Table of contents

The most complete harmonic coordinates for Kerr metric, which include the previous results as special cases, are given. It correctly reduces to the flat space-time metric at infinity or when both mass and angular momentum vanish, and to the complete Schwarzschild metric when only the angular momentum is zero.

The simplest imaginable ratchet system which cantains two noises correlated with each other is discussed. It is found that (1) the correlation between noises can induce transport, even when the ratchet potential is completely symmetric in space and the driving forcing is symmetric in time, and (2) the system can exhibit a current in either direction, and the direction can be controlled by the intensity of the correlation between noises.

Within the framework of the two-center shell model, the classically dynamical behaviour of a nucleon in heavy nuclei is investigated when nuclear shape parameters are changed systematically. It is found that there is a good quantum-classical correspondence of nucleonic regular (chaotic) motion so that Bohigas, Giannoni and Schmit conjecture is confirmed once again.

By perturbative calculations of the high temperature ground-state axial current in intrinsic regularization, an anomalous Chern-Simons topological mass term is induced in the three-dimensional effective action. The anomaly in three dimensions appears just in the ground-state current rather than in the divergence of ground-state current. In the abelian case, the contribution comes only from the vacuum polarization graph, whereas in the nonabelian case, contributions come from the vacuum polarization graph and the two triangle graphs.

In axially symmetric nuclei, three forms of paired states can be constructed, i.e., monopole pair, signature pair and ±Ω pair, which are the eigenstates of (J², J_z), (J_z², R_x(π)), and J_z, respectively. In the cranked shell model, though the energy spectra at ω = 0 are the same for three types of pair interactions, the spectra and spin alignments for ω ≠ 0 are different to a certain extent. It is found that the ω variation of the pair transfer amplitude, particularly the diabolic pair transfer, is quite different for different pair interactions.

Binary fluorozirconate glass ZrF₄· BaF₂ has been studied by molecular dynamical simulation using parameter-free Gordon-Kim potentials. In these simulations a novel technique is employed to monitor the motion of ions, thus the structure pictures of glass and the microscopic motion mechanism of ionic conduction are clearly and directly obtained. The glass networks commonly are formed by ZrF₈, ZrF₇ or ZrF₆ polyhedra, cross linked by Ba-F ionic bonds. The mean distance of the ionic nearest neighboring at 300 K is about 3.90 Å (Zr-Zr), 3.87 Å (Zr-Ba), and 1.96 Å (Zr-F). The two stronger peaks of five main peaks of vibrational spectra are at about 540-600 and 460-510 cm^-1 and three weaker peaks at about 386-416, 322-348, and 183-196 cm^-1. The other properties of glass: density, thermal expansion coefficient, polarization, and glass transition temperature are also examined.

The nonrelativistic energies of the core-excited 1s2snp⁴P (n = 2, 3, 4, 5) states for the lithium isoelectronic sequence from Be II to O VI are calculated with a full core plus correlation method using multiconfiguration interaction wavefunctions. The relativistic and mass-polarization effects on the energy are evaluated as the first order perturbation theory. Our predicted energies are lower than other theoretical results. They show that this full core plus correlation method is useful for the core-excited systems.

In a recent letter [L. Journel et al., Phys. Rev. Lett. 76, 30 (1996)], first experimental determination of the partial photoionization cross sections of lithium near the hollow atomic states was reported. Very extensive R-matrix calculation has also been carried out for the 'nl" ²P⁰ hollow states and assignments for the excited states have been made. However, these assignments are substantially different from those of other theoretical methods. This points out the need for more information and discussion which are necessary for a meaningful comparison.

Based on the realization of magneto-optical trap for cesium atom in China, great improvement is achieved on its performance. In the new experimental setup, a laser battery in stepwise injection-locking scheme is developed as laser source, which has more output power and better beam quality than the previous one. Under the optimum working condition, cesium atoms of more than 10⁹ with the density of 10¹¹ atoms/cm³ are trapped to form an atomic cloud with the diameter of 3 mm. Compared with previous results, both the number of trapped atoms and the density of atomic cloud are increased in two orders of magnitude.

Based on a simple consideration, the kick approximation used by Sundaram et al. in describing the interactions between super intense laser field and single atom is modified. Two different phase factors of the two kicks during one optical period are considered. It is found that we can introduce the factors in a very simple way and derive a new map which can be written in a closed form, and that to include these factors really improves the dynamical description of the system.

The valence electron binding energy spectra and orbital electron momentum distributions of ethane(C₂H₆) have been measured by high resolution (ΔE = 0.9 eV, Δp = 0.1 a.u.) symmetric non-coplanar electron momentum spectroscopy, at an impact energy of 1200eV+binding energy. The high energy resolution is adequate for us to be observe clearly the separated valence orbitals of C₂H₆.

We have demonstrated a diode-pumped Nd:YVO₄ laser that produced 273mW cw output at 671nm by using KTP intracavity doubling. The optical-optical efficiency of the all-solid-state red laser was 5.1%. The maximum output power of the fundamental wave at 1342 nm from Nd:YVO₄ was 2.3W with slope-efficiency of 43%.

The intensity response of an optically erased photorefractive two-wave mixing to the erase beam is studied by using the coupling wave equation and the band-transport model. The concepts of response strength and the minimum response intensity are introduced and their temperature dependence is investigated. A 2-fold increase in the response strength and 4-fold decrease in minimum response intensity have been experimentally observed in Ce:KNSBN at 633 nm when the crystal temperature is raised from 320 to 370 K. These experimental results are in agreement with theoretical analysis and show that the response property can be improved by changing the crystal temperature.

For a photorefractive crystal, the exponential gain coefficient of two-wave coupling, Γ, is a constant. In this paper, the constant Γ of a LiNbO₃:Fe crystal is measured by using Gaussian beams and quasi-uniform beams. The difference between the results is attributed to the self-defocusing effect of the crystal.

Theoretical and experimental investigation on the applied electric field- and intensity-dependent photorefractive response in a photorefractive polymeric composite is presented. The decay time constant and the corresponding grating-amplitude for the composite consisting of 1-n-butoxyl-2,5-dimethyl-4-(4'-nitrophenylazo)benzene: poly(N-vinylcarbazole): 2,4,7-trinitro-9-fluorenone with a weight ratio 44:55:1 were measured. The results revealed that there existed two gratings simultaneously, one was caused by the photorefractive effect, and the other was contributed from the photo-isomerization process. The dynamic process for the photorefractive grating was explained with a modified band transport model.

Excitation of slow electromagnetic waves for a configuration, in which a thin annular relativistic electron beam (TAREB) propagates through a cylindrical, dielectric-lined waveguide having a thin, annular plasma sheet at the same radial position as the TAREB, is studied in the presence of an infinite longitudinal guide magnetic field. Determinant dispersion equation is derived and directly numerically solved. The operation frequency and the growth rate of the waves are obtained and discussed.

Differential scanning calorimetry revealed a secondary transition at a lower temperature besides the order-disorder phase transition near 260 K in powders, not in single crystals, of C₆₀ from which solvents and impurities had been carefully excluded. This is attributed to phase transformation facilitated by nucleation around stacking faults. This proposal is supported by internal friction measurements on films, which confirmed the presence of this secondary transition, and by x-ray diffraction, which detected an hcp structure within the fcc lattice of C₆₀ at room temperature.

A new model of potential energy functions for atomic solids is given and applied to diamond and α-tin crystals. In the new model, a factor expressing the characters of covalent bonds has been included. Therefore it is suitable for covalent crystals. New potentials of C and α-Sn crystals accurately reproduce experimental elastic constants and phonon dispersion curves and so on. The set of new potentials is accurate enough for computer simulations.

By using Heine-Abarencov pseudopotential method with mono-parameter r_c, the expressions for ground state energy (r_s), pressure P (r_s), and bulk modulus B(r_s) of metallic hydrogen (fcc, bcc, and hcp structures) are derived. Based on Gibbs free energy function criterion, the calculation shows that cold metallic hydrogen lattice (T = 0K) belongs to hcp structure.

We present the calculation of the specific heat of helium II under pressure of 1 atm from very low temperature to approximately 1.8 K (the transition temperature T_λ = 2.712 K). Experimentally, the specific heat jumps from a finite value to infinity at T_λ. We have been able to reproduce the specific heat theoretically up to 1.8 K.

The electronic structure of fcc Fe/Cu {111} interface has been studied by angle-resolved photoemission with synchrotron radiation. The existence of the interface state and absence of intermixture between Fe and Cu atoms in the Fe/Cu {111} interface show that the Fe/Cu {111} system has an abrupt and ordered interface.

The influence of perimeter effects on dark I-V characteristics of GaAs diode is investigated experimentally. The results indicate that the diodes with high energy states density will be more easily shorted than that with low energy states density during alloying. The possibility of shunt short of GaAs diode increases with the decrease of the distance between the front contact and pn junction. The AlGaAs layers enhance the dark current.

Bi₂Sr_2-xLa_xCu₁O_6+δ (La-2201) thin films were successfully prepared on (100) SrTiO₃ and (100) LaAlO₃ substrates by in-situ dc-magnetron sputtering process. A series compensated 2201 targets of La³⁺ substitution contents for Sr²⁺ were studied for growing 2201 phase thin films. The superconducting zero resistance temperature T_c,0 reached 19 K. X-ray diffraction analyses showed that films oriented with c-axis perpendicular to the substrate surface and their lattice parameters are around 2.43-2.46 nm. Φ-scan and rocking curve show a good epitaxial growth and crystallisation of the films.

The effect of Cu doping in Pt spacer layers on the magneto-optical properties of sputtered Pt/Co multilayers has been investigated. It was found that the polar Kerr rotation θ_k, ellipticity _k, refractive index n and absorptive index k show an oscillation behavior as a function of the Cu content x, reflective index R keeps almost constant with the decreasing wavelength λ, three θ_k peaks appear at x = 0.03, 0.12, 0.25, respectively. Values of conductivity tensor σ_1xx, σ_2xx, σ_1xy, and σ_2xy in the PtCu layers have been derived from experimental θ_k, _k, n, and k values at wavelength 770 nm. The oscillation of the polar Kerr rotation θ_k may be resulted from spin polarized quantum size effects in the PtCu layers.

The preferred growth directions of Tb_0.3Dy_0.7Fe_1.95 grown by a super-high temperature gradient zone melting directional solidification technique were examined over a large range of the crystal growth velocity (0.5-30 mm/min). The [110] preferred growth direction was found in most case, and the [112] orientation only existed with a certain solidification condition. The magnetostriction of the [110] oriented samples was poor and had no obvious "stress effect", which exists in [110] perfect crystals according to calculation. The difference of the magnetostriction between the actual and perfect [110] oriented crystal was discussed in detail. The poor magnetostriction of the [110] oriented samples was attributed to the special 109.5° angular with two (111) twin growth mechanism, which resulted in the [114] direction along axis in twins, and only the [110] along axis in master.

Blue photoluminescence is observed in aged porous silicon samples anodized under Ar⁺ 488 nm laser illumination. No samples have been undergone any heating treatment process. Both nanosecond and microsecond decay of blue photoluminescence have been measured. Samples show a good monoexponential microsecond decay with lifetimes of about 5.3 μs. Photoluminescence excitation spectra of blue and red Photoluminescence indicate there is a large Stokes shift (about 800-900 meV) in the excitation spectra of red photoluminescence while no this marked Stokes shift in that of blue photoluminescence. The possible origin of the photoluminescence is discussed based on the experimental results.

The folding dynamics of a model of polypeptides is studied by Monte Carlo simulations. The effect of contacting probability between monomers is discussed. A specific temperature T* corresponding to the fastest folding process is found. At the temperature T*, the folding process appears more conservative than at other temperatures. In addition a cooperative characteristic, the length dependence of T*, is also illustrated. These show some instructive insights into the generic features of protein folding in nature.

Statistics of apparent collimation factors for molecular outflows catalogued is presented. Intrinsic collimation factor is calculated with the project effects removed. There is collimation difference between high and low mass outflows. It may concern the stellar sources in the flow regions, the outflow driving process, and the evolution time.