Table of contents

The reconstruction of the atom-laser wave function is performed using an interferometric measurement with a standing-wave grating, and the results of this scheme are studied. The relations between the measurement data and the atomic wave function are also presented. This scheme is quite applicable and effectively avoids the initial random phase problem of the method that employs the laser running wave. The information which is encoded in the atom-laser wave is extracted.

A scheme of teleportation of a three-particle entangled state via entanglement swapping is proposed. It is shown that if a two-particle entangled state and a three-particle entangled state (both are not maximum entangled states) are used as quantum channels, probabilistic teleportation of the three-particle entangled state can be realized.

We show that bubbles of S²×S² can be created from vacuum fluctuation in the background de Sitter universes of k = 0, 1, so the space-time foam-like structure might really be constructed from bubbles of S²×S² in the very early inflating phase of our universe. Still, whether such a foam-like structure persisted during the later evolution of the universe is a problem unsolved at present.

We have reached a solution of the Dirac equation and the energy spectrum of electrons in the gravitational field of the Kerr-Newman black hole. The results are interesting in astrophysics for observations of the black hole.

A rotating gauge method is used to measure the span between two spheres with high precision in determination of the gravitational constant G. A rectangular gauge block slightly shorter than the span is located horizontally between two spheres, and the angle between two symmetric bounding points during rotation can be determined by measuring the shift of a laser beam passing through an optical plate fixed on the gauge block. Experimental results show that the uncertainty in the determination of the span between the two spheres is less than 0.5 µm.

The energy density for the central region in relativistic heavy-ion collisions can be estimated via the pseudorapidity distribution of transverse energy. The way to estimate the local energy density for the central region in relativistic heavy-ion collisions is proposed, in which only final state particles emitted from the same source are included. The energy density arrived at in the NA49 experiments is about 0.9 GeV/fm³.

Using the factorizable character of amplitudes for the double diffractive process in the Landshoff-Nachtmann model, we have discussed the inclusive glueball production in high-energy pp collisions via the fusion process of two non-perturbative gluons, and have compared it with the double diffractive alike process. We found that, as the c.m. energy E_cms increases from 20 to 20 000 GeV, the cross sections of the latter process are about one to two orders larger than the former. Such an outcome could be explained from the hypothesis of duality between glueballs and pomeron.

We calculate the contribution of vector meson dominance to deeply inelastic lepton-nucleon scattering in the kinematic region of the HERMES experiment. The results obtained show that this contribution is quite significant. Together with the fact that there exist very striking left-right asymmetries for hadrons produced in single-spin hadron-hadron collisions, these results imply that the single-spin azimuthal asymmetry observed by HERMES cannot be simply regarded as a pure fragmentation effect.

The density distributions of the last neutron in ²⁰⁹Pb were investigated by analysis of the ²⁰⁸Pb(d,p)²⁰⁹Pb transfer reactions at 8 MeV. The results show that the last neutron in the 2d_5/2,3s_1/2,1g_7/2 and 2d_3/2 states is present with appreciable probability at distances much larger than the core radius. Therefore, these states should be the neutron halo or skin states. Moreover, the density distributions extracted illustrate that there is an intrinsic relationship between the node number of state and the halo formation.

High-spin states in ¹²²Ba have been investigated in the ¹⁰⁷Ag(¹⁹F, 4n) reaction by in-beam γ-ray spectroscopic methods. The ground-state band has been observed with spin up to 20ℏ and a negative-parity band is identified with spin state up to 19ℏ. A band-crossing in the yrast band is observed at a rotational frequency of ℏω≈ 0.36 MeV and, in accordance with cranked shell model calculations, is interpreted as arising from the alignment of two h_11/2 protons. Strong E1 transitions between the negative-parity and the yrast bands have been observed, which are proposed as possible evidence for octupole correlations.

Static properties of Λ-hypernuclei are calculated self-consistently in the relativistic mean-field model. The effect of Λ on the core nucleons are investigated. It is found that the rms radii of the neutron become smaller than those of ordinary nuclei, when a closed-shell nuclear core is embedded in a 1s_1/2 Λ hyperon.

Measurements of the total reaction cross sections (σ_R) for some proton-rich nuclei (N = 11-15 isotones) on a carbon target at intermediate energies have been performed on the Radioactive Ion Beam Line of the Heavy Ion Research Facility in Lanzhou. A larger enhancement of σ_R for ²⁷P has been observed than for its neighbours. Evidence for a proton halo in ²⁷P has been revealed in the Glauber analysis of the total reaction cross sections in terms of the difference factor d.

Protons are emitted in a greater quantity in a neutron-deficient system ⁴⁰Ar+¹¹²Sn while triton emissions are greater in a neutron-rich system ⁴⁰Ar+¹²⁴Sn at an incident energy of 30 MeV/u. Similar to neutrons, proton emission provides a dominant contribution to neutralize the system N/Z in the decay process of the hot nuclei. The emission of hydrogen isotopes with high energies is much enhanced in the ¹¹²Sn system. The original temperature of the hot nuclei in the ⁴⁰Ar+¹¹²Sn reaction is 5.8±0.3 MeV, about 0.7 MeV higher than 5.1±0.3 MeV as in the ⁴⁰Ar+¹²⁴Sn reaction.

The entrance channel dependence of the isospin effects of nuclear stopping in intermediate energy heavy-ion collisions has been studied by using an isospin-dependent quantum molecular dynamics with three different kinds of symmetry potentials. It is shown that nuclear stopping is sensitive to the beam energy, the impact parameter and the mass of the colliding system, especially very sensitive to the isospin dependence of the in-medium nucleon-nucleon cross section, but insensitive to the symmetry potential and the neutron-to-proton ratio of the colliding system. From this investigation, it is proposed that nuclear stopping can be used as a new probe to extract the information on the isospin dependence of the in-medium nucleon-nucleon cross section in intermediate energy heavy-ion collisions.

The Monte Carlo generator (LUCIAE) is used to investigate the fluctuations of K/π ratios at super proton synchrotron energies. The distribution of K/π ratios seems to be Gaussian from the simulation and the distribution width, and the relative variances are larger than those from the Poissonian-type pure-statistical fluctuations. This discrepancy might be attributed to the dynamical fluctuations involved in the LUCIAE model.

Using the one-dimensional ion mode, we theoretically investigate the dynamics ionization process and the high-order harmonic generation of the He⁺ subject to different kinds of two-colour laser pulses with the same fundamental frequency but various harmonic frequencies. It is found that from the results calculated by numerically solving the time-dependent Schrödinger equation, the two-colour laser pulse with the fundamental and harmonic frequencies enables the power spectrum of high-order harmonic generation to increase by a few orders of magnitude and the yield of He²⁺ to enhance significantly when the harmonic frequency of the laser pulse is close to the energy interval between the ground state and the first excited state of He⁺; even the harmonic field added into the pulse is much weaker than the fundamental one.

With the method of wavelet transform, we consider the temporal behaviour of high-order harmonic generation from one-dimensional H₂⁺ exposed to an ultrashort laser pulse with a duration of tens of femtoseconds. The results, which are calculated by numerically solving the corresponding time-dependent Schrödinger equation with the split-operator method in the non-Born-Oppenheimer approach, show that: (1) the high-order harmonics in the cut-off range emitted as a train of pulses have better coherence than those in the plateau; (2) the harmonics are emitted early in time when the intensity of the laser pulse increases.

An empirical formula is proposed to describe the K-shell ionization cross sections by electron impact over a wide range of atomic numbers and overvoltages U (the ratio between the electron incident energy and the binding energy of the electrons in the K-shell). The study is based on the analysis of existing experimental data of K-shell ionization cross sections. The expression shows the results in good agreement with the data for Z<6 atoms as well as for 6⩽Z⩽79.

We have performed the photofragmentation studies of pristine C₆₀ and C₆₀/C₇₀ composites on the reflectron time-of-flight mass spectrometer (RTOF MS) in the positive and negative ion channels. The mechanism of the formation of daughter fullerenes in the negative ion channel and the enhancement of fullerene coalescence reactions have been discussed and compared to our previous studies on the linear TOF. The 5 cm free expansion path in the RTOF experiments provides sufficient time and a favourable environment for the electrons to attach to the neutral daughter species, so it is thought to play a key role for the appearance of strong mass peaks of anionic fragmentation and aggregation fullerene products. The appearance of odd-numbered ``fullerene'' fragments is briefly discussed.

The electronic structure of the C₂₀ cluster in monocyclic ring, bowl and fullerene isomers has been calculated using the tight-binding scheme developed by Harrison, starting in particular from the sp^2.803-hybrids for the fullerene structure. The study of energetics predicts the fullerene to be the ground state with the bowl and ring lying over 1.32 and 3.35 eV higher in energy. The total energies will be lowered by Peierls or Jahn-Teller distortion, but the energetic ordering remains unchanged. It is also shown that the range of valence electron, the level difference between the highest occupied molecular orbital and the lowest unoccupied molecular orbital as well as the σ-π gap, which are less sensitive to the exact geometry, vary in the ring, bowl and fullerene sequence.

We propose and experimentally investigate a new scheme capable of suppressing light-induced scattering by periodical incoherent erasure during every non-volatile holographic recording cycle in photochromic LiNbO₃:Fe:Mn crystals. The results demonstrate that the scattering noise is suppressed effectively, and the final diffraction efficiency of the fixed grating is significantly enhanced, rather than decreased, by about 30% compared with the conventional recording procedure. The period of the recording and incoherent erasure cycle is theoretically calculated and experimentally optimized.

We present a nonlinear theory of light velocity reduction in a three-level Λ system based on electromagnetically induced transparency. Analysis shows that the probe field propagates with a velocity that is quite strongly dependent on its intensity instead of being merely approximately dependent on the coupling intensity. Moreover, the minimum group velocity of the probe field is analytically given for a given input power.

When an atom moves in an optical cavity, the total momentum of the atom does not remain constant. We study a two-level atom moving slowly in an optical cavity, and give the time dependence of its mean momentum. It is found that when the initial momentum of the atom is larger than that of the photon, the mean momentum oscillates around a value less than the initial value. But, if the initial momentum is less than the momentum of the photon, the mean momentum of the atom is greater than its initial value in most cases.

A scheme is proposed for generating the superpositions of several coherent states in a cavity field with dispersive cavity quantum electrodynamics (QED). In the scheme, a sequence of atoms interacts dispersively with the cavity field, connected with a microwave source, and is manipulated by classical fields, followed by state-selective measurements. In this way, the cavity field is collapsed onto a superposition of several coherent states along a straight line with controllable coefficients. This scheme provides the possibility for quantum state engineering via coherent-state superpositions in cavity QED for the first time.

The axis of the integrated superluminescent light source was tilted with respect to the output facet normal for lasing suppression. A new phenomenon (lasing suppression) was observed in the tilted integrated device. Three new schemes were proposed and demonstrated further to suppress the lasing by analysing the reason for lasing in the tilted structure. The lasing was suppressed successfully at high pumping levels, and high superluminescent powers (more than 300 mW) were obtained at a pulsed condition with the spectral full width at half maximum of 25-30 nm.

Optical limiting properties of a crystal violet cation fulleride salt dissolved in tetrahydrofuran have been studied by using 10 ns, 532 nm laser pulses. The fluence-dependent transmissivity measurements were performed on the samples with the same concentration and different path lengths in a collimated optical set-up. For comparison, the fluence-dependent transmissivities of fullerene C₆₀ and crystal violet solutions were also measured under the same linear transmissivity. The nonlinear optical limiting effect of the fulleride salt in tetrahydrofuran was even slightly stronger than that of C₆₀ in toluene.

A special prism coupling technique with the KBe₂BO₃F₂ crystal is adopted to produce deep ultraviolet light including the fourth harmonic from an Nd:YAG laser, for which a conversion efficiency as high as 10% has been obtained.

We demonstrate theoretically that two-dimensional photonic bandgap materials are indeed perfect polarizers provided that they have a proper photonic band structure along the incident direction of light. This kind of polarizer is fundamentally different from conventional ones. It can function in a wide frequency range with high performance and its size can be made very compact, which renders it useful as a micropolarizer in micro-optics.

In the parabolic and quasi-linear approximations, a theoretical description for the acoustical parametric field from a focusing source after inserting a sample is derived by using the superposition method of Gaussian beams. This model takes into consideration the attenuation, diffraction and nonlinear effects. The numerical computations of the axial sound pressure amplitude curves for the difference frequency sounds after the insertion of a sample are presented. The results indicate that this new model can be extended to measure or image the nonlinear parameter in the focused field.

Considering the variation of dust charges, we have analytically studied the governing equation for the system with the same model as that for cold dust acoustic waves in a demagnetized plasma but with the contribution of hot dust. The result indicates that the governing equation is also a Kortweg-de Vries equation, although its amplitude and width will be smaller compared with the cold dust case.

Electron heat diffusivity inferred from the electron power balance was studied in the ohmically heated plasma on an HT-7 tokamak. The results obtained before and after siliconization were compared and it is found that the diffusivity is reduced obviously in the half of the outer region (r/a>0.5) after siliconization, which was the reason why energy confinement was improved after siliconization.

The effects of three factors, including the power supply, the arc behaviour in the arc channel and the fluid dynamic process of the jet, on a plasma spraying jet have been experimentally detected by means of spectroscopic diagnostic techniques. The fast Fourier transform method has been applied to the analysis of the arc voltage and spectral line intensity of the jet. The three factors have been studied and distinguished from each other.

The propagation of a laser pulse with a peak intensity 10¹⁹ W/cm² through the preformed underdense plasma with the density 0.014n_c are studied by using two-dimensional particle-in-cell simulations. The longitudinal electron heating is identified and verified, and its major property agrees with the theoretical prediction. The electron distributions in phase space, patterns of the electric fields, profiles of the ion or electron density and other plasma nonlinear phenomena are presented and discussed.

A helicon mode discharge is realized in a newly erected set-up and two jumps are observed in the variation of the plasma density with the controlled magnetic field, which is a typical characteristic of the helicon mode discharge. A reasonable explanation is proposed for the appearance of the density jumps. The helicon wavelength is evaluated to be about 20 cm and it is nearly constant in the helicon mode discharge. The density obtained is nearly up to 3.5×10¹⁸m^-3 with only 0.5 Pa argon pressure and 300 W radio frequency power supply, and it is more than one magnitude higher than that in other discharges at comparable pressures and input powers. The electron temperature is found to increase as the pressure is decreased.

The turbulent particle and thermal transport scaling laws are derived by means of the Lagrangian invariant of trapped electron dynamics in tokamaks, which are in good agreement with experimental results. On the basis of two scaling laws, it is proposed that the optimization of electron density and temperature profiles can be achieved by designing a desirable safety factor profile.

The performance and characteristics of a cathodic arc plasma source, consisting of a titanium cathode, an anode with and without a tungsten mesh, and a coil producing a focusing magnetic field between the anode and cathode, are investigated. The high transparency and large area of the mesh allow a high plasma flux to penetrate the anode from the cathodic arc. The mesh helps to decrease the arc resistance and the ignition voltage of the cathodic arc in the focusing magnetic field, and to increase the life of the source, which means that the source makes the cathodic arc easily and greatly stabilized during the operation when a focusing magnetic field exists in the source.

The electronic localization lengths λ of metallic carbon nanotubes with different chiral symmetries have been calculated by one parameter scaling method. It is found that λ is independent of the nanotube chirality, but depends linearly on the diameter. The dependence of λ on the disorder strength W has also been studied, and a power-law relation between λ and W is also found to be independent of the tube chirality. Our numerical results are in good agreement with recent experimental observations and other theoretical results for only the ``armchair'' nanotubes.

The electrical properties of a type of semiconductor heterostructure fabricated by depositing zinc oxide film on a silicon substrate are investigated. The I-V, I-T curves, and deep level transient spectra are measured. From these results, we acquire the information of the characteristics of the junction, and compute some energy levels of the samples.

We present a local density functional calculation of the effect of an external electric field on the work function change of Pd and Ag adsorption on an Al(001) surface. The adsorption of K has also been considered for comparison. We found that the work functions for all the systems increased linearly when the strength of the external electric field was increased. Since the polarized electrons at the interstitial regions between the adsorbate and substrate for Pd/Al(001) and Ag/Al(001) react to the external electric field differently, the subtle differences between Pd/Al(001) and Ag/Al(001) bondings has been characterized through the comparison of the slopes of the work function change versus electric field.

A large magnetic entropy change about twice as high as that of pure gadolinium metal near room temperature has been discovered in manganese perovskites La_0.837Ca_0.098Na_0.038Mn_0.987O_3.00(8.3 J·kg^-1·K^-1, at 256 K) and La_0.822Ca_0.096K_0.043Mn_0.974O_3.00 (6.8 J·kg^-1·K^-1, at 265 K) under a magnetic field of 1.5 T. This phenomenon indicates that manganese perovskites have potential applications for magnetic refrigerants in an extended temperature range even near room temperature.

The influence of interfaces on the magneto-optical Kerr effect in the Co/Ni multilayer has been investigated. It was found that the magnetic-optical Kerr rotation varies with the numbers of interfaces (x) in the Co/Ni multilayer, which indicated that the interface states play an important role in the Kerr effect. Moreover, ellipticity and optical constants n and k are also found to vary with x. Some possible mechanisms have been discussed.

Two new organic dye samples J and L with a large two-photon absorption (TPA) cross section have been reported. The linear absorption spectra show that there is no linear absorption at the wavelength from 650 to 1200 nm. The molecular TPA cross section was measured to be as high as 2.59×10^-47 cm⁴·s and 2.98×10^-47 cm⁴·s at 1064 nm for samples J and L, respectively. The input-output curves indicate that there is a clear optical power limiting behaviour when the input intensity is higher than 0.4 GW/cm². Furthermore, the basic theory of the TPA process has been discussed.

Crystalline SiC samples were prepared in solidification of silicon melt saturated by carbon solved from the inner wall of a graphite crucible. The crystalline structure of the samples was analysed in Raman spectroscopy and confirmed as 3C-SiC both in x-ray diffraction and x-ray photoelectron spectroscopy (XPS). The Raman spectra of the samples present a strong sharp peak located at 796.3 cm^-1 with a full width at half maximum about 6 cm^-1 and three weak peaks broadened around 1525.6, 1631.4 and 1719.1 cm^-1, respectively. The former belongs to the transverse optical phonons of 3C-SiC, while the latter can be attributed to the second-order scattering. However, the longitudinal optical mode of 3C-SiC has not been found for our samples. An additional broadened peak at 532.2 cm^-1 may imply the existence of some lattice defect in the samples, which is related to nitrogen introduced unintentionally into the lattice in the growth process and confirmed in XPS of N 1s binding energy centred at 400.9 eV.

Single bubble sonoluminescence (SBSL) flashes have been steadily upscaled by a sinusoidal wave with a pulse at each cycle at some suitable phase position, which proves the prediction of the spiking SBSL suggested by Moss et al. [Phys. Lett. A 211(1996)69]. Based on the Rayleigh-Plesset bubble dynamics, the numerical simulations show a very qualitative agreement with those measured in experiment.

Using a photonic band calculation method, we calculate the effective dielectric function of an array of carbon nanotubes which have a simple equivalent isotropic dielectric function. The results for the equivalent dielectric function and for the local graphite-like dielectric tensor are found to be almost the same. Taking a fixed outer diameter of the nanotubes to be 10 nm and a fixed distance between them to be 10.3 nm, we investigate the effect of the hollow core and found that it is important that the ratio of the inner to the outer radii is approximately larger than 0.3. By taking a large ratio of 0.58, the theoretical results are improved greatly and can describe the experimental data very well.

Nanostructured carbon thin films on Si tips were prepared by hot filament chemical vapour deposition at different substrate temperatures. The Si tips and films were obtained under various deposition conditions in the same reaction chamber. It was found that the field emission properties from graphite-like nanostructured carbon on Si tips were greatly improved, compared with those of nanodiamond films on Si tips. A turn-on field of 1.2 V·cm^-1 was observed for high sp² content thin films on Si tips. The analysis showed that the field emission enhancement effect was caused by the tip geometry, tunnel effect and sp² content in the films. However, the geometrical enhancement was greater than that of the tunnel and sp² content effects.

Based on corrected rate equations, the kinetics is revealed for the initial growth of thin films with a low nucleus density and a linear lateral growth rate on a substrate surface. In this case, the mobility and coalescence terms in the rate equations are neglected, and the coverage term takes a dominant role. All the calculated results are in agreement with experimental data. These results introduce a new scaling in the case of dominant coverage, which is different from the those in the case of coalescence or mobility in a dominant role.

Diamond deposition at low temperatures is investigated and the relationship between substrate temperature for diamond growth and the energy of the carbonaceous species is given. The electron energy distribution and velocity distribution during the electron assisted chemical vapour deposition have been obtained by using Monte Carlo simulation. The main results obtained are as follows. (1) The substrate temperature for diamond growth will be lower than 800°C when the carbonaceous species on the substrate have mobility energy. For example, if the energy of the carbonaceous species is 0.75 eV, the substrate temperature will be 380°C-600°C. (2) The great number of atomic H on the substrate is of importance to the growth of diamond films.

The specific features of current variation during different stages of the microarc oxidation process were studied on the timescale. The cathodic current was found to be closely related to the microarc discharge. The discharge was responsible for the formation of a dense coating with unique physical characteristics. A method for obtaining high-quality coating has been discussed.

It is found that the doping of cerium ion into anatase TiO₂ can improve the electrorheological (ER) effects of TiO₂ and broaden the operational temperature range. Especially, the substitution of 7-11 mol% of the cerium dopant for Ti can obtain a relatively high shear stress, τ = 7.4 kPa (at 4 kV/mm), which is ten times larger than that of pure TiO₂ ER fluid. Also, the typical Ce-doped TiO₂ ER fluid shows the highest shear stress at 80°C, but 40°C for pure TiO₂ ER fluid. The dielectric loss and dielectric constant at a low frequency of TiO₂ is improved by the doping of cerium, and the temperature dependence of the dielectric properties shows an obvious difference between pure and doped TiO₂ ER fluids. These can well explain the ER behaviour of doped TiO₂. Furthermore, the change of rheological and dielectric properties is discussed on the basis of the lattice distortion and defects in TiO₂ arising from the doping of cerium.

A functional field effect transistor with self-organized In_0.15Ga_0.85As/GaAs quantum wires (QWRs) as a channel was achieved by molecular beam epitaxy on a (553)B GaAs substrate. Both the three-dimensional image of atomic force microscopy and the polarization of the photoluminance peaks reveal that the channel of the device is a self-organized QWR structure. The device with a gate length of 2 µm and a source-drain spacing of 5 µm performed a good enhancement-mode characteristic and a maximum transconductance of 65 mS/mm was obtained at the gate voltage of 1.0 V by the geometric gate width at room temperature. The saturated drain current is as high as 5.6 mA. The device exhibited a much larger current capacity due to the high density of the self-organized QWRs in its channel layer. In addition, the effective gate width was discussed in comparison with the geometric gate width of the device, from which a larger maximum transconductance of 130 mS/mm could be estimated.

The evolution characteristics and energy extraction of a rotating black hole are investigated by considering the magnetic coupling with the surrounding accretion disc. It is found that both the mass and spin of the black hole might be reduced by the joint effects of disc accretion and magnetic coupling, provided that the latter is stronger than the former. The efficiencies of the two energy mechanisms are calculated and compared to a variety of parameters. In addition, the validity of the laws of black hole thermodynamics is discussed.

Assuming an adiabatic evolution of a gamma-ray burst (GRB) fireball interacting with an external medium, we calculate the hydrodynamics of the fireball with an energy injection from a strongly magnetic millisecond pulsar through magnetic dipole radiation, and obtain the light curve of the optical afterglow from the fireball by synchrotron radiation. The results are given both for an homogeneous external medium and for a wind ejected by GRB progenitor. Our calculations are also available in both ultra-relativistic and non-relativistic phases. Furthermore, the observed R-band light curve of GRB000301C can be well fitted in our model, which might provide a probe of the properties of GRB progenitors.