The problem of the isotopic harmonic oscillator of time-dependent frequency confined in a spherical box with time-dependent radius is studied. We show that the exact solution and the Lewis invariant operator can be obtained by performing two consecutive gauge transformations on the time-dependent Schr?dinger equation. On the basis of the exact solution the non-adiabatic Berry phases for the system are calculated.

A new class of nonlinear Lie algebra has been found, which is generated naturally by the Hamiltonian operator, the square of the angular momentum operator and the ladder operator for the central potentials. According to the theory of nonlinear Lie algebra, without using the factorization method, we obtained the vector ladder operators for the three-dimensional isotropic harmonic oscillator and hydrogen atom. The radial components of these operators, which are independent of the quantum numbers, are just the radial ladder operators for the same potentials.

The domain structures of Pt_{1-x}Cu_{x}/Co multilayer films in as-grown and remanent states have been investigated by using magnetic force microscope. The magnetic domain patterns are strongly influenced by the Cu concentration. For pure Pt/Co multilayer in as-grown state, its domain pattern is depicted as island-like one; however, with the Cu doped in Pt spacer layers, the doman patterns become dot-like, but the island-like domain pattern appears again for the Cu concentration of 14 at%. The domain patterns variation can be attributed to the change of effective perpendicular anisotropy K_{ueff} due to the effect of Cu atom doped in the Pt spacer layers. Besides, the domain structures of Pt/Co multilayer films in remanent state after the application of various perpendicular magnetic fields have also been studied.

Guo Zhong-yan, Zhan Wen-long, Liu Guan-hua, Sun Zhi-yu, Xiao Guo-qing, Jiang Shan-hong, Li Jia-xing, Wang Jin-chuan, Meng Xiang-wei, Zhang Wan-sheng, Qin Li-jun, Wang Quan-jin

Chin. Phys. B 1999, 8 (1): 021; doi: 10.1088/1004-423X/8/1/004
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The Bρ-ΔE-Bρ-TOF techniques used for the identification and separation of radioactive nuclear beams (RNB) at RIBLL, are described. As a PF-type radioactive nuclear beam line, RIBLL can deliver RNB with high purity for light projectiles by using Bρ-ΔE-Bρ techniques, while for heavy ones, the Bρ-ΔE-Bρ-TOF methods must be adopted in order to identify the RNB clearly.

The acoustic-energy loss was measured when the sound wave propagated through a layer of water fog. By the application of the sound attenuation theory in granular media and by means of the acoustic inverse (optimization) method, the size-distribution of the drops and the moisture content in the water fog were measured. It is demonstrated that the sizes of the water drops obey the normal distribution approximately. Comparison of the size-distribution results between data obtained by the inverse measurements and those obtained by the optic-microscopic-size methods shows good agreement with each other. The results of the moisture content and the thickness of the fog layers obtained by this method are also consistent with the results measured by other methods (for example, the water-content weight and the direct measurement of layer's thickness by a scale, etc.) reasonably.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

In low density (～10^{18} cm^{-3}) plasmas sustained by lower hybrid current drive in the high magnetic field superconducting tokamak Triam-1M (Kyushu University, Japan), high ion temperature has been frequently observed by an NEA diagnostic. The experimental phenomena are briefly described and analyzed in the paper. It is suggested by the analysis that the high ion temperature of the low density tokamak plasmas is attributed to ion Landau damping of lower hybrid wave.

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

We have prepared nearly monodisperse CdSe nanocrystallites with diameters of 1-4 nm from the rapid pyrolysis of organometallic precursors in a hot coordinating solvent. The nanocrystal structures have been characterized by transmission electron microscopy and electron diffraction. From the absorption spectrum, we have observed the prominent peak of 1S-1S excitonic transition, which is obviously blue-shifted from the bulk bandgap and the largest shift is about 1.25 eV. We have used a theoretical model based on the tight binding approximation to analyze the quantum size effect of these nanocrystallites. The results have been compared with those of the effective mass approximation model.

Using the scattering-theoretic method and employing the nearest-neighbor tight-binding formalism to describe the bulk electronic structure, we have studied the electronic structure of Si(337) surface. The wave-vector-resolved layer densities of states are presented. The results show that there are six surface bound states in the range from -12.0 to 2.0 eV. Some properties of these surface states are discussed.

The quantum infinite range XY spin glass model with the infinite range planar Dzyaloshinskii-Moriya interaction in external field for spin S=1/2 is investigated theoretically. Numerical calculations show that, the specific heat depending on the temperature has crossover behavior; the weak field dependence of the specific heat can be fitted by the parabolic approximation, C/T=A+Bh^{2}, the coefficient B is peaked near the transition point.

Nanocrystalline V_{2}O_{5} thin films were reactively radio-frequency magnetron-sputtered under optimal deposition parameters. Their electrochemical and electrochromic characteristics were investigated by cyclic voltammetry and in-situ monochromatic transmittance measurements. Upon lithium intercalation, V_{2}O_{5} thin films showed a double electrochromic behavior depending on the wavelength and the intercalation extent. X-ray photoelectron spectroscopy results showed that part of the V^{5+} in V_{2}O_{5} was reduced to V^{4+} during the Li^{+} intercalation process.

We present here the results of observation of very high energy(VHE) gamma-ray emission from Crab Pulsar with the Beijing Atmospheric Cerenkov Telescopes, named ACT2 and ACT3, during the 1995－1996 season. The data are based on 168 h (ACT2) and 125 h (ACT3) of exposure over the period of observation in tracking mode. After converting the event time to the solar barycentre, the data have been searched for evidence of pulsed emission at 33 ms period of Crab Pulsar. We found no steady emission of VHE Gamma-ray with 33 ms period at the time scale of month or nights. But there are two evidences of sporadic emission over an hour duration with the same period as the one at radio wave band.

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