Vol. 42, No. 11 (1993)
1993-06-05
GENERAL
1993, 42 (11): 1719-1730.
doi: 10.7498/aps.42.1719
Abstract +
The Sato theory of KP and KdV hierarchies is generalized to the case of matrix lax operators , leading to new hierarchies of integrable nonlinear partial differential equations, which are called extended KP and KdV hierarchies in the context. It can be seen from the construction Process, the solutions of these new hierarchies can be expressed by the so-called quasi-wrongsky determinartes, and these quasi-wrongsky determinantes are just those obtained in ou recent study of 2-extended Toda field theories.
1993, 42 (11): 1731-1734.
doi: 10.7498/aps.42.1731
Abstract +
The deformation theory, in Ref [5],of travelling wave solutions to a generalized KdV equation is modified. The necessary and sufficient condition for a relevant algebraic equation to possess nonzero real root is presented and thus an error of analyses in Ref. [5] is pointe-dont. Finally an explicit formula of the solitary wave solutions generated by deformetion theory is obtained directly from the generalized KdV equation itselp.
1993, 42 (11): 1735-1740.
doi: 10.7498/aps.42.1735
Abstract +
This article presents numerical results on the distribution ol nearest-neighbor level spac-ings Shd the avoided crossing behavior of quanitum energy curves for a cpupled spin model coming from nuclear many body theory. When the system undergoes a transition from classical regular to chaos and then to regular as varying a model parameter,the Brody parameter of the level spacing distribution p(s) could be fairly associated to the fraction of classical chaotic tra-jectories in phase space.;ln the regime of parameters with large chaotic regions, a number of overlapping avoided crossings were discovered from the results of computations, Which lead the energy curves looked irregular These results are considered as quantum manifestation or ‘scars' pf classidal chaos in spectrum.
1993, 42 (11): 1741-1746.
doi: 10.7498/aps.42.1741
Abstract +
In order to reduce the critical slowing down in Monte Carlo simulations, a numerical study for the Ising model on 3-D random lattice using Swendsen-Wang algorithm is performed. The critical point obtained is βc=0. 075±0. 001. Moreover, to analyse the dynamical property of Swendsen-Wang method, the dynamical critical exponent z is estimated. The result is z =0. 74 ±0. 03. This indicates that the Swendsen-Wang method can greatly reduce the critical slowing down for the Ising model on 3-D random lattice.
NUCLEAR PHYSICS
1993, 42 (11): 1747-1755.
doi: 10.7498/aps.42.1747
Abstract +
The Hill-Wheeler formula is applied to deriving the equation of state for finite nuclei with the Gogny effective interaction in the framework of Hartree-Fock theory. The reasonable zero-temperature saturation properties is obtainde, and the critical temperature for liquid-gas phase transition of finite nuclei is found to be around 12 MeV. In addition it is found that the phenomenological formula for surface energy used widely is not available when the density is far away from the normal nuclear density, and a new formula is suggested.
ATOMIC AND MOLECULAR PHYSICS
1993, 42 (11): 1756-1761.
doi: 10.7498/aps.42.1756
Abstract +
A new method to study chemical adsorption kinetics by means of surface enhanced raman scattering is proposed. The theoretical model is proposed and experimental results given out. The adsorption of CV and PABA molecules on the surfaces of silver mirrors and silver colloids is studied. It is found that the adsorption of CV on silver surfaces is homogeneous, and the adsorption of PABA is heterogeneous. The differences of silver surfaces only influence the adsorption rate constant Ka, not changing the heterogeneity character of adsorption and desorp-tion rate constant (Kd=0). Finally, the significance of heterogeneity paramter is discussed.
1993, 42 (11): 1762-1765.
doi: 10.7498/aps.42.1762
Abstract +
In this paper, we calculate the radiation force on a two-level atom, whose levels are modulated by two far off resonance travelling wave fields, interacting with a near resonance travelling wave field. The results show that with appropriate conditions, the force can be much larger than spontaneous radiation force and then can be used in laser cooling with high efficiency.
1993, 42 (11): 1766-1773.
doi: 10.7498/aps.42.1766
Abstract +
Cesium molecules are pumped by a CW dye laser. Some of the excited molecules then pre-dissociate or collisionally transfer excitation to produce excited atoms at the 5D and 6P levels. The cross sections (in units of 10-14cm2) for the excitation transfer process Cs(6P)+Cs(5D) →Cs(7DJ)+Cs(6S)for J being 5/2 and 3/2 are 5. 4 ± 50% and 4. 9 ± 50%, respectively. The cross sections (in units of 10-14cm2) for the excitation transfer out of the 7D doublet [i. e. , Cs(7DJ)+Cs(6S) →states other than Cs(7D)] for J being 5/2 and 3/2 are 1. 6 ±50% and 0. 34±50%, respectively. To obtain these cross sections, the intensities of 7D and 5D fluorescence emissions and the 6P atom density are measured by using the absorption equivalent width technique. The results are discussed in eomparison with those of other experiments.
CLASSICAL AREA OF PHENOMENOLOGY
1993, 42 (11): 1774-1778.
doi: 10.7498/aps.42.1774
Abstract +
This paper describes, two kinds of high-light-intensity bulb, one is a mushroom-shaped bulb and the other is a round flat bulb, replacing the usual spherical bulb tor optical pumping. We light these two bulbs with a high r. f. source and carry out the experiments of pumping 87Rb maser with these lamps. The light intensities of the two bulbs are respectixely 2. 3 and 2 times as that of the spherical bulb. And the largest output powers of the maser pamped with these two lamps are-60 and -62 dBm at the optimum resonance cell temperature of 67 and 66℃ respectively. The improvement of short-term frequeney stability of the round flat bulb pumped 87Rb maser is consistent with the increment of the output power of the maser.
1993, 42 (11): 1779-1785.
doi: 10.7498/aps.42.1779
Abstract +
The radial distribution and time varidtion of gas temperature and atom density in a CuBr laser are obtained by using a consistent model and the experimental data of plasma electron temperature and density in the pulse period. The central tas temperature, the fluctuation of which is 300—500 K following the time change, is 1400—800 K. The gas atom density exhibits a concave profile in radial direction.
INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
1993, 42 (11): 1786-1792.
doi: 10.7498/aps.42.1786
Abstract +
The Raman spectra of two-component piezoelectric single crystal alumimium gallium phosphate A11-xGaxPO4(x=0.12) (AGP) have been obtained. and it has beeh shown that the red shifted spectrum lines exceed blue shifted ones in number and the TO/LO splittings for E modes decreases obviously in comparison with that of α-AlPO4. These features are interpreted in terms of lattice dynamics.
CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES
STUDY OF RAMAN SPECTRA FOR CRYSTALS WITH SPACE GROUP P3121(D34) ( Ⅱ )——THE RAMAN SPECTRA OF a-QUARTZ
1993, 42 (11): 1793-1799.
doi: 10.7498/aps.42.1793
Abstract +
Based on the symmetry of the space group P3121(D34), we consider that there are six molecules per primitive cell in a-quartz, and the constants of the primitive cell should be c = 1. 0788 nm and a = 0. 4904nm This point of view has been confirmed by our experiment.
1993, 42 (11): 1800-1805.
doi: 10.7498/aps.42.1800
Abstract +
The bimetallic layers of Co/Ti were deposited by ion beam sputtering on silicon implanted with arsenic. The sample of Co/Ti/Si was treated by a multi-step annealing under nitrogen ambient. The behaviuor of arsenic during the reaction of ternary Co/Ti/Si system was studied by Rutherford backscattering sepctrometry (RBS). The results show that a multi-layer structure of TiN(O)/Co-Ti-Si/CoSi2/Si was formed by the reaction and a number of arsenic atoms were segregated from silicon substrate to the interlayer of Co-Ti-Si compound.
1993, 42 (11): 1806-1811.
doi: 10.7498/aps.42.1806
Abstract +
The growth behavious of interfaces in order parametes-conservation system with spatial correlation are analysed by using renormalization-group method. The scaling exponentχ and dynamic exponent z are obtained as functions of spatial dimension d and roughening exponent ρ. The result shows that the conservation condition makes the fluctuation Propagation decay, and spatial correlations make the interface roughen. The results are also compared with that of E. Medina et al. and T. Sun et al.
1993, 42 (11): 1812-1816.
doi: 10.7498/aps.42.1812
Abstract +
The dynamics of a growing interface with an external field is investigated. The nontrivial fixed point is found and the exponents are calculated. The result shows that the external field tends to smoothen the interface and does not break the Galilean invariance.
1993, 42 (11): 1815-1821.
doi: 10.7498/aps.42.1815
Abstract +
The adsorption properties of hydrogen on the supported-metal surfaces are investigated using the Green function method within the framework of tight-binding approximation. The adsorption energy ΔE and the adatom state energy Ead, for hydrogen adsorption on Pt/ZnO, Cu/ZnO and Ni/ZnO composite systems are calculated by employing the self-consistent An-derson-Newns adsorption theory. The effects of the metal-support interaction on the adsorption properties of hydrogen on supported-metal surfaces are discussed. It is found that the stronger the metal-support interaction is, the less the adsorption energy and charge transfer for H on Pt(Cu,Ni)/ZnO become. The metal-support interaction impedes hydrogen adsorption on the metal surfaces. This effect becomes weak as the metal film grows thick.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
1993, 42 (11): 1822-1829.
doi: 10.7498/aps.42.1822
Abstract +
On the basis of multi-phonon transition theory, the origin of the fast component(100 fs) and the slow component (ns) in photo-excitation dynamics is explained and their evolution time is calculated. From these results, it is seen that the fast component is due to the formation of neutral bipolaron from free electron-hole pair, and the slow one is due to the non-radiative decay of bipolaron. The equations motion of the lattice are also integrated in real time to simulate the formation of bipolaron.
1993, 42 (11): 1830-1835.
doi: 10.7498/aps.42.1830
Abstract +
Deep levels of vacancy and substitutional impurity atoms in strained Si or Ge grown on alloy substrates are investigated. The band structures of strained bulk are calculated by using the empirical tight-binding method. The method of Green's function has been used to calculate the defect levels. The results show that the triplydegenerate p-like T2 level of defect in bulk Si or Ge splits into two levels due to the strain. The value of splitting increases with strain increasing. Owing to the strain,the valence band maximum of Si or Ge shifts upward, hence some deep levels in the bulk might transform to resonant ones.
1993, 42 (11): 1836-1844.
doi: 10.7498/aps.42.1836
Abstract +
The discrete variational method and embedded-cluster model within the framework of the two-component density functional theory and firstprinciple method are used to calculate the positron states of monovacancy in aluminum. The effect of the crystal field in which the cluster is embedded, magnitude of the cluster and frozen-core density approximation on the distribution of positron density and the positron annihilation characteristics are analyzed. The influence of the fully self-consistent scheme and the conventional scheme on the calculation of positron states in solids is discussed.
1993, 42 (11): 1845-1850.
doi: 10.7498/aps.42.1845
Abstract +
We develop a new type of cluster algorithm that strongly reduces the critical slowing down and the frustration effect in Monte Carlo simulations of the 2D quantum antiferro-magnet Heisenberg model (AFMH). The results obtained show that the method can be applied efficiently for the study of the 2D AFMH at lower temperatures.
1993, 42 (11): 1851-1855.
doi: 10.7498/aps.42.1851
Abstract +
This paper reports the study on the magnetic vicosity for chain-spherical Fe UFP prepared by laser pyrolysis. Fluctuation field,anisotropy and active volume of the particles were measured and calculated. The results show that the reverse magnetizing unit is made up of n chain spheres,and equivalent to a single-domain with uniaxial particle. Variation tendency of active volume of the particles is similiar to the acicular γ-type ferric oxide particles.
1993, 42 (11): 1856-1867.
doi: 10.7498/aps.42.1856
Abstract +
In this paper,the properties of the M?ssbauer effect resulting from supersonic solitons generated by the localized fluectuation and the deformation of structure in quasi-one-dimensional organic molecular crystal at temperature T≠0 and with non-linear vibration of molecular chains have been studied in the case of γ-photons emission from the γ-active nucleus. The expression for the time-dependentr γ radiation M?ssbauer transition probability is presented, and some interesting
1993, 42 (11): 1868-1873.
doi: 10.7498/aps.42.1868
Abstract +
The transmission spectra of p-PbTe have been measured by the strip-line technique with different far infrared laser wavelengths at different anhgles of the direction of maqnetic field relative to the crystal axis at low temperature of 1.5 k. A strong influence of mode coupling on strip-line transmission spectra has been observed and analyzed. The final results extracted from experimental spectra by numerical simulation are in good agreement with the six band k·p model calculation.
1993, 42 (11): 1874-1878.
doi: 10.7498/aps.42.1874
Abstract +
Luminescence spectra, picosecond decay and Fourier transform infrared spectroscopy measurements show that there are two independent emission mechanisms in the spontaneously oxidized porous Si. One is determined by the quantum confinement effect , the other is produced by the oxidation.
1993, 42 (11): 1879-1886.
doi: 10.7498/aps.42.1879
Abstract +
This paper reports the photoreflectance(PR) measurements of electric fields at the surface and the GaAs-GaAs interface of doped MBE GaAs films. By using alternatively He-Ne laser and He-Cd laser as pumping light, PR signals from the surface and the interface of the film can be effectively seperated the different penetration depth of different light. Electric fields at the surface and the interface were deduced from PR spectra. Film interference effects on modulation spectroscopy are studied. The origin of the electric field generated at interfaces are also discussed.
1993, 42 (11): 1887-1894.
doi: 10.7498/aps.42.1887
Abstract +
Collision cascades of 1 keV/atom gold clusters and 0. 2 keV/atom aluminum clusters impacting on gold targets have been investigated by moleculardynamics simulation. The spectra of gold recoil atoms are broader for cluster bombardment. The maximum recoil energies are nearly 2? times higher than the kinematic limit of mono-atomic bombardment. The multiple hits and the collisions between moving atoms make the recoil energies of target atoms increase. The energy transfer between two moving atoms are studied by conservation laws.
