Vol. 42, No. 7 (1993)
ATOMIC AND MOLECULAR PHYSICS
1993, 42 (7): 1025-1030. doi: 10.7498/aps.42.1025
The oscillator strengths and lifetimes for some states of Mg are calculated by using model-potential wavefunctions. After comparing the results with previous theoretical and experimental data, it is concluded that for many states with weaker configuration mixing, these-quantities can be well calculated by such single configuration wavefunctions.
A fluorescence detection system is described in this paper. By means of thermal atomization and laser resonance excitation technique, the system can measure the lifetimes of atomic fluorescence of refractory metals and therefore the lifetimes of the atomic energy levels. The measured lifetime of Rul energy level [4d65s(6D)5p]7P40 is 70.4(±5%)ns.
1993, 42 (7): 1034-1041. doi: 10.7498/aps.42.1034
In a laser field, for the electron scattered by Coulomb potential, when the wave function is expanded by Floquet partial wave, the Schr?dinger equation separates into the radial form by separation of variables. The system of equations for the radial wave function is infinitely coupling linear second order differential equations. When weak laser field is aonsidered as a pertubation, the equations can be reduced into second order ordinary differential equations and they are integrable. The radial wave function S-matrix and the cross section are obtained. Finally, the resonance lines appear for different cases of polarizations no matter whether the dipole approximation is used. The resonance energies, the intensities of resonance lines are also obtained.
1993, 42 (7): 1074-1078. doi: 10.7498/aps.42.1074
First the resonant eigenfunctions are obtained by using the Floquet theory. Then the dissociation probabilities are gained by solving the coupled matrix of bound state with continunm state. From the above studies, we have got the decay widths of bound states, the resonant energy positions and dissociation probabilities of bound states. Using the quasi-classical theo-ry and above formulas, we have eonducted some calaulation about decay widths of nonrotat-ing, diatomic molecules in the ground electronic state absorbing one photon or two photons.
THE EFFECT OF NEGATIVE-ENERGY MODE ON NONLINEAR INSTABILITY IN DRIVEN DRIFT WAVES (I)——TRANSITION TO POSITIVE-ENERGY MODE AND THE BISTABILITY
1993, 42 (7): 1035-1041. doi: 10.7498/aps.42.1035
In the nonlinear drift-waves driven by a sinucoidal wave, every mode has a resonance regime correspondingly in the parameter space of the driving frequency and strength. Feeding of the applied wave energy causes the transition of a resonant negative-energy mode to positive-energy one. This transition is relevant to the development of bistability of the system in the corresponding regime.
THE EFFECT OF NEGATIVE ENERGY MODE ON NONLINEAR INSTABILITY IN DRIVEN DRIFT WAVES (Ⅱ)——EXCHANGE WITH POSITIVE-ENERGY MODE,‘AVOIDED-CROSSING' AND THE HOPF BIFURCATION
1993, 42 (7): 1042-1049. doi: 10.7498/aps.42.1042
In the nonlinear drift-waves driven by a sinucoidal wave, with variations of the driving frequency and strength, crossing and ‘avoided crossing' may appear between the nonlinear complex eigenvalues of a negative-energy mode and a positive-energy mode. While the ‘avoided crossing' occurs, the positions of these two modes are somehow exchanged. Such nonlinear resonance is related to the Hopf bifurcation in weak dissipations.
1993, 42 (7): 1050-1056. doi: 10.7498/aps.42.1050
Transforming the Coulomb problem to harmonic osillator, we construct nonspreading coherent states for the 2D and 3D hydrogen atom and show that the expectation values of the observables in Q. M. follow the classical Kepler orbits in physical space. The use of a fictitious time variable in the associated auxiliary osillator problem plays a crucial role.
1993, 42 (7): 1057-1062. doi: 10.7498/aps.42.1057
By making use of the Fock States of the q-deformed quantum oscillator which possesses the symmetry of quantum group, we construct the Glauber coherent state of the q-deformed quantum oscillator (the q-Glauber coherent state ㄧα>q). We discuss the of completeness properties, particle number distribution, oscillator strength distribution and the minimal uncertainty principle of the q-Glauber coherent states, and point out that the coherent degree of the q-Glauber coherent state can be described by the parameter q.
A BOHM QUANTUM-POTENTIAL DESCRIPTION FOR THE WAVE EQUATION OF SCALAR PARTICLE IN GRAVITATIONAL FIELD
1993, 42 (7): 1063-1066. doi: 10.7498/aps.42.1063
Introducing Bohm quantum-potential, from Klein-Gordon equation for scalar particle in gravitational field, an equation of trajectory-motion equation can be derived, it is similar to the classical one and it can be reduced to a geodesic equation in a redefined metric space.
CLASSICAL AREA OF PHENOMENOLOGY
1993, 42 (7): 1042-1048. doi: 10.7498/aps.42.1042
In this paper, we investigate the time evolution of the atomic operators of a two-level atom interacting with the field via a two-photon process within and without the rotating-wave approximation (RWA) by means of non-relativestic QED. We also verified that the virtual photon field is the cause for quantum chaos embodied by the periodic decay and revival effect of the atom using the numerical and analytic methods, and discussed the reason of neglecting the in-fluence of the virtual photon field on the revival time.
1993, 42 (7): 1049-1057. doi: 10.7498/aps.42.1049
In this paper, we have studied the nonlinear interaction of two cascade three-level atoms with single mode field. The results show that the cooperative emission of two atoms can translate into synchronous when the strength of exciting field reaches a certain threshold, That is self-organization may occur in many-atom system to form a "large atom system" at the thre-shold, producing synchronous ordered emission Meanwhile, the second-order correlation degree of two-atom system is larger than that of single atom system due to the synchronous emission effect, i.e. bunching is strong but antibunching is weak. Moreover, the deeper squeezing of two-atom system is obtained since many-photon processes become stronger, and the stren-gth of exciting field is reguired to be also stronger.
A NEW METHOD FOR CONSTRUCTING ORTHONORMAL EIGENVECTORS OF HIGH ORDER POWER OF PHOTON ANNIHILATION OPERATOR
1993, 42 (7): 1058-1064. doi: 10.7498/aps.42.1058
In this paper, orthonormal eigenvectors of high order power of photon annihila.tion operator are constructed with N basic vectors of coherent states |aei(2π)/N n〉(n = 0,1,2, …,N-1), and squeezing and antibunching in these states are studied. The results show that squeezing appears only when N = 2 and 4 but antibunching exists for every N.
In solid laser resonator the dioptric srrengh of the thermal focusing lens, 1/f, as a dynamic factor of the resonator, has great influence on the operation characters of the resonator. In this paper, using the transformatin-circie diagrammatic approach, a dynamical analysis on the stability, character of output power ami mode properly of the solid laser resonator is represented in detail. Their relations on the dynamic factor are also derived.
1993, 42 (7): 1074-1079. doi: 10.7498/aps.42.1074
By means of a new formalism of the Kronig-Penney model developed recently, the third order nonlinear optical effect of intersubband transitions in superlattices is studied. It is shown that there is a general relation between optical saturation intensity and tunnel bandwidth. The physical mechanism of this relation is analyzed.
1993, 42 (7): 1079-1085. doi: 10.7498/aps.42.1079
Two-mode squeezed states of light field are experimentally generated by nondegenerate parametric down conversion in an optical cavity. Noise reductions of about 30% relative to the vacuum noise level are obtained in the quiet quadrature of the electromagnetic field.
THE EFFECT OF PHYSICAL PARAMETERS ON THE TEMPERATURE CHARACTERISTICS OF TWO-BEAM COUPLING IN PHOTOREFRACTIVE CRYSTAL
1993, 42 (7): 1086-1091. doi: 10.7498/aps.42.1086
The temperature characteristics of two-beam coupling in photorefractive crystal was discussed by using the one-carrier and one-level band-conduction model. The effect of physical parameters on the temperature characteristics was analyzed generally. In this paper, the concept of thermosenseless range has been put forward. If a crystal operates in this range, the optimum results of high efficiency, small thermonoise and small thermodrift of operation point can be obtained. The relationship between physical parameter and the location and extent of the range has been given, the method to amend experiment has been suggested.
1993, 42 (7): 1067-1073. doi: 10.7498/aps.42.1067
Under the assumption on the temperature independence of the parameters of the Skyrme interactions, the formula of deuteron-nucleus self-consistent microscopic optical potentials are derived with the utilization of the mass operator method of Green function and the semi-classical variation approach. The temperature dependence of d+40Ca and d+90Zr optical potentials at different energies is discussed.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
1993, 42 (7): 1080-1085. doi: 10.7498/aps.42.1080
The properties of vibrational states lor one-dimensional quasi-lattice, specially, properties of critical states are studied. Some methods describing different vibrational states are given.
1993, 42 (7): 1086-1094. doi: 10.7498/aps.42.1086
This paper is devoted to the study of phonon and melting property of two-demensional Per.rose latrice with five-fold rotational symmetric axis. We intrtoduce a similarity transformation which transforms the dynamical matrix into a block-diagonal matrix, which helps to determine analytically the degeneracies of the modes of the phonon spectra and reduce the numerical calculation. It is found that two thirds of the modes are doubly degenerate and the remains are nondegenerate. By using the atomic mean-square displacement criterion, we study the melting property of the two-demensional Penrose lattice. We find that boundary atoms. alawys have lower melting temperature thanthat of bulk, and when the interaction among atoms is larger, the system will have a higher melting temperature.
MULTIPHONON TRANSITION AND TEMPERATURE DEPEN-DENCE OF PHOTOLUMINESCENCE SPECTRA OF DYE J-AGGREGATE LANGMIUR-BLODGETT FILMS
1993, 42 (7): 1095-1100. doi: 10.7498/aps.42.1095
In temperature range of 20K to 300K, we measuded photoluminescence spectra of heterogeneous J-aggregate Langmiur-Blodgett (LB) films made of three kinds of cyanine dye. With temperature reduced, while the intensity of J-peak, the zero phonon line increased, anomalous enhancement of the phonon sideband was observed. Analysis shows that J-aggregatc LB films are of characteristics like that of low dimensional crystal, they have strong phonon coupling, and nonradiative transition plays important role.
STUDY ON THE STRUCTURE、THE ELECTRICAL PROPER-TIES AND THE CONDUCTION MECHANISM OF THE POLYCRYSTAL MULTIPHASE MATERIAL Li2Mo2-xWxO6
1993, 42 (7): 1101-1109. doi: 10.7498/aps.42.1101
The poly crystal multiphase creamics material Li2Mo2-xWxO6 with high conductivity is prepared in reducing atomsphere. By X-ray diffraction, EDX graph, 1R and ESR spectra, it is determined that the sample material is composed of two phases, i.e., Li2Mo1-xWxO4 and MoO2. The addition of tungsten mainly replaces molybdenum in the Li2MoO4 lattice. The electrical properties are studied by a.c. admi tance bridge method and a.c. complex impedance spectroscopy. The conductivity of the sample (x = 0.3) is σ27℃ =1.42×10-2(Ωcm)-1, σ300℃=2.86×10-2(Ωcm)-1. The conductivity increases and the ionic conduction activation energy decreases with increasing tungsten content. The microstructure model and the ionic conduction mechanism are given in this paper.
STABLE SOLUTIONS OF THE LEAST SQUARE SIMULTANEOUS EQUATIONS IN QUANTITATIVE X-RAY PHASE ANALYSIS WITHOUT STANDARDS
1993, 42 (7): 1106-1111. doi: 10.7498/aps.42.1106
The X-ray phase analysis without standards is an important quantitative method. The problem of the abnormal state equation lead to the results of composition with large error. The least square simultaneous equations in some cases of combination also have the problem of the abnormal state equation. The least square simultaneous equations method in the quantitative X-ray phase analysis without standards has been proposed, from which the stable solutions can be found. The calculating methods of the stable solutions in different sample number and combination conditions are indicated.
1993, 42 (7): 1110-1115. doi: 10.7498/aps.42.1110
The experimental method for studying interface atomic structure between amorphous layer and crystal by MeV ion scattering and channeling is described. This method is applied . to study the Al2O3/Al(100) interface. Thin Al oxide film are formed on clean Al(l00) surface in pure oxygen ambience at 400℃. The experimental results show that the composition of the oxide film is precisely Al2O3, and the interface between Al oxide film and Al(l00) bulk is very sharp, the reconstructive layer under the Al2O3 film is no more than one monolayer. Monte carlo simulations indicate the distance between displaced Al atoms on the reconstuctive layer and Al〈l00〉axis is 0.18 A. At room temperature, the oxygen adsorption layer of Al〈l00〉 is primarily stoichiometric A1O at low surface coverages.
1993, 42 (7): 1112-1116. doi: 10.7498/aps.42.1112
The pressure respones of Configuration entropy and information dimension of atomic energy distribution in amorphous iron is aralysed We calculate the particle number distribution of atomic energy, and take the information entropy of it as the configuration entropy of the amorphous structure. The calculated results suggest that the atomic energy distribution curve and the configuration entropy are relate to the energy interual in statistics, e. g., there is a fractal scaling ruler between configuration entropy and the interval. The configuration entropy is determined by the average value of it in no scaling distribution range of atomic energy between lower bound and upper bound. The results of simulation indicate that information dimension is another efficient parameter to describe the degree of disorder in amorphous system, and the effects of pressure on fractal dimension and the degree of structural disorder in amouphous structure show complicated behavior.
1993, 42 (7): 1116-1120. doi: 10.7498/aps.42.1116
Using ASED-MO method and cluster models, the chemisorption energy of Li on Si(l00) 2×1 surface and the interaction between two adsorbed Li atoms are calculated. A new model which can be used to explain the transition from Si(100)-Li(2×1) to Li(l×l) in the 1 mono-layer range is proposed.
1993, 42 (7): 1117-1120. doi: 10.7498/aps.42.1117
An eighty-seven molecule system is used to simulate the C60 crystal. The binding energy of the system is calculated for various relative orientations of the C60 molecules. It is found that the ground state is not a degenerate state with respect to the orientations between molecules. There is an energy minimum when the relative orientation of nearest neighbor C60 molecules take an angle of 29°, which may refer to the ordered state of simple cubic phase at very low temperatures.
1993, 42 (7): 1121-1126. doi: 10.7498/aps.42.1121
Inelastic neutron scattering spectra of YBa2Cu3O6+δ sample with several different oxygen contents δ have been obtained in the energy range from 10 to 150 meV at a new wide angle (～30°) Be-filter detecter spectrometer, CIAE,Beijing. The experiments show that :(l)For samples with δ=0 and δ=0.2, some strong high frequency modes appear in the energy range from ～60 to ～150 meV,and the intensity of modes does not decrease as the temperature is above Neel point until 466K. For samples with δ=0.78 and 0.97, however, the high frequency modes are not present and the scattering intensity spetra in the energe range from 70 to 150 meV seem to be a featureless background. (2)In the measured energe range from 10 to 150 meV the scattering intensities of sample with δ=0 and 0.2 is about two to three times as that of sample with δ = 0.78 and 0.97. (3) In the energe range below 60 meV, there are many distinct scattering peaks which are almost not shifted with δ, most of peaks are in a-greement with results of Renker and Parshin, and other peaks are observed for the first time. The strong dependence of high frequency modes and scattering intensities on the oxygen content δ would attribute to antiferromagnetics spin wave excitation.
1993, 42 (7): 1121-1128. doi: 10.7498/aps.42.1121
GexSi1-x/Si strained-layer superlattices were grown on Si(lOO) substrates under different temperatures by molecular beam epitaxy. Methods such as reflection high energy electron diffraction, X-ray double crystal diffraction, Rutherford back scattering, transmission electron microscopy and Raman scattering have been applied to study the growth and characteristics of the GexSi1-x/Si superlattices. The result show that the optimum growth temperature are different for superlattices with different composition, the smaller the x the higher the growth temperature, and vice versa. For x = 0.1-0.6, the GexSi1-x/Si superlattices with flat interfaces, good crystal perfection and uniform periodicity can be obtained with growth temperature in the range of 400-600℃.
1993, 42 (7): 1129-1133. doi: 10.7498/aps.42.1129
We calculate the lattice heat capacity of layered material based on a simple model with cubic structure and Born potential. It is shown that interface states affect the lattice capacity obviously when the thickness of layer is relatively small (less than several tens of single la-years). With the increasing of thickness of the layer, the lattice capacity decreses and is nearly independent of interface states and the thickness of the layer. We also give a comparison of the lattice capacity of aperiodic superlattice with that of periodic superlattice.
STUDY ON SOLID STATE REACTION INTERDIFFUSION OF Fe-Ti MULTILAYER MODULATED FILMS WITH DYNAMIC IN SITU X-RAY DIFFRACTION
1993, 42 (7): 1134-1140. doi: 10.7498/aps.42.1134
Solid state reaction interdiffusion of Fe-Ti multilayer modulated films was investigated by means of dynamic in situ X-ray diffraction. With this method, the measurement of the X-ray modulation peak intensity was relatively accurate and the shift in X-ray modulation peak position was also observed. The interdiffusion coefficients of Fe-Ti modulated films were calculated at different temperatures. Plots of the interdiffusion coefficients versus time at different temperatures were given. According to the variation rate of D vs. τ, the activation enrrgy Qy relative to viscosity relaxation was calculated to be 8.3±0.2 kcal/mol.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
1993, 42 (7): 1092-1097. doi: 10.7498/aps.42.1092
The influence of resonant helical field (RHF) on tearing mode has been calculated by solving resistive MHD equations, and different widths of saturated island have been obtained while there are different phase differences between plasma perturbation and RHF. It seems that RHF can either increase the width of saturated island, or decrease it.
1993, 42 (7): 1098-1105. doi: 10.7498/aps.42.1098
A theoretical model for the free expansion of a plasma with three and multiple electron temperatures is developed. The three and multiple peak structures exhibited in ion velocity distributions, which have often been observed experimentally, have been reproduced by the self similar solutions successfully. It is shown that the number of the peaks for ion spectra are closely connected with mumber of electron components including in plasma. The depth of the dip between two adjacent peaks is particularly sensitive to the adjacent electron temperature ratio, the position of the dip depends on corresponding electron number density ratio, they are also affected by coupling of the other electron components. The regions in the parameter space where the self similar solutions are available are discussed.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
INFLUENCE OF ELECTRONIC STRUCTURE CHARACTERISTICS OF Fe2O3 NANOMETER PARTICLES ON THEIR OPTICAL PROPERTIES
1993, 42 (7): 1127-1133. doi: 10.7498/aps.42.1127
In this work, we carried out some experimental characterizations on the electronic structure of Fe2O3 nanometer particles, discussed the relationship between the electronic state variance under the quantum confinement, dielectric confinement and interfacial chemical bonding conditions and their optical properties, The experimental results are in good agreement with the recent theoretical considerations qualitatively.
1993, 42 (7): 1134-1139. doi: 10.7498/aps.42.1134
The applieation of the ab-initio LMTO-ASA method to B1 structure crystal is studied in this paper. The important function of the empty atomsphere in the calculation of static properties such as equilibrium lattic constant, bulk modulus and cohesiv energy, and the band structure on Bl MgO crystal are emphatically investigated. A simple LMTO method which is as accurate as the ab-initio pseudopotential method has been adopted. The calculated results of the lattic constant a0 ,bulk moduius B0 and cohesive energy Ec of Bl MgO are 4.21? , 1.58 Mbar and 5. 73eV/atom, respectively, which are very close to experimantal data and those obtained by more complicated ab-initio band calculating methods. The band structure calculated by our method is in good agreement with that by ab-initio pseudopotential method. The results indieate that LMTO-ASA method in which empty atom-spheres is added and L?wdin principle is introduced to raise calculation efficiency is suitable to the study of band structure and static property of Bl structure crystal.
1993, 42 (7): 1140-1148. doi: 10.7498/aps.42.1140
The electron correlation functions in spin-nondegenerate systems are studied in this paper. By using Hartree-Fock approximation, we present the spin-dependent electron correlation functions for neutral soliton, where there is only one up-spin electron on the mid-gap state. We obtain the pictures of spin-dependent correlation functions and discuss their properties.
1993, 42 (7): 1141-1148. doi: 10.7498/aps.42.1141
Under Bose and non-Bose approximations, the squeezing, antibunching and sub-Poisso-nian statistics of one-exciton and two-exciton in the Dicke and Fock superposition states are discussed. The recombination radiation of excitons in these superposition states can also have these non-classical effects. The results obtained in various situations are compared and explained.
1993, 42 (7): 1149-1156. doi: 10.7498/aps.42.1149
The collective excitations of three dimensional tight-binding electron gas system have been studied in the case of three different kinds of structures (s.c.,f .c.c.,b.c.c.). By random phase approximation, we obtain the matrix formulation of the theory.
1993, 42 (7): 1149-1152. doi: 10.7498/aps.42.1149
The work function of Ir(100) surface coated with Cs overlayer is investigated by using jellium sphere/slab model containing three layers of Ir slab. A work function-coverage curve much reasonably closer to the experimental one is lbtained. The theoretical value of work function of clean surface is reduced to 5. 84 eV from the former result of 6.6 eV, which is in good agreement with experiment (5.5 eV). At the minimum, work function rises to 1.02 eV from former one (about 0.2 eV), which is much closer to the experimental result (about 1.3 eV). The relationship between the appearance of work function-coverage curve and the transfer of valence electrons in jellium sphere-vacuum region is analyzed.
VALENCE BAND OFFSET IN PSEUDOMORPHIC Si/Ge0.25Si0.75/Si SINGLE QUANTUM WELL MEASURED BY DEEP LEVEL TRANSIENT SPECTROSCOPY
1993, 42 (7): 1153-1159. doi: 10.7498/aps.42.1153
The band offset between strained GexSi1-x and unstrained Si is mainly due to the valence band offset ΔEv. The thermal emission energy from a quantum well is related to the appropriate band offset. The single quantum well (p type Si/Ge0.25Si0.75/Si) samples were grown by molecular beam epitaxy (MBE), the width of quantum well is 15nm. Deep leve transient spectroscopy (DLTS) measurement have been used to study the valence band offset. After considering the band bending due to the electric field and the first subband energy, the valence band offset ΔEv of the single quantum well was estimated as about 0.19eV, it is in reasonable agreement with theoretical results. The same and difference of emission and capture processess between quantum well and deep level defects were discussed.
1993, 42 (7): 1157-1161. doi: 10.7498/aps.42.1157
Using the multi-channel generalization of Landauer formula, we investigate the adiaba-tic transport and the Ohmic transport of two unequal narrow constrictions in series with a closed cavity in between. It is shown that the adiabatic transmission leads to the nonadditivity of constriction's resistances, and the completely incoherent transport obeys the Ohmic addition rule.
1993, 42 (7): 1160-1166. doi: 10.7498/aps.42.1160
Ag-sheathed Bi1.8Pb0.4Sr2Ca2.2Cu3Oy superconducting tapes were prepared. Microstruc-ture examination shows that it were made of highly textured Bi2223 single phase. Measurements of transport properties in liquid nitrogen and field lower than 1T reveal that Jc(T,B,θ, φ) and R(T,B,θ,φ) of this material are θ dependent and φ independent, where θ is the angle between magnetic field and ab plane and φ is the angle between magnetic field and transport current. Activation energy of flux lines was gained. The Arrhenius relation of R(T,B) was observed and activation energy of flux motion was determined. The transport characteristics and the activation energy are explained as the thermally activated flux line diffusive motion over intrinsic flux pinning barrier by means of nucleation of two-dimensional pancake vortex pairs.
1993, 42 (7): 1162-1173. doi: 10.7498/aps.42.1162
The ground states of phonons in a dissipative quantum tunneling system and their influences on the localiza ion-delocalization transtion are investigated by a variational approach. We find that: 1. There are two kind of influences, displacement and deformation, on phonon states due to coupling with a tunneling particle, and displaced -squeezed states are proposed to describe both these influences. 2. The localization-delocahzation transition depends on the choice of phonon ground state. The transition will occur at strong coupling as the energy of the ground state decreases.
1993, 42 (7): 1167-1171. doi: 10.7498/aps.42.1167
Microwave joining developed rapidly in recent years, because of its advantages such as 1)low energy consnmption; 2)rapid heating rate; 3)high quality joint. Microwave joining of the Bi-based 2223 superconductor was studied with the results showing, after joining at 900-1000℃ for 10 minutes and post treatment at 855℃ for 60 hours, Tc restored to 107 K, the same as that of the original sample. Electron probe technique was used to study the microstructure features before and after joining.
1993, 42 (7): 1172-1178. doi: 10.7498/aps.42.1172
The condensed phases of poly-Cn group are studied by means of the method of quantum field theory in statistical physics. It follows that the transition temperature for poly-Cn group obeys a power law because of the divergence of the density of states at the Fermi level. This class of materials has the possibility of exhibiting high temperature superconductivity.
1993, 42 (7): 1174-1178. doi: 10.7498/aps.42.1174
Two high Tc superconductor YBa2Cu3O7-δ thin films, the zero resistance temperature of which were 82K and 71K respectively, were selected for measurement about resistance broadening. The difference in thermal activation energy of the two samples was analyzed with Arrhenius law auggested by Palstra We found that the activation energy decreased depending upon increasing magnetic field. The irreversibi-lity line was B*-(1-T*/Tc)3/2 deduced from our data.
1993, 42 (7): 1179-1185. doi: 10.7498/aps.42.1179
Based on the fact of the existance of a small amount itinerant electrons, a new theoretical model giving rise to magneto-crystalline anisotropy in compound Nd2Fe14B is presented in this paper. It is proposed that a combined effect on Nd-ion coming from both the crystal field of ligands and the electric field of itinerant electrons results in the anisotropy in the compound. An approach of calculating the interaction between itinerant electrons and central Nd-ion is given. The magneto-crystalline anisotropy of Nd-ion and its temperature dependences are calculated based on the model. The results are in good agreement with the experiments, and also give explanation to the spin reorientation phenomenon in the compound.
1993, 42 (7): 1179-1187. doi: 10.7498/aps.42.1179
In this paper, we propose a generalized mixed spin model on the union jack lattice. The mean field. free-fermion approximations and equiscale transformation in the same universality class method are applied to this model. The critical temperature curves obtained by different methods agree with each other quite well. We also compare the three different methods. In some special cases, the same critical points as in exactly solved models are obtained.
1993, 42 (7): 1186-1192. doi: 10.7498/aps.42.1186
We have stulied the structure and intrinsic magnetic properties of R2Fe17C compounds (R = Y, Sm, Gd, Tb, Dy and Er), and compared them with the corresponding R2Fe17 compounds. The Curie temperatures of R2Fe17C are about 200K greater than those of R2Fe17. We discussed the variation of the structure and magnetism of the compounds due to introducing C atoms. Furthermore,Sm2(Fe1-xCox)17 C compounds have also been studied.
AN INVESTIGATION ON SURFACE STATUS, STRUCTURE RELAXATION AND CRYSTALLIZATION PROCESS OF Fe35Ni15B26 NANOMETER METGLAS
1993, 42 (7): 1188-1193. doi: 10.7498/aps.42.1188
The surface status, structure relaxation and crystallization process of Fe35Ni15B26 nanometer metglas produced by chemical reduction method were investigated by using X-ray photoelectron spectroscopy and M?ssbauer spectroscopy. The experimental results indicated that it is rich in nickel and lack in iron on the oxidized particle surface compared with the bulk composition of the particles. The change of hyperfinc field distributions during structure relaxation is correlated with the variance of short range order. The crystallization product is different from that of traditional amorphous ribbon with the similar composition because of the heterogeneous distribution of elements in particles.
1993, 42 (7): 1193-1200. doi: 10.7498/aps.42.1193
The Faraday rotation caused by electronic transitions between the 4f and 5d states of Ce3+ ions in paramagnetic CeF3 crystals is calculated. The crystal field is an important perturbation on the energy levels. An external magnetic field, together with an additive magnetic field introduced phenomenologically in our paper, would spilt every 4f state into two sublevels. The dipole transitions between these sublevels, and 5d states induce the Faradap effect.The Verdet constant at 0.6328 μm in the temperature range of 60-300 K is obtained. It is shown that our calculation is in good agreement with experiment.
1993, 42 (7): 1194-1198. doi: 10.7498/aps.42.1194
The investigation of ARUPS of nitric oxide adsorbed on Cu(110) is reported here. The results show that it is a complex dissociative process that occurs at 150 K. Varied with the exposure of NO, the different molecules which are dissociated from NO, are adsorbed on Cu (110). With 5L NO the dominant adsorbates are atomic oxygen and N2O molecules. The adsorption LEED pattern is still (1×1). The present problem has been studied by ARUPS, LEED and AES.