Transmission and reflection of soliton in an inhomogeneous plasma are investigated, the transmission and reflection waves both can be described by the KdV equation in the lowest order. The numbers and magnitude of both transmitted and reflected solitons from an incident soliton are given analytically.
Transmission and reflection of soliton in an inhomogeneous plasma are investigated, the transmission and reflection waves both can be described by the KdV equation in the lowest order. The numbers and magnitude of both transmitted and reflected solitons from an incident soliton are given analytically.
New concepts are proposed on the pure states and quantum systems of Berry type, of which the properties and signifieance are discussed. In addition, we point out that an adiabatic system can be approximately regarded as a quantum system of complete Berry type.
New concepts are proposed on the pure states and quantum systems of Berry type, of which the properties and signifieance are discussed. In addition, we point out that an adiabatic system can be approximately regarded as a quantum system of complete Berry type.
Decoupled squeezed states for the Landau System (planar charged particle moving in a uniform magnetic field) are builded. It is convenient to use these states to describe the circular motion of the charged particle. The results obtained do not depend on gauges.
Decoupled squeezed states for the Landau System (planar charged particle moving in a uniform magnetic field) are builded. It is convenient to use these states to describe the circular motion of the charged particle. The results obtained do not depend on gauges.
In this paper the explicit form of composite transformation of n successive Lorentz transformation was obtained, from which the transformation from accelerating system to inertial one was deduced, and the application range of Mller transformation was extended.
In this paper the explicit form of composite transformation of n successive Lorentz transformation was obtained, from which the transformation from accelerating system to inertial one was deduced, and the application range of Mller transformation was extended.
We find a closed cosmological solution for small scale factor in the semi-classical Brans-Dicke theory. The model has an initial space-like curvature singularity.
We find a closed cosmological solution for small scale factor in the semi-classical Brans-Dicke theory. The model has an initial space-like curvature singularity.
A new method of controlling chaos of a laser diode by all external optical feedback was proposed according to the principle of Pyragas' method; the conditions in which the method can be used were given from theoritical analysis based on the coherence theory, and the results of the computer simulation proved that this method was efficient.
A new method of controlling chaos of a laser diode by all external optical feedback was proposed according to the principle of Pyragas' method; the conditions in which the method can be used were given from theoritical analysis based on the coherence theory, and the results of the computer simulation proved that this method was efficient.
The effects of free electrons in a plasma on a complex atom are discussed, here we are interested in the target ionAu50+ in inertia confined fusion(ICF). The results are compared with those in the case of hydrogenic ions. Accurate numerical solutions have been obtained for Schrdinger's equation through Debye screened Hartree-Fock-Slater self-consistent potential. Solutions have been computed for 28 eigenstates, 1s through n=7, l=6,yielding the energy eigenvalues for a wide range of Debye screening length Λ. As in the case of hydrogenic ions, under screening, all energy levels are shifted away from their unscreened values toward the continuum, that is, the ionization limits are shifted downward. Conclusions have been made that when Λ＞5a0， that is, in the weak screening case, Debye screening has little effect on oscillator strength, average obital radius, transition matrix elements, etc., of Au50+. For each (n,l) eigenstate, there is a finite value of screening length Λ0(n,l), for which the energy becomes zero. When Λ is sufficiently small, level crossing appears at high n satets. Optical oscillator strength for Au50+ has also been calculated, the results are compared with those under unscreened potential.
The effects of free electrons in a plasma on a complex atom are discussed, here we are interested in the target ionAu50+ in inertia confined fusion(ICF). The results are compared with those in the case of hydrogenic ions. Accurate numerical solutions have been obtained for Schrdinger's equation through Debye screened Hartree-Fock-Slater self-consistent potential. Solutions have been computed for 28 eigenstates, 1s through n=7, l=6,yielding the energy eigenvalues for a wide range of Debye screening length Λ. As in the case of hydrogenic ions, under screening, all energy levels are shifted away from their unscreened values toward the continuum, that is, the ionization limits are shifted downward. Conclusions have been made that when Λ＞5a0， that is, in the weak screening case, Debye screening has little effect on oscillator strength, average obital radius, transition matrix elements, etc., of Au50+. For each (n,l) eigenstate, there is a finite value of screening length Λ0(n,l), for which the energy becomes zero. When Λ is sufficiently small, level crossing appears at high n satets. Optical oscillator strength for Au50+ has also been calculated, the results are compared with those under unscreened potential.
Upconversion fluorescence near 553 and 410nm was detected when the Er3+-doped yttrium vanadate (Er3+∶YVO4) crystal was excited with a 808nm-diode laser and a 658nm-dye laser. Analysis of excitation mechanism shows that excited state absorption dominantly contributes to the upconversion emissions. Measurement of lifetimes for different Er3+ concentration indicates that the lifetime of 553nm emission decreases with increasing Er3+ concentration, but no considerable changes of that of 410nm emission have been observed. With the consideration of the fact that the intensity of 553nm band declines with increasing Er3+ concentration, we argue that in the concentration range measured there is an appreciable concentration quenching in the 553nm emission, and a dominant population channel of its upper state (4S3/2) is the nonradiative relaxation from the upper state (2H9/2) of the 410nm band.
Upconversion fluorescence near 553 and 410nm was detected when the Er3+-doped yttrium vanadate (Er3+∶YVO4) crystal was excited with a 808nm-diode laser and a 658nm-dye laser. Analysis of excitation mechanism shows that excited state absorption dominantly contributes to the upconversion emissions. Measurement of lifetimes for different Er3+ concentration indicates that the lifetime of 553nm emission decreases with increasing Er3+ concentration, but no considerable changes of that of 410nm emission have been observed. With the consideration of the fact that the intensity of 553nm band declines with increasing Er3+ concentration, we argue that in the concentration range measured there is an appreciable concentration quenching in the 553nm emission, and a dominant population channel of its upper state (4S3/2) is the nonradiative relaxation from the upper state (2H9/2) of the 410nm band.
In this paper we derive the Fokker-Planck equation of a closed lasing system by using ordering techniques of operators, reduce it to an equation including merely field variables, and then obtain the Q function of the laser field. Through analyzing the Q function, we discover that,at the operating point, the dynamic behavior of the dipole moment between the lasing levels decisively influences the quantum statistical properties of the laser field. Under certain conditions we obtain a clear picture about the influence. The conclusion can be applied to a variety of laser systems, including those without inversion.
In this paper we derive the Fokker-Planck equation of a closed lasing system by using ordering techniques of operators, reduce it to an equation including merely field variables, and then obtain the Q function of the laser field. Through analyzing the Q function, we discover that,at the operating point, the dynamic behavior of the dipole moment between the lasing levels decisively influences the quantum statistical properties of the laser field. Under certain conditions we obtain a clear picture about the influence. The conclusion can be applied to a variety of laser systems, including those without inversion.
The ［(Ni80Fe20)1.4nm/Moxnm］30 magnetic multilayers(x=0.7,1.6,2.1) have been investigated by selected area electron diffraction and high resolution electron microscopy (HREM).It is revealed that:(a) The structure of the NiFe/Mo multilayer changes with the increase of the thickness of Mo spacer-layer. The NiFe and Mo layers are mainly amorphous as the Mo spacer is 0.7 nm in thickness, and crystallized into polycrystalline fcc NiFe and bcc Mo layers as the Mo spacer is thicker than 1.6nm. (b) For the multilayers with Mo spacer of 1.6nm and 2.1nm in thickness , there are two types of orientation relationship between the fcc NiFe and bcc Mo:(110)Mo∥(111)NiFe，［111］Mo∥［110］NiFeand(110)Mo∥(111)NiFe，［001］Mo∥［110］NiFe.(c) The NiFe /Mo interfaces are sharp in case (b) but the lattice spacing varies near the interface region as the lattice spacing of NiFe expands and that of Mo contracts with respect to their bulk counterparts. The variation of lattice spacing near the interfacial region has been discussed and the absence of giant magneto-resistance has been interpreted by the structural characteristics of the multilayers.
The ［(Ni80Fe20)1.4nm/Moxnm］30 magnetic multilayers(x=0.7,1.6,2.1) have been investigated by selected area electron diffraction and high resolution electron microscopy (HREM).It is revealed that:(a) The structure of the NiFe/Mo multilayer changes with the increase of the thickness of Mo spacer-layer. The NiFe and Mo layers are mainly amorphous as the Mo spacer is 0.7 nm in thickness, and crystallized into polycrystalline fcc NiFe and bcc Mo layers as the Mo spacer is thicker than 1.6nm. (b) For the multilayers with Mo spacer of 1.6nm and 2.1nm in thickness , there are two types of orientation relationship between the fcc NiFe and bcc Mo:(110)Mo∥(111)NiFe，［111］Mo∥［110］NiFeand(110)Mo∥(111)NiFe，［001］Mo∥［110］NiFe.(c) The NiFe /Mo interfaces are sharp in case (b) but the lattice spacing varies near the interface region as the lattice spacing of NiFe expands and that of Mo contracts with respect to their bulk counterparts. The variation of lattice spacing near the interfacial region has been discussed and the absence of giant magneto-resistance has been interpreted by the structural characteristics of the multilayers.
The phase transition of liquid crystal carboxylate is studied by using low-frequency internal friction method, under forced-vibration mode. A relationship between the height of the peak of internal friction and the vibration frequency is derived with a simple viscoelastical Maxwell model; it shows a nonlinear feature. The experimental result agrees with this relationship.
The phase transition of liquid crystal carboxylate is studied by using low-frequency internal friction method, under forced-vibration mode. A relationship between the height of the peak of internal friction and the vibration frequency is derived with a simple viscoelastical Maxwell model; it shows a nonlinear feature. The experimental result agrees with this relationship.
The vacancy formation energy in metal Al have been computed by a first-principles pseudopotential method. The dependence of the calculated vacancy formation energy on the supercell size and k point sampling set have been studied in detail. Our results show that the atomic sites in the supercell should reach about 100 in order to have a convergent theoretical value for the vacancy formation energy in Al. The theoretical value using a supercell of 108 atomic sites is in excellent agreement with experimental data.
The vacancy formation energy in metal Al have been computed by a first-principles pseudopotential method. The dependence of the calculated vacancy formation energy on the supercell size and k point sampling set have been studied in detail. Our results show that the atomic sites in the supercell should reach about 100 in order to have a convergent theoretical value for the vacancy formation energy in Al. The theoretical value using a supercell of 108 atomic sites is in excellent agreement with experimental data.
In this paper the ultraviolet—visible photoabsorption spectrum of the complex thin films of noble metal (Au,Cu) particles embedded in BaO matrix is measured.The absorption spectra of the two kinds of films are quite different.There are surface plasmon mode and band transition absorption in the spectrum of the Au-BaO thin film.However,several peaks appear in the spectrum of the Cu-BaO thin film,because Cu exists as very small particles in the matrix.The absorption spectrum is dependent on the metal content.
In this paper the ultraviolet—visible photoabsorption spectrum of the complex thin films of noble metal (Au,Cu) particles embedded in BaO matrix is measured.The absorption spectra of the two kinds of films are quite different.There are surface plasmon mode and band transition absorption in the spectrum of the Au-BaO thin film.However,several peaks appear in the spectrum of the Cu-BaO thin film,because Cu exists as very small particles in the matrix.The absorption spectrum is dependent on the metal content.
Shubnikov-de Haas (SdH) oscillation and quantum Hall effect measurements on pseudomorphic InGaAs/InAlAs modulation doped heterostructure,grown by gas source molecular beam epitaxy,have been carried out to investigate the magetotransport properties of the two-dimensional electron gas in the strained InGaAs quantum well.The SdH measurements at 0.3K demonstrated the existence of a quasi-two-dimensional electron gas in the pseudomorphic InGaAs/InAlAs heterostructure.The fast Fourier transformation results for the SdH data clearly indicate the occupation of two subbands in InGaAs strained quantum well.Comparison between SdH data on the structure with undoped InGaAs cap layer and the structure with heavily Si doped cap layer reveals that different doping in cap layer has large effect on the parallel conductance of the modulation doped structure.
Shubnikov-de Haas (SdH) oscillation and quantum Hall effect measurements on pseudomorphic InGaAs/InAlAs modulation doped heterostructure,grown by gas source molecular beam epitaxy,have been carried out to investigate the magetotransport properties of the two-dimensional electron gas in the strained InGaAs quantum well.The SdH measurements at 0.3K demonstrated the existence of a quasi-two-dimensional electron gas in the pseudomorphic InGaAs/InAlAs heterostructure.The fast Fourier transformation results for the SdH data clearly indicate the occupation of two subbands in InGaAs strained quantum well.Comparison between SdH data on the structure with undoped InGaAs cap layer and the structure with heavily Si doped cap layer reveals that different doping in cap layer has large effect on the parallel conductance of the modulation doped structure.
Two kinds of metal-organic complex thin films Ag-TCNQ and Ag-BDCB have been prepared by the modified thermal evaporation method.transimssion electron microscopy (TEM) and ultraviolet—visible (UV—Vis) spectroscopy were applied to the study of the structures of the metal-organic complex thin films.The TEM and UV—Vis spectroscopic results show that the two kinds of thin films belong to the system of metallic clusters embedded in π-conjugated organic media.
Two kinds of metal-organic complex thin films Ag-TCNQ and Ag-BDCB have been prepared by the modified thermal evaporation method.transimssion electron microscopy (TEM) and ultraviolet—visible (UV—Vis) spectroscopy were applied to the study of the structures of the metal-organic complex thin films.The TEM and UV—Vis spectroscopic results show that the two kinds of thin films belong to the system of metallic clusters embedded in π-conjugated organic media.
We present descriptions of the pairing symmetry in high-temperature superconductors.Analysis of the Josephson tunneling experiments based on the asymptotic s±id state has, to some extend,demonstrated the validity of the model,and the comparison of the theoretical calculations with the dichromatic observations in this kind of material has been in favor of the Γ1+Γ4 representation argument.The possible appearance of the fractional quantum flux vortex related to the specific mixed pairing symmetry has also been discussed.
We present descriptions of the pairing symmetry in high-temperature superconductors.Analysis of the Josephson tunneling experiments based on the asymptotic s±id state has, to some extend,demonstrated the validity of the model,and the comparison of the theoretical calculations with the dichromatic observations in this kind of material has been in favor of the Γ1+Γ4 representation argument.The possible appearance of the fractional quantum flux vortex related to the specific mixed pairing symmetry has also been discussed.
Structural and magnetic properties of Er2(Fe1-xCox)15Ga2 compounds with x=0-1.0 were investigated by means of X-ray diffraction and magnetization measurements.X-ray diffraction patterns demonstrate that all samples are single phase with the hexagonal Th2Ni17-type structure.The lattice parameters a,c and the unit cell volumes V are found to decrease linearly with increasing Co concentration.With increasing Co content the saturation magnetization decreases while,but the Curie temperature increases monotonically.The substitution of Co for Fe has a significant effect on the magnetocrystalline anisotropy,and changes the easy magnetization direction from the basal plane to the c-axis at room temperature for x lying between 0.2 and 0.4.The spin reorientation transitions are observed for x＜0.5.The spin reorientation temperature Tsr increases with increasing Co concentration from 127.8K for x=0 to 558K for x=0.4.
Structural and magnetic properties of Er2(Fe1-xCox)15Ga2 compounds with x=0-1.0 were investigated by means of X-ray diffraction and magnetization measurements.X-ray diffraction patterns demonstrate that all samples are single phase with the hexagonal Th2Ni17-type structure.The lattice parameters a,c and the unit cell volumes V are found to decrease linearly with increasing Co concentration.With increasing Co content the saturation magnetization decreases while,but the Curie temperature increases monotonically.The substitution of Co for Fe has a significant effect on the magnetocrystalline anisotropy,and changes the easy magnetization direction from the basal plane to the c-axis at room temperature for x lying between 0.2 and 0.4.The spin reorientation transitions are observed for x＜0.5.The spin reorientation temperature Tsr increases with increasing Co concentration from 127.8K for x=0 to 558K for x=0.4.
Spontaneous shrinking of the second type of dumbbell domains (IID) subjected to both static bias field (Hb) and in-plane field (Hip) were investigated experimentally.It was found that this phenomenon depends on the amplitude,as well as the direction of Hip.In terms of a series of photographs,it was shown that the spontaneous shrinking of those IIDs perpendicular to Hip occurs earlier,and the spontaneous shrinking of those IIDs parallel to Hip occurs later.In addition,it was confirmed that IIDs lose a part of vertical Bloch lines (VBLs) in their walls in the process of spontaneous shrinking.
Spontaneous shrinking of the second type of dumbbell domains (IID) subjected to both static bias field (Hb) and in-plane field (Hip) were investigated experimentally.It was found that this phenomenon depends on the amplitude,as well as the direction of Hip.In terms of a series of photographs,it was shown that the spontaneous shrinking of those IIDs perpendicular to Hip occurs earlier,and the spontaneous shrinking of those IIDs parallel to Hip occurs later.In addition,it was confirmed that IIDs lose a part of vertical Bloch lines (VBLs) in their walls in the process of spontaneous shrinking.
The electrical bistability of the two kinds of complex thin films Ag-TCNQ and Ag-BDCB was discussed,which were films of metallic clusters embedded in π-conjugated organic media.And infrared spectroscopy was applied to the study of the mechanism.The pump-probe method was used to study the transient response of these two kinds of thin films, the therotical analysis demonstrates that the transient response can be associated with the electrical stability qualitatively.
The electrical bistability of the two kinds of complex thin films Ag-TCNQ and Ag-BDCB was discussed,which were films of metallic clusters embedded in π-conjugated organic media.And infrared spectroscopy was applied to the study of the mechanism.The pump-probe method was used to study the transient response of these two kinds of thin films, the therotical analysis demonstrates that the transient response can be associated with the electrical stability qualitatively.
To study the influence on the optical properties of metal imposed by neighboring medium,we used Dove prisms with different refractive indexes as the substrate in experiment.The noble metal films of Au and Ag were deposited on the bottom of prisms.The dielectric functions for films at the metal-air and metal-substrate interfaces were measured by the spectroscopic ellipsometric method.We found that the dielectric functions of the film measured at the metal-substrate interface do change with the refractive index of the neighboring medium and differ from that measured at the metal-air interface in both the Drude and interband transition regions.The results obtained in a solid-contacting configuration agree with those observed by other authors in a liquid-contact condition,however they cannot be well understood by the known mechanisms.
To study the influence on the optical properties of metal imposed by neighboring medium,we used Dove prisms with different refractive indexes as the substrate in experiment.The noble metal films of Au and Ag were deposited on the bottom of prisms.The dielectric functions for films at the metal-air and metal-substrate interfaces were measured by the spectroscopic ellipsometric method.We found that the dielectric functions of the film measured at the metal-substrate interface do change with the refractive index of the neighboring medium and differ from that measured at the metal-air interface in both the Drude and interband transition regions.The results obtained in a solid-contacting configuration agree with those observed by other authors in a liquid-contact condition,however they cannot be well understood by the known mechanisms.
We have studied the vacancy type defects of the HgCdTe crystals by using positron annihilation time technique.Samples grown by Te solution method accommodate a large amount of Hg vacancies,no matter what kind of conducting type(n type or p type) they are.By suitable annealling process the as-grown p-type samples can be turned into n-type,and the traping of the positrons decreased(the positron annihilation time decreases by 14—17ps).If the samples are annealled at higher temperatrue,the positron annihilation time will increase.This indicates that the Hg vacancies are increased.The bulk time of the positron annihilation in HgCdTe we obtained in this experiment is 272ps.According to the positron annihilation time and the electric parameters of the samples,we obtain the appropriate annealling temperature is 180—220℃.
We have studied the vacancy type defects of the HgCdTe crystals by using positron annihilation time technique.Samples grown by Te solution method accommodate a large amount of Hg vacancies,no matter what kind of conducting type(n type or p type) they are.By suitable annealling process the as-grown p-type samples can be turned into n-type,and the traping of the positrons decreased(the positron annihilation time decreases by 14—17ps).If the samples are annealled at higher temperatrue,the positron annihilation time will increase.This indicates that the Hg vacancies are increased.The bulk time of the positron annihilation in HgCdTe we obtained in this experiment is 272ps.According to the positron annihilation time and the electric parameters of the samples,we obtain the appropriate annealling temperature is 180—220℃.
The characteristics of the construction of one-dimensional Fibonacci-class quasilattices (1D FC(n)) have been described.By means of the electric field theory and the properties of unimodular matrix,we studied extensively the transmissive properties of light through multilayers constructed following 1D FC(n) sequence and found that the transmission coefficient for FC(2m) is switch-like(on-off-on-off-…) and there exist six circulative properties for the one of FC(2m+1) around δ=π(1/2±k), in which the number of transmission coefficient shows interesting properties.
The characteristics of the construction of one-dimensional Fibonacci-class quasilattices (1D FC(n)) have been described.By means of the electric field theory and the properties of unimodular matrix,we studied extensively the transmissive properties of light through multilayers constructed following 1D FC(n) sequence and found that the transmission coefficient for FC(2m) is switch-like(on-off-on-off-…) and there exist six circulative properties for the one of FC(2m+1) around δ=π(1/2±k), in which the number of transmission coefficient shows interesting properties.
Light-emitting hydrogenated nano-crystalline silicon (nc-Si∶H) films have been fabricated using plasma-enhanced chemical-vapor deposition method.It was found that photoluminescence(PL) properties are directly related to grain size and surface strucuture.The quantum size effect and surface states model was proposed to explain PL.Meanwhile,temperature dependence of PL peak energy and integrated intensity are also studied.The former is mainly caused by band-gap shrinkage and the PL intensity decrease with increasing temperature can be interpreted using a temperature independent radiative term and a temperature-dependent thermally activated non-radiative one.
Light-emitting hydrogenated nano-crystalline silicon (nc-Si∶H) films have been fabricated using plasma-enhanced chemical-vapor deposition method.It was found that photoluminescence(PL) properties are directly related to grain size and surface strucuture.The quantum size effect and surface states model was proposed to explain PL.Meanwhile,temperature dependence of PL peak energy and integrated intensity are also studied.The former is mainly caused by band-gap shrinkage and the PL intensity decrease with increasing temperature can be interpreted using a temperature independent radiative term and a temperature-dependent thermally activated non-radiative one.
Cubic boron nitride (c-BN) thin films were deposited on silicon,nickel,stainless steel and Ni-coated silicon substrates by hot filament enhanced plasma chemical vapor deposition (CVD).The films were characterized by infrared spectroscopy(IR), X-ray diffraction, scanning electron microscopy(SEM),and X-ray photoelectron spectra(XPS).It was found that the quality of c-BN thin films varied with deposition conditions and substrates.Under optimum conditions,thin films with high percentage of c-BN and good adhesion were deposited on Ni substrate.When sputtering a Ni interlayer on Si substrate prior to the growth,the c-BN content of the films increased and an excellent adhesion was obtained.
Cubic boron nitride (c-BN) thin films were deposited on silicon,nickel,stainless steel and Ni-coated silicon substrates by hot filament enhanced plasma chemical vapor deposition (CVD).The films were characterized by infrared spectroscopy(IR), X-ray diffraction, scanning electron microscopy(SEM),and X-ray photoelectron spectra(XPS).It was found that the quality of c-BN thin films varied with deposition conditions and substrates.Under optimum conditions,thin films with high percentage of c-BN and good adhesion were deposited on Ni substrate.When sputtering a Ni interlayer on Si substrate prior to the growth,the c-BN content of the films increased and an excellent adhesion was obtained.
SiC buried layers were snythesized by a metal vapor vacuum arc ion source,with C+ ions implanted into crystalline Si substrates.According to X-ray photoelectron spectroscopy,the characteristic electron energy loss spectra of the SiC buried layers were studied.It was found that the characteristic electron energy loss spectra depend on the profiles of the carbon content,and correlate well with the order of the buried layers.
SiC buried layers were snythesized by a metal vapor vacuum arc ion source,with C+ ions implanted into crystalline Si substrates.According to X-ray photoelectron spectroscopy,the characteristic electron energy loss spectra of the SiC buried layers were studied.It was found that the characteristic electron energy loss spectra depend on the profiles of the carbon content,and correlate well with the order of the buried layers.