Vol. 38, No. 8 (1989)
1989, 38 (8): 1215-1224.
A new kind of oscillator configuration of free electron laser, the free electron cyclotron resonance laser is proposed and analyzed. The expressions for electron efficiency and startup current are given.
1989, 38 (8): 1225-1234.
Starting from population density matrix equations, five kinds of nearresonant enhaneed three-photon eleetronic transitions in the interaetion between differently polarized laser fields and molecules with casecade four-level strueture and folding four-level structure are discussed respectively. And ,taking the third transition as the probe signal, the relative intensities and the characteristic of the signals are derived analytically. The line-shape factors and intensity factors of the relative intensities are greater by different degrees when compared with the of three-level molecules.Therefore the relative intensities of the probe signal may be greater by several orders. The Potential applications of these results in moleeular speetroscopic analysis are also diseussed.
1989, 38 (8): 1235-1244.
The steady and transient characteristic of lateral photovoltaic effect in a-Si:H juncitions have been explored by theoretical analysis. The results show that the theoretical predictions are in good agreement with the experiments .It 1is worthy to note that two important parameters of the sample (i,e.the sheet resistance l/as of a-Si:H and the transit time T_m) evaluated according the theoretical relations with the conventional accepted mobility and conductivity of undoped a-Si:H are much larger than that deduced from the experimental data .Based on this with a reasonable analysis, we suggest that electrons in a-Si:H layer may transport parallel to the junction with a surprisingly high mobiliry.
1989, 38 (8): 1259-1264.
Comparing the transmission spectra with the electron micrographs and Raman spectra of metal ions-silver sol systems, we summarized the general relations between the aggregation state of silver sol with surface enhancement factor.
1989, 38 (8): 1271-1279.
The correlation factor u(R) m the quasi two dimensional system—the inversion layer is obtained with the effective interaction potential V_eff_(R) and the collective oscillation behavior of the electron gas. The pair correlation function the correlation energy and the many-body wave function have been calculated on the basis of the CBF theory.
PHASE TRANSITION IN SOME FERROELECTRIC NIOBATE CRYSTALS WITH TUNGSTEN BRONZE STRUCTURE AT LOW TEMPERATURES
1989, 38 (8): 1280-1289.
Dielectric and pyroelectric properties have been measured in six ferroelectric niabate single crystals with tungsten bronze structure from 15K to room temperature. The dielectric and pyroelectric results showed that, in all the three kinds of ferroelectric niobate single crystals SBN , PBN, KNSBN with TTB structure, a new phase transition occurred between 50K and 70K, which were further supported by the X-ray experiment. The crystals symmetry changes from point group 4mm to point group mm**2,and the direction of ferroelectric polar-axis changes from the c-axis of tetragonal lattice cell to the b-axis of orghogonal lattice cell as the temperature drops. The difference between high frequency dielectric constants and low frequency dielectric constants indicates that the phase transition possesses diffuse character. According to the specific heat measurement, it is confirmed that this phase transition is a higher order transition. A model of structural change has been proposed to explain this phase transition.
1989, 38 (8): 1290-1298.
Internal friction of mono-and poly-crystal pure aluminum during creep at about 1Hz was studied. It was observed in monocrystal specimens that the internal friction decreased monotonously in the early stage of creep. A significant creep time-internal friction (1/Q-t) peak was observed during the latter half of the primary creep under suitable experimental conditions. And the internal friction kept constant during the secondary。But no 1/Q-t peak was observed with polycrystal sample under similar experimental conditions .We suggest that the appearance of 1/Q-t peak is due to the increase of the damping coefficient of moving dislocations during primary creep .A specific dislocation mechanism is proposed, and the expression thereby deduced for the internal friction during creep is satisfactorily consistent with the experiments.
1989, 38 (8): 1322-1328.
We obtained the time dependence of the transverse profile, veloeity and energy of longitudinal solitary waves in an elastic rod , in the case for which the viscoelastical damping is small but cannot be neglected ,by using the method of perturbation. The results showed that owing to the presence of viscoelastical damping, the height and velocity of solitary wave diminish, while the width increases with time and the energy dissipates gradually until it disappears.
1989, 38 (8): 1329-1333.
A new method to obtain concentration-dependent diffusion coefficient the method of approximation is developed. By applying the approximation method, we overcome some difficulties encountered in using Boltzmann-Matano method, ,and are able to calculate concentration-dependent diffusion coefficient as accurately as we want. The approximation method is proved to be valid both theoretically and practically.
1989, 38 (8): 1334-1338.
Fractal growth in different systems is discussed primarily in this paper. By analyzing the transmission spectra of many kinds of fractal in different systems, we found that the position of the new absorption band in the transmission spectrum was proportional to logarithmic time. Furthermore we found that the whole curve of position of new absorption band as function of logarithmic time could be divided into two straight parts. This shows that while the fractal growth proceeds, there are mainly two different processes according to the fractal speed.
1989, 38 (8): 1339-1343.
We have studied the energy spectra and the electronic states of Bi-polaron in cis-(CH)_x_ with SSH-Hubbard model by using a selfconsistent approach. Four new localized electronic states are discovered. They form four discrete levels outside the conduction and valence bands: two locates near the bottom and the top of the conduction band, the other two near the valence band. The e-h symmetry is destroyed by the e-e interaction. And these localized electronic states vary with the coupling constant and the Hubbard e-e interaction parameter U.
1989, 38 (8): 1344-1347.
Slip dislocation in In-doped and undoped GaAs singe crystal were investigated by means of X-ray topography. Different configurations of the slip dislocations were observed, which resulted from the different densities of dislocations. The mechanism of the slip dislocations and cellular network structure formation is also discussed preliminarily.
X-RAY STUDY ON THE CRYSTALLOGRAPHIC CHARACTER-IZATION OF FERROELECTRIC CERAMICS:Na_0.5_Bi_0.5_TiO_3 AND ITS SOLID SOLUTION SYSTEM
1989, 38 (8): 1348-1353.
The Na_0.5_Bi_0.5_TiO_3-BaTIO_3_ system, at certain composition range, is a new kind of uItrasonic transducer ceramics material which has good and unique properties. By means of X-ray powder diffraction method, we precisely determined the cell parameters of Na_0.5_Bi_0.5_TiO_3, and propose a new type of Iattice structure for it different from that in previous reports. For this system, the Iattice Parameters at different compositions were determined. And the preliminary discussions on the relations between the properties, cell dimensions and compositions as well as the phase relation were also given.
DIFFUSION OF ELEMENTS AND FORMATION OF INTERME-TALLIC PHASE AT THE INTERFACE OF THE BINARY DIFFUSION COUPLES
1989, 38 (8): 1354-1359.
Based on the data of element diffusion, formation heat of phases and their stabilities, we analysed the element diffusion at the interface of a binary diffusion couple and the formation of intermetallic phases. The results of experimental investigation for Ti-Ni, Nb-Sn and Ta-Pt system are presented.
PHONON一MEDIATED SPECIFIC TRAPPING RATE OF POSITRONS TO THE SHALLOW ENERGY LEVEL OF A SMALL VACANCY CLUSTER
1989, 38 (8): 1360-1363.
If there is a trapped state of a positron with binding energy lower than Debye energy at a small vacancy cluster, the capture of positrons from free state to this level will be strong temperature dependent . There are two kinds of the dependences and the specific trapping rate may be quite high, which shows great differences between small vacancy clusters and dislocations.
1989, 38 (8): 1369-1374.
A series of experimental facts for LnBa_2_Cu_3_O_7-y_ single crystals indicate that imperfect structure and non-uniformity composition in samples have an important effect on their normal state resistivity, normal-superconductive transition behavior, T。and critical current and so forth. We think that in imperfect single crystals, there also exist superconductive glass state effects, similar to single phase polycrystal LnBa_2_Cu_3_O_7-y_ samples.
1989, 38 (8): 1375-1378.
In this paper, we construct a super-Beltrami algebra. It is related to the super-quasicon-formal transformation on super-Riemann surfaces and contains two super-conformal (NSR) slgebras as subalgebras. In this paper, we construct a super-Beltrami algebra. It is related to the super-quasicon-formal transformation on super-Riemann surfaces and contains two super-conformal (NSR) slgebras as subalgebras.
1989, 38 (8): 1379-1383.
Tungsten-silicon films were deposited on oxidized silicon wafers by direct current magnetron Co-sputtering from a W-Si mixture target. Films were then rapid thermal annealed in vacuum at temperature between 500 and 1000℃ for 15s. The sheet resistance of W-Si films as a function of the annealing temperature shows an anomalous maximum. This phenomenon has been studied by using XRD. We observed that there were W_5_Si_3_ appeared in the annealed film at temperature up to 1100℃, which contributed partly to the sheet resistance.
1989, 38 (8): 1384-1390.
In this paper, we generalize two theorems in General Relativity. The symmetry in the conditions for the theorems is relaxed to conformal symmetry. The generalized theorems read as follows: 1. Any conformally spherically symmetric electro-vacuum solution to Einstein equations must be the Reissner-Nordstrom solution. 2. Any conformally plane-symmetric electro-vacuum solution to Einstein equations must be the Kar solution.