 32 (7): 900-910. doi: 10.7498/aps.32.900
Abstract +
In ref.[1] a theory has been formulated for treating the anisotropic modes (o→e) of diffraction observed in α-LiIO3 single crystals under a d. c. field. In the present article we consider the isotropic modes (o -o, e e) of diffraction observed in similar conditions with the same material. There are two kinds of diffraction bands: (1) those perpendicular to the c-axis and wide in angular extension, and (2) those inclined to the c-axis and limited in angular extension. For the former, our theoretical derivation yields the experimental findings that with the incident beam normal to the c-axis only very weak o → o and e →e bands may appear, while the o → o band remains weak but the intensity of the e → e band multiples as the angle between the incident beam and the c-axis decreases from π/2. For the latter, we took into account the grating effect of growth layers of the crystal enhanced by the enrichment of space charge. From the angular extension of an inclined band is about 8°, we estimated the deviation in parallelism between growth layers being no more than 2?and their average spacing about or larger than 5 μm. We also explained the diffraction spots reported in ref.[4]. The theory were given in a version more general than that in ref.[1].
STUDIES OF HYDROGEN ADSORPTION ON Al(111) AND Ag(111) SURFACES BY EHT METHOD
XU YONG-NIAN, ZHANG KAI-MING
1983, 32 (7): 911-916. doi: 10.7498/aps.32.911
Abstract +
The hydrogen adsorption on Al(111) and Ag(111) surfaces have been studied by the charge self-consistent EHT method. It is shown that the H2 molecule would dissociated on Al(111) surface, the H atom could be adsorbed at certain sites with symmetric geometry (such as the threefold, eclipsed, bridge and the atop sites), and H could penetrate into the surface layer and become an interstitial atom. However it is shown that the H2 molecule can be adsorbed on Ag(111) surface with H-H bond paralled to the surface, this result seems to be in fairly good agreement with the result of high resolution electron-energy-loss spectra for H2 on Ag at low temperature. In addition, when the temperature is high, the dissociative adsorption of H2 on Ag(111) surface is also possible.The merit of the method used is discussed.
A STATISTICAL THEORY OF THE TWO-DIMENSIONAL ALTERNATIVE BINARY SYSTEM
DU YI-JING, YAN ZU-TONG, CHEN LI-RONG
1983, 32 (7): 917-924. doi: 10.7498/aps.32.917
Abstract +
The two-dimensional alternative binary system is studied by using the Collins model. The free energy of the system is calculated. The equation of the solubility curve is given. Using the condition of phase equilibrium, the phase diagrams of the two-dimensional alternative binary system are obtained, Finally, a dicussion on the results are presented.
BRIEF REPORT
ION RANGE PARAMETERS IN BINARY COMPOUNDS WITH POSITIVE DEVIATION FROM BRAGG RULE
WANG DE-NING, WANG WEI-YUAN
1983, 32 (7): 925-932. doi: 10.7498/aps.32.925
Abstract +
In this work, we investigated the ion range parameters for binary compounds having positive deviation from Bragg rule, that is the calculated Se(E) value is higher than experimental Se(E) value, By introducing a "biatomic model" with the idea of "regular", the implanted range in binary compounds was considered not only as the stopping power of ions by two alike cofposed atoms S11(E) and S22(E), but also as the stopping power of ions by two unlike composed atoms S12(E) and S21 (E). Based on Berthelot relation, let S12(E)=S21(E)=(S11(E)·S22(E))1/2, the stopping power and total range in binary compounds were derived as follows: NS(E)=1/2[(N1S11(E))1/2+(N2S22(E)1/2)]2, R=4/a[x-A1(arctg(2x+f)/△1/2-arctg(f/△1/2))-B1(ln(x+g)2/g2·e/(x2+fx+e)) -b/2 ln(x2+fx+e/e) where X=E1/2 ,E is the ion implanted energy, all the others are constants depend upon the mass and the atomic number of the ions and targets. Combined with the relationships between R and Rp, Rp and △Rp in ref. [1], we calculated the Rp and △ Rp values in systems with positive deviation. The significances of formulas given in this paper were discussed.
PHASE DIAGRAM OF THE Dy-Sn BINARY SYSTEM
CHEN RONG-ZHEN, ZHENG JIAN-XUAN
1983, 32 (7): 933-938. doi: 10.7498/aps.32.933
Abstract +
A phase diagram of the alloys of the Dy-Sn binary system has been investigated by means of X-ray diffraction method and differential thermal analysis. The intermetallic com- pounds DySn2,Dy5Sn3,Dy5Sn4 and Dy11Sn10 were detected, and the new intermetallic Compounds Dy2Sn,DySn,Dy8Sn9,Dy4Sn7 and DySn4 were observed.There are four eutectic reactions and six peritectic reactions in Dy-Sn system. Dy2Sn,DySn,Dy4Sn7 melt congruently at 1237℃, 1222℃ and 1154℃ respectively, and Dy5Sn3,Dy5Sn4,Dy11Sn10,Dy8Sn9,DySn2 and DySn4 decompose at peritectic reaction temperatures 1140℃, 1160℃, 1175℃, 1134℃, 738℃ and 442℃ respectively. There exists a Crystal melting transformation at 1182℃ in Dy-rich region.DySn4 does not show any detectable Solid solubility in Sn and Sn shows solid solubility up 5 wt% to in α-Dy and 7 wt% in β-Dy.
THE HEXAGONAL METASTABLE PHASE FORMED IN AN AMORPHOUS Ni-P ALLOY DURING CRYSTALLIZATION (II)——TWIN GROWTH RELATIONSHIP
GUO KE-XIN, WU YU-KUN, LIANG JIN-ZHONG, CHANG XIN
1983, 32 (7): 939-946. doi: 10.7498/aps.32.939
Abstract +
The hexagonal metastable phase formed in an amophous Ni-P alloy during crystallization exhibits four different orientations. It is shown by SAD that they are four-fold rotation twins around [021]. These four crystals have a common fcc sublattice and their twin relationship may be described by a rotation of 90o about one of the axes of the sublattice.
MOSSBAUER STUDY OF Fe-Ni INVAR ALLOY
YU EN-HUA, SUN SHAO-ZHOU, JIN MING-ZHI
1983, 32 (7): 947-953. doi: 10.7498/aps.32.947
Abstract +
In this paper, the magnetic behaviour of Fe-Ni invar alloy is analysed on the basis of Mossbauer spectrum. The coexistence of two magnetic states of iron atom is revealed and invar mechanism of Fe-Ni invar alloys is interpreted according to the above view point. The equations with which one can determine experimentally the magnetic moments of the iron atom in two magnetic states are presented. Anomalous phenomena of Fe-Ni alloy at about 32 wt% Ni are observed.
THE SOLITON INDUCED BY THE FILAMENTARY PERTURBATION ON A FAST ELECTRON BEAM
HE KAI-FEN
1983, 32 (7): 954-959. doi: 10.7498/aps.32.954
Abstract +
The soliton induced by filamentary perturbation is discussed by using the reductive perturbation method. A K-dV equation for the perturbation of beam electrons is derived.
THE PERIOD-DOUBLING BIFURCATION SEQUENCES OF THE TRIMOLECULAR MODEL WITH FORCED OSCILLATION TERM
WANG GUANG-RUI
1983, 32 (7): 960-972. doi: 10.7498/aps.32.960
Abstract +
In this paper, we discuss the trimolecular model with a forced oscillation term. We carried out the numerical calculations. Some results are given for the case of forced oscillation amplitude c=0.05 and forced oscillation frequencies D over a certain range. We have found the 2n-point periodic sequences by analyzing these results and cam-pared them with Peigenbaum constant δ .