Vol. 41, No. 10 (1992)
1992, 41 (10): 1561-1566. doi: 10.7498/aps.41.1561
In this paper, by means of B?cklund transformation of generalized KP equation, sditon-like Solutions of generalized kdV equation with external force term are obtained
1992, 41 (10): 1567-1574. doi: 10.7498/aps.41.1567
The result of studies on the infrared spectra of PrxY1-xBa2Cu3O7-δ system superconductors are reported. It is found that the direct result of increasing the Pr content is that most reflectance features become stronger in the whole energy range (including midle infrared and far infrared). The fingureprint phonon of Y atom at 190cm-1 does not shift when the content of Pr changes. This confirm, that the valence of Pr in this system is greater than +3, which is the valence value of Y in YBa2Cu3O7-δ, and should be between +3 and +4. We also found that, after making the assignment of all phonons, the vibration modes whose strengths increase when the content of Pr increases must be the vibration modes in the CuO2 plane or parallel to the CuO2 plane. This case is much similar to the situ ation of decreasing oxygen content in the YBa2Cu3O7-δ system. It is showed that these vibrations in the CuO2 plane are important for the high-Tc superconduccivity.
ATOMIC AND MOLECULAR PHYSICS
1992, 41 (10): 1575-1581. doi: 10.7498/aps.41.1575
The process of releasing hydrogen from nickel foil permeated with hydrogen is investigated by XRD and a laboratory EXAFS equipment which is attached on a X-ray spectrometer. The results obtained by these two methods show that the phase content of NiH decrease exponentially in this process We also determine a definite atomic ratio of Ni and H in NiH phase and point out the location of hydrogen in the lattice. This laboratory. EXAFS equipment is proved to be suitable for the study of this kind of problem.
In DC discharge of CCl2 vapor, the emission spectrum from 520 to 630 nm has been observed and identified as the A→X transition of CC12 radical. About 400 bands were assigned to (v1′,v2′,0)→(v1″,v2″,0) progressions of 35Cl-C-35Cl and 35Cl-C-37Cl, and tabulated to Deslandres tables. Spectral analysis gave out the vibrational frequencies v1, v2 and their isotopic shifts in which the data of gas-phase CCl2 in ground state were not found yet in literatures.
CLASSICAL AREA OF PHENOMENOLOGY
1992, 41 (10): 1590-1597. doi: 10.7498/aps.41.1590
In this work, we have respectively investigated two-photon processes of a cascade three-level atom interacting with thermal and vacuum radiation fields by means of non-relativestic QED. We verified the important role of atomic thermal loss and two-photon transtion loss in the disspation processes. We proved the condition under which the thermal fluctuation can be neglected, and discussed, the character of laser cavity in which the two-photon laser can be produced.
1992, 41 (10): 1598-1604. doi: 10.7498/aps.41.1598
We investigate the temporal aspects of absorptive two-photon optical bistability described by a semiclassical theory in the limit of a fully developed hysteresis cycle and when all decay rates have comparable magnitude. We show by multiple time-scale perturbation analysis that near the high-transmission branch the behavior of the system is governed by an equation for the field amplitude which determines the long-time evolution of the system, whereas, near the low-transmission branch all dynamical variables vary on the long time scale, and it is possible to describe the transition between the two stable branch by simple equations.
A kinetics model including five levels is presented according to the emission spectrum of Cu atom observed from a CuBr laser plasma. The numerically calculated laser power, peak time and weveform, by employing the experimental data of electron temperature and density, well conform to our measurement. At fixed input power, it is also shown that to change the difusion coefficient of the buffer gas will change the average temperature of the gas or the initial density of Cu atom, therefore, change the laser power as well.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
CAVITON FORMATION AND SECOND HARMONIC EMISSION DURING THE INTERACTION OF MICROWAVE WITH INHOMOGENEOUS PLASMA
1992, 41 (10): 1613-1619. doi: 10.7498/aps.41.1613
The experimental simulations of laser-plasma interaction process by means of the microwave-plasma interaction have been performed in a steady state plasma device. The evolution of cavitom in the nonlinear interaction is experimentally investigated. The good agreement between experimental results and numerical calculation of Zakharov equation is obtained. The second harmonic emission spectrum is measured, and the mechanism of red-shift of second harmonic frequency is discussed.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
A STUDY ON BOND STRUCTURE OF NANOMETER-SIZED AMORPHOUS SILICON NITRIDE SOLIDS IN TERMS OF X-RAY RADIAL DISTRIBUTION FUNCTIONS
1992, 41 (10): 1620-1626. doi: 10.7498/aps.41.1620
The microstructure and bond character of the nanometer-sized amorphous silicon nitride solid (NANO-SNS), heat-treated in the temperature range of 25°-1000℃, were studied in terms of X-ray radial distribution functions. It was observed that the interfaces with a large volume fraction were not the "gas-like" structure but the short-range order structure, which is different from that inside the amorphous nanoparticle. Both Si-N bond length and coordination numbers of the first nearest neighbours(CN) in interfaces are less than that in traditional Si3N4 and there exist a large number of Si dangling and unsat-urated bonds. NANO-SNS has an nonty-pical covalent structure that contains lots of unsaturated and dangling bonds. This bond structure is different from the saturated covalent bond structure of traditional Si3N4.Due to the unsaturated character of the bond coordination numbers, the molecular form of NANO-SNS should be written as Si3-xN4-y. The appearence of strong polarity of NANO-SNS is closely related to unsaturated and dangling bonds.
1992, 41 (10): 1627-1631. doi: 10.7498/aps.41.1627
The whirlpool structure have been observted in HREM investigation of Si : H films deposited by glow discharge and SiC ultrafine powder synthesized by thermal chemical vapor reaction method. In this structure, strong planes are arranged around its nuclei and this seems to be whirlpools in HREM image. In this article, the cheracters of whirlpool structure are described, its forming reason and the condition under which it can be retained are analysed, and the dependence of it on microcrystal nucleation and growth processes are discussed.
1992, 41 (10): 1632-1637. doi: 10.7498/aps.41.1632
The stacking-faults are placed in a supercell which is repeated periodically. By choosing the supercell large enough, so that faults in neighboring cells do not interact much, the energy of one stacking fault may then be calculated. A first principle method (Augmented Spherical Wave Method) is used to calculate the energies of the intrinsic and extrinsic stacking faults in aluminium. The values found are ΓISF=154erg/cm2 and ΓESF=138erg/cm2 respectively. The results are quite reasonable as compared with experimental data.
1992, 41 (10): 1638-1646. doi: 10.7498/aps.41.1638
Symmetric cubic Duffing's equation can be identified to three-parameter equation by using scaling transformation. Duffing's equation with, negative linear term has a closed bifurcation region under weak periodic force, the bifurcation areas contract with increasing the linear coefficient. The equation has a set of self-similar bifurcation regions under strong periodic force. The scaling property of this regions is found and discussed in terms of a one-dimensional map, the theoretical result is in good agreement with the computational result.
1992, 41 (10): 1647-1651. doi: 10.7498/aps.41.1647
The expression of critical exponents in wetting transition at two-phase and three-phase coex-istence in Sullivan mixture are studied, It is found that the critical exponents depend neither on the model parameters not on the symmetry of dynamical potential, i. e.: the exponents have universality.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
1992, 41 (10): 1652-1660. doi: 10.7498/aps.41.1652
Using the extended real-space renormalizaation-group approach, we study the local electr-onic properties of a class of one-dimensional quasicrystals (the generalized Fibonacci chains) in the framework of tight-binding model. These quasiperiodic systems are termed the An chains, which are associated with the sequences generated by the inflation rule (A, B)→(AnB, A). We introduce 2n2+1 transformations for calculating the local electronic Green's function and the local electronic density of state at any site in any one of An chains for the diagonal, offdiago-nal and combined models. It is shown that this approach is effective and the local electronic density of states is critical, just as that of Fibonacci quasicrystal.
1992, 41 (10): 1661-1665. doi: 10.7498/aps.41.1661
The electronic structure of the one-dimensonal nanometer solid state model is discussed in terms of the grain size and the disordered degree of the grain surface by the computation of the density of electronic states. The result shows that the effect of the grained size on the electronic structure is great, and the disordered degree of the trained surface cause mainly the change of the energy width and the magnitude of the density of state.
1992, 41 (10): 1666-1671. doi: 10.7498/aps.41.1666
The distribution of electronic localisetion n the disordered system of 2000 particles is obtained by a new method for calculating eigenvector. The distribution is discussed with the density of states and the calculation error. The result shows that the distribution is changed with the energy, the distribution area may cover the entire system, and the distribution is affected by the disorder degree.
THEORETICAL CALCULATION OF QUANTUM EFFICIENCY FOR FIELD-ASSISTED InP/InGaAsP SEMICONDUCTOR PHOTOCATHODES
1992, 41 (10): 1672-1678. doi: 10.7498/aps.41.1672
The factors determining quantum efficiency of field-assisted InP/InGaAsP semiconductor photocathodes have been analysed in detail in the paper. The transmission process of electrons in the absorption layer and transferred-electron process in the emission layer as well as the escape probability of electrons in the surface of emission layer have been calculated quantitatively on the basis of continuity equations and tunnelling effect of quantum mechanics. The curves of quantum efficiency versus wavelength for various biases have been obtained. The results show that the quantum efficiency of semiconductor photocathode in the range 0.9-1.25μm can be risen two orders of magnitude or more under a proper bias. It is helpful in designing the structure of semiconductor photocathodes and choose the optimum conditions of operation.
INVESTIGATION OF THERMAL CONDUCTANCE ON BOLOMETRIC INFRARED DETECTOR OF HI GH Tc SUPERCONDUCTING FILM GROWN ON MULTILAYER SUBSTRATE
1992, 41 (10): 1679-1985. doi: 10.7498/aps.41.1679
In this paper, we set up the model of Gaussian distribution on the temperature of illuminated superconducting film and derive a serial formula, from which the equation of the substrate thermal conductance G3= 2πks· d · y(a(t),b(t),r) can be obtained. It can be used not only for G of single-layer substrate, but also for G of multi-layer substrate. The calculated results are in good agreement with the experimental ones.Using Maths CAD programm, the relations between illumination radius r, substrate thickness d or frequency f and G3 could be obtained. Based on the above, the optimized structure or art parameters of the detector can be selected and some effective methods for improving its properties will be considered.
1992, 41 (10): 1686-1693. doi: 10.7498/aps.41.1686
Considering layer-structural characteristico of high-Tc superconductors, the effective Hamiltonian is derived within linear spin wave approximation for aniso-tropic three-dimensional Hubbard model in the large U limit. The Sublattice magnetization, internal energy, Specific heat, parallel and perpindicular susceptibilies of the system are Calculated by using the equation of motion for matrix Green's function. It is shown that the ratio (δ=J⊥/J) of antiferromagnetic interplanar Coupling to planar coupling has an important effect upon these quantities. In the Low temperature regime T?2J(2+δ)/kB, a characteristic temperature T0=2J(2δ(2+δ))1/2/kB is given, the asympototic expressions of these quantities are respectively obtained for T?T0 and T?T0.
1992, 41 (10): 1694-1699. doi: 10.7498/aps.41.1694
Changes of permeability have been measured for as-received amorphous (Fe1-xNix)76Si8B16 alloys after aging for different times at relative low temperatures (65-150℃). The results indicate that the permeability is almost unchanged after aging below 65℃ but it varies obviously above 100℃. The changes of permeability are dependent on the alloy compositions and can be interpreted in terms of the changes of stress, magnetostriction and induced magnetic anisotropy during aging.
1992, 41 (10): 1700-1705. doi: 10.7498/aps.41.1700
Using in situ electron spin resonance(ESR) technique, we have studied the type, the density, the temperature dependence and the thermal dynamic behavior of defects in rf-reactively sputtered a-Ge1-xCx: H films. In the decomposition process of the ESR spectra, we found that the spectra have an asymmetrical component. Quantitative analysis of the component and the explanation of its origin are given.
1992, 41 (10): 1706-1714. doi: 10.7498/aps.41.1706
When a He-Ne laser beam (632.8 nm) with the power of milliwatts or submilliwatts penetrates through a Mn doped KNSBN crystal, a phenomenon of strong backward scattering is observed. At the same time, an optical diode effect which is associated with the backward scatering is also observed. In a certain range, the response time constant T of the optical diode effect is inversely propotional to the incident intensity on the surface of the crystal. The τ is decreased by one order of magnititude when a K9 glass plate which serves as a feedback mirror is introduced. A time constant of 1.5s and a ratio of the forward transmissivty to the backward one, which is greater than 15.3, have been obtained. A theoretical explanation is given on the basis of the experimental results
1992, 41 (10): 1715-1721. doi: 10.7498/aps.41.1715
This paper presents the effects of the interaction potentials(Moliére pntpntial and Universal potential) on computer simulation results of sputtering via Monte Carle simelation based on the binary collision approximation. By means of Wilcoxon two-Sample paired sign rank test, the statistically significant difference for the above results is ob tainad.
1992, 41 (10): 1722-1727. doi: 10.7498/aps.41.1722
The angular distributions of atoms sputtered from Ni-50Wt%Ti, Fe-30Wt%W and Ag-50Wt%Cu alloys by 27keV Ar+ ions bombardment nave been masured. It has been found that Ti, Fe and Ag atoms were sputtered preferentially at small angles. The sputtered surfaces have been analyzed by SEM combined with EPMA. It has been showed that all the surface topographies of three samples consisted of two different parts i.e. convex and concave regions, corr responding dif ferent components being richer at different region. A model has been suggested to explan this phenomenon.
INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
1992, 41 (10): 1728-1736. doi: 10.7498/aps.41.1728
Temperature effects on interaction between P and GaAs (100) surface have been studied by in-situ X-ray photoemssion, uhra violet photcemission, high resolution electron energy loss specrroscopy and low energy electron diffraction techniques. The results show that annealing will make most of the amorphous P, which are deposited on GaAs(lOO) surface at room temperature, desorb with some randomly distributed P-clusters left on the surface. In these clusters, some of the P atoms are bonded to the Ga atoms of the substrate, others exist in the form of element. Higher temperature annealing will make all the left P atoms interact with the substrate and form GaAsP thin layer. Film of GaAsP solid solution will be obtained when depositing P on high temperature GaAs substrate. This film is suggested to be a promissing passi-vating film for GaAs surface.