In this paper the coherent and the squeezed state of the bose field is written as a universal form by means of a projector which transforms the old vacuum state to the new vacuum state. The transformed vacuum state is the coherent state or the squeed state. Our result is equivalent to the original definations.

By considering a beam of two-level atoms traversing a sequence of propagating light wave tuned to atomic transition in optical ring cavities, a large momentum transfer is obtained. This is a new scheme for realization of atomic splitter and it can be used to construct atom interferometer.

The quantum phase of a moving dipole as it encircles an infinite line of magnetic charge, recently discovered by Wilkens (Phys. Rev. Lett. 72 (1994) 5), is derived as a special case of Berry’s phase.

The connection is found between the star-triangle relation and the star-square relation in the Baxter-Bazhanov model which is an Interaltion-Round-a-Cube model. This gives a proof of the guess suggested by Bazhanov and Baxter.

In terms of the Dirac's finite contact transformation, we derive the principle on the choice of gauge conditions in the general singular Lagrangian system. It is applied successfully to Cawley's first counter-example of Dirac's conjecture. The number of gauge conditions or gauge freedoms is given and it is shown to be different from the accustomed conclusion which is always equal to the number of all the first-class constraints .

By taking account of the finite-size effect rationally in the framework of the Hartree-Fock theory, the compression modulus K_A at zero temperature of finite nuclear matter is evaluated with the Skyrme force SKM^*. Energies of the isoscalar giant monopole resonance of nuclei calculated are found to be in agreement with the experimental and empirical values. The influence of neutron-proton asymmetry, finite size and Coulomb force effects on K_A is also investigated.

In Otsuka's view of nuclear rotations neutrons and protons are not rotating around a common axis, but rather around separate axis. In this letter, we pointed out that this invalidates the geometrical interpretation of F-spin structure of the neutron-proton interacting boson model, where the angle between the axis of symmetries of neutron ellipsoid and proton ellipsoid is used to determine whether a state is F-spin symmetric or mixed symmetric.

The effect of excessive mesons on the meson-nucleon interaction in nuclei is studied. It is shown that even if nonlinear meson interactions are considered, excessive mesons exist in the nuclear ground state (GS) and the GS expectation value of the meson-nucleon interaction Hamiltonian is exactly equal to zero if there are no excessive mesons.

By using the parton momentum distribution of the bound nucleon given by the improved parton evolution model, we calculate the nuclear Drell-Yan ratios of nuclei: C, Ca, Fe and W to D. The calculated results are in qualitative agreement with the experimental data from the E772 collaboration.

We here present a relativistic multichannel theory which can be regarded as an extension of traditional configuration interaction theories by including continuum configuration interactions. Our relativistic multichannel theory aims directly to calculate the compact set of physical parameters ( μ_α,U_iα ) in multichannel quantum defect theory. Taking Ar atom as an example, we compare our calculated orbital energies with traditional configuration interaction calculations as well as experimental measurements.

The absorption spectrum of a new sort of crystal Nd:S-VAP was measured, which showed that Nd:S-VAP can be appropriately pumped at 583.0 and 809.0nm. By using tunable dye-laser (570.0-600.0nm) as pumping light, the performance of low threshold and high efficiency Nd:S-VAP laser has been realized. The characteristics of the output laser, such as 1.5nm linewidth, 5 ns pulse width, almost total polarity, up to 50% conversion efficiency, down to 2mJ threshold energy and so on, were presented. Meanwhile, the prospect of Nd:S-VAP crystal for low threshold, high efficiency miniature laser was discussed.

We have observed the two-wave mixing of the photorefractive GaAs/AIGaAs semiinsulating multiple quantum wells fabricated by film lift-off approach and proton implanting technique. Under the non-optimized condition, we have obtained the two-wave mixing gain larger than 180cm^-1 at wavelength near 784nm for a field of 10kV/cm. Energy transfer is also observed when the applied field is perpendicular to the grating vector.

The preliminary experimental results of ac plasma discharges in the CT-6B tokamak have been achieved by an active plasma current feedback system and the keys to a smooth transition through current zero and some phenomena related to the current reversal phase are also presented.

In this paper, the lattice vibrations of barium metaborate (β-BaB₂O₄) crystal are analysed with the aid of space group theory. The β-BaB₂O₄ crystal belongs to space group C⁶_3v(R3C). The vibration modes are classified by the method of the factor group of the space group. The results of infrared and Raman spectra have been given .

We study how thermodynamic properties of the four-spin interaction Ising model on a family of Sierpinski carpets fractals cross over to that of the Ising model on square lattice with four-spin interaction in half of the square faces. The exact free energy f_s for the square model and f_f for the fractals are obtained in a closed form and found to be analytic in temperature. The free energy varies smoothly with the geometrical parameter b (which labels each member of the fractal family) and for large b the difference between f_s and f_f is asymptotically proportional to l/b².

The thermodynamical properties of silver are calculated by using a recent model of many-body potential from lattice inversion method. The predictions of the phonon dispersion relation, the Grüneisen constant and the linear thermal expansion coefficient are all in coincidence with experiments. Of more importance, the present approach represents an efficient way of building potential functions capable of depicting the thermodynamics of metals for the Finnis-Sinclair model.

The Czochralski growth of large high-quality crystal Nd:La₂Be₂O₅(Nd:BEL) has been investigated. The Nd absorption in lanthanum beryllate (BEL) is broader and more intense than in YAG in the spectra region of 805 to 820nm. In particular, Nd:BEL has greater energy storage capacity of ability of higher levels of Nd-doping. BEL might outperform YAG as a host for diode-pumped Nd laser.

By placing a hole blocking layer between the polymer and the metallic electrode, we have achieved improved efficiencies for blue electroluminescent devices fabricated with poly (N-vinylcarbazole) doped with 1, 1, 4, 4, -tetraphenyl-1, 3-butadiene as the emitter layer and with aluminum and indium/tin-oxide as the electron and hole injecting electrodes. This bilayer device yields bright blue emission having intensity of 300cd/m², in same case the devices without hole blocking layer have luminance of only 44 cd/m².