Vol. 44, No. 11 (1995)
THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
By mapping the spin 1/2 XXZ quantum chain to sine-Gordon model, we have analyzed the phase diagram of sine-Gordon model using tke method of gaussian wave functional and taking the large momentum cutoff. We have obtained the mas-sless region which agrees with the exact solution quite well.
ATOMIC AND MOLECULAR PHYSICS
1995, 44 (11): 1703-1711. doi: 10.7498/aps.44.1703
Electron-impact ionization cross sections for the 1s22s, 1s22p state of lithium-like aluminium are calculated by using distorted wave package, the inner-shell-exci-Cation-autoionization contribution is included in the final results. In this paper the electron-impact excitation cross sections and photoionization cross sections of the above two states are also given. It is shown that the ionization cross sections near threshold can joint smoothly with the corresponding excitation cross section and also meet the integrals of photoionization cross sections as the energy of the incidental electron become infinite.
1995, 44 (11): 1712-1718. doi: 10.7498/aps.44.1712
Dielectronic recombination may be regarded as a resonance radiative recombination process. In the process, an incident free electron with given kinetic energy collision with a ion A+q with charge +q, the free electron excited an bound electron of the ion A+q into nl state, and at the same time, itself be captured into another bound state nl, and a resonance doubly excited state will be formed. Furthermore, the state can be stable through radiative photons into some lower states. In this paper, we study the variation of Auger transition rates, radiative transition rates and dielectronic recombination rates with n in (1s1/2εp1/2)- (3s1/2np1/2)0- (n1 l1j1n2l2j2)1 recombination process using relativistic single configuration approximation method. From the method and program set up in this paper, any dielectronic recombination process for any ion can be calculated conveniently.
1995, 44 (11): 1719-1726. doi: 10.7498/aps.44.1719
Based on relativistic Born approximation theory, we have calculated the relati-vistic and non-relativistic generalized oscillator strengthes (GOS) of the Li-liks iso-electron sequence. The difference between the two calculations shows the relativistic effect of both the target and impact electron in the inelastic collision process. For low Z target (e.g. Li), the relativistic effect is negligible. For the 2s?p transition of Au+76, the relativistic GOS is 27.1% smaller than the non-relativistic one. At high impact energy, the contribution of transverse term of GOS to the differential cross section is important at certain angle. At extremely high impact energy (e.g. 106, 107eV), the transverse term of GOS becomes dominant at forward small angle and such forward peak makes overwhelming contribution to the totalinelastic cross section.
1995, 44 (11): 1727-1733. doi: 10.7498/aps.44.1727
Based on multiple-scattering self-consistent-field method, we have investigated the electron structrue of Co. cluster (n= 3-13). Comparing the calculated ioniza-tion potentials for different geometries and electron configurations with the experimental values, we can study the appropriate electron configuration and geometric structure of Co.. From the occupation of local 3d valence electron in configuration, we found, generally speaking, that the average atomic magnetic moment of Co clusters decreases as the number of atoms increases. From the geometry of cobalt clusters, we also surmise the various formation of Co. cluster.
CLASSICAL AREA OF PHENOMENOLOGY
1995, 44 (11): 1734-1746. doi: 10.7498/aps.44.1734
A comprehensive and self-consistent kinetics model of CuBr laser with hydrogen additives is presented. The radial distribution and time variation of population of the laser levels, laser power, gas temperature, electron temperature and density are described systematically. The results are compared with the experimental measurement.
1995, 44 (11): 1747-1753. doi: 10.7498/aps.44.1747
In this paper, we analyse the effect of space-charge wave in free-electron lasers from the single-particle model theory. A iterative computing method is presented. The calculations have shown that the first step solution of the couples of three waves in free-electron lasers is in accordance with the result obtained; the second order solution shows a more complex structure of the space-sharge wave.
1995, 44 (11): 1754-1760. doi: 10.7498/aps.44.1754
The measurement of nonlinear refractive index with Z-scan method for slow decay materials are discussed in detail. We derive the resultant electric field pattern at the aperture. It is pointed out that the accumulating effect contribute largely to the Z-scan signal in the slow decay nonlinear optical materials. The theoretical analysis is consistent with experimental result.
1995, 44 (11): 1761-1765. doi: 10.7498/aps.44.1761
Pulse shaping by two wave coupling in Ce doped KNSBN crystal is realized with a frequency-doubled CW modelocked Nd:YAG laser whose output pulsewidth is about 55ps. When the total incident intensity is higher than 10W/cm2, the shaping effect becomes more and more prominent with increasing incident intensity. The experimental results show good quantitative agreement with theory.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
1995, 44 (11): 1766-1775. doi: 10.7498/aps.44.1766
A statistical method for the ion configuration probability distribution in non-LTE plasmas based on the average-ion model is described. In this method, the ion configuration probabilities are obtained from the average level population probabilities of the ions according to the binomial distribution. The non-equilibrium ion configuration distribution and X-ray spectra emitted from Au plasmas produced by 1.06 μm laser are studied. The calculated X-ray emission spectra are in the same energy band range as the experimental results. We discuss the non-equilibrium characteristics of X-ray emission, and show that the contributions of the multiply excited ions to X-ray emission are important.
1995, 44 (11): 1776-1782. doi: 10.7498/aps.44.1776
The possibility and conditions of stochastic acceleration of an electron in plasma by a standing wave is discussed and numerically calculated. The analytical results show that the stochasticity of the motion of the electron is due to overlap of the two resonances imbedded in the interaction between the electron and the standing wave. The threshold of stochastic acceleration is evaluated analytically and numerically. The energy of stochastic acceleration of the electron is also calculated numerically with the trajectories of the electron being traced by using Poincare's surface-of-sectiun plot technique.
1995, 44 (11): 1783-1787. doi: 10.7498/aps.44.1783
The XUV spectra from AgXIX of laser-produced plasma are measured. The density dependence of △n= 0 (4-4) transitions from AgXIX has been studied in a density range 1017-1022 cm-3 with the collisional radiative model. The theoretical model included the effect of cascading from n= 5 states on the population of the n =4 levels. In addition, optical depth effects on the line intensities were considered. The two transitions of 4d2D5/2 4f2F7/2 and 4p2P3/2-4d2D5/2 remain close to each other and are unblended with other lines. Calculations of their radiation intensity ratio vs the electron density are performed. Electron density of laserproduced plasma has been deduced from the ratio.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
1995, 44 (11): 1788-1792. doi: 10.7498/aps.44.1788
A new X-ray powder diffraction method is reported to test phase depth distribution quantitatively and non-destructively. In case of the incident angle is larger than the total reflection critical angle, it is possible to quantitatively measure the polycrystalline phase depth profile in real scale. It can be used to the sample of continuous phase depth distribution. The method was verified with computer simulation and experiment of practical sample.
1995, 44 (11): 1793-1797. doi: 10.7498/aps.44.1793
A new method to extract X-ray polycrystalline diffraction patterns diffracted from different depth in real scale is pnesented. In this method the X-ray polycrystalline diffraction data of surface layer are collected at different incident angles, and then the X-ray diffraction patters diffracted from thin sheets at different depth are extracted directly by some special mathematical method. So the depth profiles of peak intensity, peak position and line profile can be obtained quantitatively and nondestrnctively. The algorithm was deduced in theory, and the feasibility of this method was primarily tested with a Ni/Mo film sample with prefered orientation. This method has the prospective application in the area of the thin films and its reactions, interface and surface processing studies.
1995, 44 (11): 1798-1804. doi: 10.7498/aps.44.1798
The calculation method of quantum chemistry has been extended to describe the lattice instabilities and the nature of the lattice instabilities of hexahalometallates. Some interesting calculation results have been obtained and compared with the exper-imental results obtained by Raman and Brillouin scattering.
1995, 44 (11): 1805-1813. doi: 10.7498/aps.44.1805
The dissociative adsorption of hydrogen molecule on (100), (110) and (111) surfaces of Ni, Pd and Cu are investigated using the embeded-atom method (EAM). First, the EAM potentials for H-metal surfaces are obtained by fitting the adsorption energies and the length of adsorption bond for single H atom on different surfaces of Ni, Pd and Cu. Then, the activation barriers Ea, adsorption heat q2d and corresponding H-metal bond length R for dissociation of H2 through various pathways are calculated. The potential energy contours for H2 dissociation on (110) surfaces of different metals are presented. The calculated results show that the dissociative adsorption of a hydrogen molecule depend on the species of substrate, the surface orientation and the dissociative pathways. The activation barrier for H2 dissociation on Nisurface is very low, while it is higher for H2 dissociation on Cu surface. The dissociative adsorption of H2 is easier on open (110) surface than that on close-packed(111) surfaces. Among the discussed dissociation pathways, it appears that the most favourable pathway for H2 is that from bridge site to the adjacent centre sites.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
INVESTIGATION OF ELECTRON PARAMAGNETIC RESONANCE PARAMETERS AND LATTICE IMPURITY IN Na_2ZnCl_4·3H_2O:Mn~(2+)
1995, 44 (11): 1814-1818. doi: 10.7498/aps.44.1814
In present paper, we proposed a new assumption that the O2- ion replaced the Cl- ion on the trigonal axis. On this basis, the EPR parameters D, a and gn were calculated. The results agree well with the experiments. The effects of uniaxial stress dD/dp and da/dp were also explained. This indicated that the assumption is reasonable.
1995, 44 (11): 1819-1824. doi: 10.7498/aps.44.1819
The ab-plane resistivity of Bi2Sr2CuO, crystals as a function of temperature has been measured. In the process of metal-insulator transition, the crystals at low temperature exhibit the two-dimensional weak localization behavior at first, and cross over to the variable-range-hopping conduction of the strong localization regime gradually. Discussions on the nature of the metal-insulator transition are presented based on the experimental results.
PEAK ENERGY FOCUSING OF PHOTOLUMINESCENCE FROM POROUS SILICON DURING STORING IN AIR OR 200℃ THERMAL OXIDATION
1995, 44 (11): 1825-1830. doi: 10.7498/aps.44.1825
Porous silicon (PS) samples with photoluminescence (PL) peak energies in the range of 1.4 to 2.0 eV were obtained by varing anodization conditions. 45 pieces of PS sample were stored in air for one year, and 102 pieces of PS sample were thermally oxidized at 200℃for 200 hours. After these two kinds of oxidation processes, PL peak energies of all PS samples focused to around 1.70-1.75eV. Supposing that luminescence centers with luminescence energies around 1.70-1.75eV exist in SiOx(x - 2) layers covering nanoscale silicon in fully oxidized PS, reported can be explained by the quantum confinement/luminescence centers model.
1995, 44 (11): 1831-1838. doi: 10.7498/aps.44.1831
Different interdiffusion characteristics between the Ag/YBCO and Al/YBCO contact interfaces have been revealed by SIMS studies. The different electrical properties of Ag/YBCO and Al/YBCO interfaces after high temperature treatment are well understood by SIMS results.
1995, 44 (11): 1839-1846. doi: 10.7498/aps.44.1839
A new type of cluster algorithm is developed to simulate the two-dimensional spin one half quantum Heisenberg antiferromagnet (QHAF) on a hexagonal lattice. The numerical results show that the method can be applied to study efficiently the QHAF systems at lowertemperatures, with large Trotter number, on the general bipartite lattices.
1995, 44 (11): 1847-1852. doi: 10.7498/aps.44.1847
perimental parameters is proposed in the present article. That the superiority of the suggested pulse sequence over the conventional two 90?echo sequence is confirmed by theoretical calculation and experimental results.
1995, 44 (11): 1853-1860. doi: 10.7498/aps.44.1853
With X-rays produced by protons exciting elemental and compound targets the mass attenuation coefficients have been systematicaJly measured for SiH4 in the range of X-ray energy 1.486-15.165keV, for Si in 8.041-29.109keV. Not only the validity of Bragg's additivity law in the gaseous compound was verifed by experiment, but also the mass attenuation coefficients of Si in the energy range 1.4-6 keV were obtained. The photoelectric cross sections have been obtained by subtracting thermal diffuse scattering and Compton scattering cross section from the measured total cross sections and compared with the theoretical results.
GROWTH OF METASTABLE fcc Mn THIN FILM ON GaAs(00l) AND ITS ELECTRONIC STRUCTURE STUDIED BY PHOTOEMISSION WITH SYNCHROTRON RADIATION
1995, 44 (11): 1861-1868. doi: 10.7498/aps.44.1861
The epitaxial growth of metastable fcc Mn thin films on GaAs(001) surface has been achieved at a substrate temperature of 400K. The development of the fcc Mn thin films as a function of coverage is studied by photoemission with synchrotron radiation. The electron density of states below the Fermi edge of the fcc Mn phase is measured A significant difference of the electronic structures is observed between the metastable fcc Mn phase and the thermodynamically stable α-Mn phase. Possible mechanisms are proposed to interprete the experimental result.