Vol. 46, No. 5 (1997)
The association and difference between general angular momentum and orbital angular momentum are discussed. Their association lies in the identity of local property (Lie algebra) between group SU (2) and SO (3) (isomorphism), while their difference is their distinctive integral property. The minimal unit ?/2 of the general angular momentum is determined by the local properties of the groups, namely the commutation relation of Lie algebra (or commutor of angular momentum). However, the minimal unit ? of orbital angular momentum depends upon the integral property of group SO (3).
1997, 46 (5): 841-845. doi: 10.7498/aps.46.841
In the continuum limit, the critical phenomenon of the quantum Ashkin-Teller(A-T) chain is discussed by the bosonization method. A new critical region of the A-T chain besides the Ising decoupling point has been found.
1997, 46 (5): 846-851. doi: 10.7498/aps.46.846
The geodesic equations of a test particle are used as the starting point for calculating the effect of perihelion advance, caused by rotating charge. Compared with that of Kerr field, the correction terms enhance the advance effect as the revolutionary direction of particle coincides with that of field source. Moreover, by introducing local Lorentz spacial section, the acceleration of a moving body in this field can be given. It is easy to show that particles cannot arrive at field source from the axis direction or from equatorial plane, but can be held up at r＝k＋(k2＋4m2ａ2)1/2/2m or r=k/m in comoving coordinates (vi=0). In a way, the accretive effect of galatic dust, i.e. the distribution of dust can be calculated then. Finally, the Coriolis-like acceleration of the moving body circling around the source on equatorial plane (only v3≠0) is also discussed.
ATOMIC AND MOLECULAR PHYSICS
MAKING LOCAL MODE VIBRATION LONG LIVED BY THE INTERACTION BETWEEN A STRONG MONO-COLOR LASER FIELD AND MOLECULES
1997, 46 (5): 852-861. doi: 10.7498/aps.46.852
A general semi-classical model of wave packet excitation and evolution in strong single-color laser field has been set up. The simulating calculation demonstrated that a local mode vibration can be selectively excited by a strong resonant laser field, provided that the transition dipole moment from the ground state to the local mode vibrational state is much larger than those of the background (“bath”) states which are coupled with the local mode state.
DEVELOPMENT STUDY OF (e,2e) ELECTRON MOMENTUM SPECTROMETER AND MEASUREMENT OF ELECTRON-MOMENTUM SPECTRUM OF SEVERAL ATOMS AND MOLECULARS
1997, 46 (5): 862-869. doi: 10.7498/aps.46.862
A versatile (e,2e) spectrometer has been successfully developed.The electron beam impacts with the gas beam at right cross. The position sensitive detector with micro-channel plate multipliers and resistive anodes have been developed.An on-line multi-parameter data acquisition technique and off-line data analysis are used.The distributions of separation energies and momentum profiles of Ar,He atoms and H2,CH4 moleculars have measured.
In this paper,the ground state potential surface of Na3 is calculated by employing the discrete variational method.The calculated ground state equilibriun geometry,vibrational frequencies,Jahn-Teller stability energy and Jahn-Teller localization energy are in good agreement with the experimental data.
1997, 46 (5): 878-882. doi: 10.7498/aps.46.878
By using magnetic controlled sputtering of-atoms and evaporating insulator medium, Cu clusters embedded in CdS, a metal-semiconductor film Cu∶CdS has been successfully prepared. TEM is used in studying the microstructure of Cu clusters embedded in the medium CdS. The copper cluster is well embedded in CdS. The size of the triangle-shaped grains, Cu clusters, is from 5nm to 20nm. The Cu cluster and medium CdS are both of polycrystalline structures. And the Cu cluster′s lattice constant expands by about 7%.
CLASSICAL AREA OF PHENOMENOLOGY
1997, 46 (5): 883-891. doi: 10.7498/aps.46.883
In this paper the dependence of peak and bandwidth of resonance fluorescence spectrum for two-and three-atom systems on the Rabi frequency is studied,and the effects of self absorption and stimulated emission on these peaks and bandwidths are also considered.
1997, 46 (5): 892-896. doi: 10.7498/aps.46.892
A new plasma maser scheme,the ion-channel electron cyclotron maser (ICECM) is proposed.By making use of the three-dimensional fluid theory,the dispersion relation of the ICECM with circular orbit electron beam is derived.An ion electrostatic gyro-penitron mode is found,and the growth rate of this new mode is obtained by numerical calculation.
1997, 46 (5): 897-907. doi: 10.7498/aps.46.897
We present a detailed study on the mechanisms of additive hydrogen for high repetition rate copper vapor lasers by solving the kinetics equations of self-consistency in space-time.The mechanisms of the increasing output power by adding small partial pressures of gaseous hydrogen to neon buffer gas are that: (1) the overall copper particles density is increased as the wall temperature increased; (2) the discharge current and the deposited power in the thyratron are decreased while maintaining the same stored input power,and making input power increased.On the other hand,when the additive hydrogen is superfluous (>(1—2)% neon) the plasma electron temperature and electron density decrease obviously owing to the vibrating excitation of hydrogen molecules impacted by the electron,and in this case the laser power decreases.
THEORETICAL AND EXPERIMENTAL STUDIES ON THE CHIRPED PULSE MULTIPASS AMPLIFICATION IN DOUBLE SIDE PUMPED Ti:SAPPHIRE
1997, 46 (5): 908-914. doi: 10.7498/aps.46.908
A novel and more realistic calculation model and method for multipass laser pulse amplification has been put forward based upon the double side pumping scheme. We present here the systematic calculation and analysis on the amplification characteristics of the double side pumped confocal cavity Ti:sapphire amplifier and the chirped pulse multipass amplification through a new amplification configuration. Our experimental results show good agreement with the calculations. With such amplifier,the pass number is noticably reduced and some electro optical elements in regenerative amplifiers have been omitted.
1997, 46 (5): 915-918. doi: 10.7498/aps.46.915
A method of measuring the ratio of thermal emission rate to the photoexcitation constant is presented.The temperature dependence of this ratio for Ce:KNSBN is calculated by using experiment data of two wave mixing.Results show that the calculations and phenomenological theoretic ones coincide with each other very well.
COMPRESSION OF BRIGHT OPTICAL PULSE BY PULSE PAIR IN THE NORMAL DISPERSION REGIME OF SINGLE MODE FIBERS
1997, 46 (5): 919-928. doi: 10.7498/aps.46.919
A novel method that can lead to bright optical pulse compression in the normal-dispersion regime of single mode fiber is proposed.It consists of copropagating a bright pulse with a intense pulse pair in a single mode fiber.Various cases of the bright pulse compression are studied numerically under realistic practical conditions.We found that, as compared with the previous compression method,this method is not only of more practical use but also can achieve better compression of the bright pulse.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
In this paper, an improvement of neutron monochromatization by laminating three slab crystals for a monochromator, was put forward and the corresponding calculating method was given. In order to show the merit of the new method, we have calculated PG, Ge and Si and compared the results. We believed the new method was as effective as the double crystal method and the new one was less complicated.
1997, 46 (5): 938-947. doi: 10.7498/aps.46.938
The occurrence of transitions between two tunneling states of two-level systems(TLS) in glasses is attributed to the coupling to a phonon field. The coupling makes TLS form new “polar coupling states”, we call them as TLS-phonon coupling states. The behaviour of the excitation and de-excitation of TLS coupling states via the interaction with phonon is presented to explain the experimental characteristics of the low-frequency sound absorption in glasses at low temperatures.
1997, 46 (5): 948-952. doi: 10.7498/aps.46.948
The transverse acoustic impedance of an oscillating solid surface in contact with dilute solutions of ３He in 4He is discussed.The calculated values are compared with experiments.A good agreement is achieved.
1997, 46 (5): 953-958. doi: 10.7498/aps.46.953
The investigation of the near-edge X-ray absorption fine structure(NEXAFS) of Na-induced Si(111)3×1 surface structure using the secondary electron partial yield method with synchrotron radiation is reported. Comparing the possible absorption models by the multiple-scattering cluster method, we find that the calculated results by using the Mnch model agree with the experiments.The sodium atom is absorbed on the top site with Na—Si bond length 0.3 nm.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
The infrared photoluminescence spectroscopy was performed for Sb-doped Hg1-xCdxTe(x≈0.38)from 3.9K to 115K. The band to band transition,localized exciton and donor acceptor pair(D0A0)related luminescence peaks were observed. The acceptor level which is related to Sb-doping and about 30 meV above the valence band was observed in photoluminescence experiment in Hg1-xCdxTe(x≈0.38).
1997, 46 (5): 964-968. doi: 10.7498/aps.46.964
By using a newly developed measuring technique,i.e. the quantum capacitance spectroscopy,resonant defect states were observed in the valence band and the conduction band of narrow gap semiconductor InSb and HgCdTe materials. On the basis of a developed experimental model,the properties of the resonant defect states are investigated.
1997, 46 (5): 969-974. doi: 10.7498/aps.46.969
The structures of the strained InGaAs/GaAs ridge quantum wires(QWRs) were proposed and the samples fabricated by MBE growth on patterned substrate. High resolution scanning electron microscope (SEM) studies showed that these ridge structures were formed with (001) top and (113) side faces.The photoluminescence(PL) measurements indicated that the lateral quantum confinement effects of the ridge-QWRs caused the quantum confined energy a 10meV blue-shift, which agreed with the approximate calculations for the strained ridge-QWR structure using Kronig-Penney model. This strainedridge-QWRs consisted of three aspects of lateral confinement effects.Firstly the thickness of ridge quantum wells on the ridge top was larger than that on the side surfaces;Secondly the indium concentrations on the ridge-top region was higher than that on the side region;Thirdly the strain effects led to a larger energy gaps in side (113) plane than that in the (001) ridge top.The above three factors were cooperated to enhance the confinement effects on the lateral motion of carriers in strained ridge QWRs.
1997, 46 (5): 975-980. doi: 10.7498/aps.46.975
The optimal synthesis of T* phase superconductors(Bi0.5Sr1.5)(Y,Ce)2Cu2Oy was studied in detail. Slow cooling was required for preparation of single phase T*-type compounds. After quenching,the samples contained Ce2Y2O7 as the major phase without T* structure presented. From room temperature to 1000℃ phase transition was not observed by thermal analysis. Upon slow cooling in oxygen, T*-type cuprates exhibited zero resistance at 30K.
1997, 46 (5): 981-985. doi: 10.7498/aps.46.981
We reported some 13C NMR experimental results in (DB18C6)KC60.The novel physical properties of this alkali mental fulleride show the magnetic ordering below 200K temperature and the enhancement of the resonant signals due to strong interaction between electron and nuclear.And the physical property of this material can be tuned dramatically by using supermolecular chemistry.
1997, 46 (5): 986-993. doi: 10.7498/aps.46.986
The phenomenological theory using in phase transition of crystalline state is generalized to polymers. The dielectric behaviors and space charge electret effects of polymers in the process of its structural transitions are explained by the theory. The phase transition of a crystal is the transition of its structure of first-order, it is related to the anomalous of dielectric constant εh of fast polarization. But the structural transitions of a polymer is only the transition of its structure of second-order and third-order; in this process, the anomalous of εh absents and the reciprocal of dielectric constant εl of slow polarization softens as parabolic type. The theory is in good agreement with experimental results of polypropylene.
Photoacoustic spectroscopy has been used to study nanoscaled SrTiO3 powder with different annealing temperature. The photoacoustic spectra show that the absorption edge of nanoscaled SrTiO3 powder has red shift with the rise of annealing temperature,which demonstrates that the energy gap becomes narrow. The decrease of energy gap is related to the growth of grains and the reduction of lattice parameter. In addition,the absorption band appeared around 700nm is induced by the transition of the captured electrons at the additional energy level of oxigen defects. The variation of the band is strongly dependent upon the sizes of the grains.
1997, 46 (5): 1001-1010. doi: 10.7498/aps.46.1001
We present a phenomenological model for the recombination of photoexcited carriers in quantum wells,which takes into account of the nonradiative recombination and the screening effect of free carriers in the wells.The results show,that the decay time of photoluminescence is strongly related to the sample quality,doping level,as well as the excitation intensity.
ELECTROLUMINESCENCE FROM NANOSCALE Si-PARTICLES EMBEDDED SiO2 FILMS DEPOSITED ON n+-Si AND p-Si SUBSTRATES
1997, 46 (5): 1011-1014. doi: 10.7498/aps.46.1011
The structures of Au/Si-rich SiO2/p-Si and Au/Si-rich SiO2/n+-Si have been fabricated and their electroluminescence characteristics have comparatively been studied. For the Au/Si-rich SiO2/p-Si structure, when the forward bias is more than 4V, red light is emitted, while under the reverse bias, no light is observed. For Au/Si-rich SiO2/n+-Si structure, it does not emit light under the forward bias, but it emits red light when the reverse bias is greater than 3.5V. The mechanism for electroluminescence from the Au/Si-rich SiO2/n+-Si structure is disscussed.
1997, 46 (5): 1015-1021. doi: 10.7498/aps.46.1015
A theoretical method to obtain the soft X-ray multilayer monochromater of-better energy resolution is put forward. The basic point is to choose the alternating elements with new criterions instead of general choosing method of high-and low z elements. Moreover, a simple and practicable multilayer designing method to achieve high reflectivity was presented. The some results of soft X-ray multilayer monochromater study in recent years on Beijing Synchrotron Radiation Facility (BSRF) have been given out.
INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
1997, 46 (5): 1022-1027. doi: 10.7498/aps.46.1022
In this paper, CH3CSNH2 passivated GaAs(100) surfaces in different conditions such as in alkali and acid solution were investigated by SRPES and PL. SRPES reveals that sulfur bonds both Ga and As on GaAs surfaces. Improvements of PL intensities reveal the reduction of surface combination velocity, resulting in the reduction of surface defect states due to the formation of sulfur passivation films.
ROTATING WAVES IN EXCITABLE MEDIA DESCRIBED-BY SIMPLIFIED HODGKIN-HUXLEY REACTION DIFFUSION EQUATION
1997, 46 (5): 1028-1035. doi: 10.7498/aps.46.1028
The rotating waves are obtained numerically in a specified model described by the simplified Hodgkin-Huxley reaction-diffusion equation under certain initial and boundary conditions.According to the characteristics of excitable media,the model is approximated to some simpler forms,from which qualitative analysis can be made in order to explore the reason of appearance of rotating waves
GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS
The Hawking-Unruh effect can be regarded as the compensate effect under energy-scale transformation or under time-scale transformation.The temperature appears as a pure gauge potential of the compensate field, and the state of affairs reflects the change of the zero point of vacuum energy.The Hawking-Unruh effect is a part of the inertial effect.The inertial effect originates from the variance of vacuum caused by acceleration.