(Non-)anomalous D-brane and O-plane couplings: the normal bundle

The direct string computation of anomalous D-brane and orientifold plane couplings is extended to include the curvature of the normal bundle. The normalization of these terms is fixed unambiguously. New, non-anomalous gravitational couplings are found.     

Shaping nanoparticles and their optical spectra with photons

An experimental method to tailor the shape and the optical absorption spectra of metallic nanoparticles is presented. It exploits the influence of laser irradiation on particle growth by self-assembly of atoms deposited on a substrate surface. By applying nanosecond light pulses of appropriate fluence and three different wavelengths, oblate silver particles with three fixed axial ratios have been fabricated. Their optical extinction spectra were measured with s- and p-polarized light and are dominated by plasmon resonances at fixed photon energies determined by the axial ratio. Possible applications of such tailormade nanoclusters include catalytic converters and optical components with narrow-band extinction, the magnitude and center frequency of which can be specified in advance. Received: 9 September 1999 / Published online: 20 October 1999     

Surface Polaritons in a Wire Medium with Spatial Dispersion

The dispersion relations of the surface polariton in a semi-infinite wire medium with spatial dispersion are analysed. In comparison with the traditional spatial dispersive medium there only exists one branch instead of multibranch for the dispersion curve. The possibility of the experimentally observing the surface polaritons by attenuated total reflection is simulated numerically.     

Large-Quantity Synthesis of Single-Crystalline Metal Indium Nano/Sub-Micron Wires

Large quantities of metal indium single-crystalline wires with diameters ranging from tens of nanometres to a few micrometres were synthesized on Si substrates. Unlike traditional methods for the fabrication of nanowires or nanorods, liquid indium was squeezed out of the pores and cracks from porous an InAlN layer to form the wires. Continuous pushing out of liquid metal indium under strength, lowering of liquid-solid interfaces and the confinement of the cracks all contribute to the growth of indium wires. Our experiments have shed some light on the possibility of synthesizing large quantities quasi-1D nano/sub-micron structures with specified cross-sectional geometry using the similar method.     

Thickness Dependence of Resistivity and Optical Reflectance of ITO Films

Indium-tin-oxide （ITO） films deposited on crystalline silicon wafer and Corning glass are prepared by directcurrent magnetron sputtering method at room temperature with various thicknesses. The thickness dependences of structure, resistance and optical refectance of ITO films are characterized. The results show that when the film thickness is less than 40 nm, the resistivity and optical reflectance of the ITO film changes remarkably with thickness. The optoelectrical properties trend to stabilize when the thickness is over 55 nm. The GXRD result implies that the ITO film begins to crystallize if only the thickness is large enough.     

Non-Commutative Fock--Darwin System and Magnetic Field Limits

A Fock--Darwin system in noncommutative quantum mechanics is studied. By constructing Heisenberg algebra we obtain the levels on noncommutative space and noncommutative phase space, and give the corrections to the results in usual quantum mechanics. Moreover, to search the difference among the three spaces, the degeneracy is analysed by two ways, the valueof ω/ω_c and certain algebra realization (SU(2)and SU(1,1)), and some interesting properties in the magnetic field limit are exhibited, such as totally different degeneracy and magic number distribution for the given frequency or mass of a system in strong magnetic field.     

Enhanced Quantum Reflection of Ultracold Atoms with Strong Interatomic Interaction

We calculate the reflection probability for ultracold alkali atoms incident on a solid surface. By considering the interatomic interaction and using the WKB method, it is shown that the repulsive interaction between atoms has the effect of increasing the reflection probability. The increasing amplitude is related with the interatomic interaction and the depth of atom-surface potential. In addition, we also perform a numerical calculation to testify the effect of the interatomic interaction, and the analytic result is proven by the numerical result.     

Eigenvalue Problems of non-Hermitian Systems via Improved Asymptotic Iteration Method

We simply use the relation between the asymptotic iteration method and the Nikiforov-Uvarov method for the analytical solution of the second order linear ordinary differential equations. We apply this relation to study the Schroedinger equation with potentials admitting quasinormal modes. Non-Hermitian PT symmetric potentials have also been studied. Energy eigenvalues in all the cases by the relation are found to be consistent with exact results.     

Scheme for Direct Measurement of the Wigner Function via Resonant Interaction

We propose a scheme for direct measurement of the Wigner function for a cavity mode. In the scheme the cavity field resonantly interacts with an atomic ensemble. Under certain conditions, the state of the cavity mode is transferred to the atomic system. After a displacement the measurement of the parity of the atomic excitation number directly yields the Wigner function of the initial state of the cavity mode.     

Fluctuation of Mesoscopic RLC Circuit at Finite Temperature

We consider the fluctuation of mesoscopic RLC circuit at finite temperature since a resistance always produces Joule heat when the circuit is working. By virtue of the thermo field dynamics and the coherent thermo state representation we show that the quantum mechanical zero-point fluctuations of both charge and current increase with the rising temperature and the resistance value.