The reasonable wavefunctions of the vector mesons ρ, K* and D* are pro-posed and their properties are discussed. We calculated the decay processes D, B → Vlv and PV. Comparison of the results of our model with those of the Bauer-Stech- Wirbel (BSW) model and the experimental data are given. We also obtained the upper limit of V_ub which is smaller than that of BSW model.

We study the interacting neutron and proton boson model (IBM2) model without the assumption of the maxium F-spin truncation. Then we make a complete IBM2 calculation of the spectrum and E2 transitions to the ¹⁶⁸Er nucleus. Also from our simple condensate wavefunctions, we investigate a new mechanism of separate excitations of neutron and proton boson degrees.

The effects of masses of quarks and light gluions on the temperature of Quark-Gluon Plasma (QGP) is taken into account in Massachusetts Institute of Technology (MIT) bag model while freeze-out of quarks from QGP is discussed in the break-up model. It turns out that in the last stage of development of QGP, quark species will freeze-out in the heavier to lighter order, which may not be changed by unavoidable production of other particles (e. g., gluions).

Optical bistability hysteresis loop has been observed experimentally with a setup using prism excitation of surface wave in a doped polymer thin film. A simple model has been developed to analyze its operation. The observed bistability hysteresis loop can be explained in terms of surface plasmon excitation and laser induced refractive index variations.

Second harmonic generation conversion efficiency of 45% was obtained with a 12 mm long specially grown and cut MgO:LiNbO₃ crystal and fundamental peak power density of 140MW/cm².

Various progressive waves expressed by rational combination of Jacobian elliptic functions in general are found as solutions to the modified KdV equation. They reduce to cnoidal, dnoidal, snoidd, solitary waves or solitons and kinks in some special cases.

The crystllization process of metallic glass (Fe_l-xCr_x)₈₃B₁₇ (x=0.05, 0.10,0.15, 0.25) was studied by differential thermal analysis, X-ray diffraction technology. Experiment proved the atomic bond force as an important driving force in the phase transition. The crystallization peak shifts towards high temperature with the increase in the concentration of high melting point Cr atom. The main structural unit of as-quenched state of (Fe_l-xCr_x)₈₃B₁₇ metallic glass contains atomic cluster of local nine-atom structure.

We have measured directly the low field magnetization and its time decay of weak link superconductor in the sintered T1₂Ba₂Ca₂Cu₃O_10+x. The decay of magnetization with time at the field intensities of 5, 10, 15, 20 and 50 Oe was observed to follow the law of logarithm, M ∝ Int . The pinning potential derived from the slope of the magnetization decay is about 0.045~0.075eV.

In order to study how the Sn substitution for Tl changes the superconducting properties of the TlBaCaCuO compound, we have prepared samples with Sn in place of Tl by solid state reactions. Measurements of resistance and magnetic susceptibility show that partial substitution of Tl with Sn is helpful to form the superconducting 2223 phase (for T1:Ba:Ca:Cu). It has been found that samples mainly contain tetragonal phase 2223, but there also exist a few additional maxed phases like 1223, 1234 and nonsuperconducting phase BaSnO₃.

A relation of T_c ~σ.Jⁿ proposed after analysing the phase diagram and magnetic susceptibility experiments for La_2-xSr_xCuO₄ and Bi_2+xSr₂Ca_1-xCu₂O_y . This empirical rule agrees with the phase diagram for La_2-xSr_xCuO₄. We suggest that it should also hold for other superconducting cuprites.

Measurements of the Hall coefficient (R_H) were carried out for a polycrystalline YBa₂Cu₃O_7-y film, a well oriented YBa₂Cu₃O_7-y film and an oriented GdBa₂Cu₃O_7-y film. Sign change of RH was observed for the two YBa₂Cu₃O_7-y films near T_c, but not for the GdBa₂Cu₃O_7-y film which contains partly the component of (110) orientation. The R_H anisotropy model proposed previously turns out to be incorrect. Why the YBa₂Cu₃O_7-y films experience sign change of R_H while the GdBa₂Cu₃O_7-y film does not is tentatively investigated.

We have prepared single-phase superconducting T1₂CaBa₂Cu₂O₈ thin film by dc magnetron sputtering process and measured X-ray photoelectron spectra of the film at room and liquid nitrogen temperatures. From the relative intensities of the Ba3d, Tl4f. O1 s and Cu2p spectra taken at different take-off angles, we have concluded that there is an adventitious contamination (nonsupercon-ducting phase) surface layer. After excluding contributions from these spurious phases, we have tentatively assigned which core-level shifts should be caused by the superconducting phase transition.

The crystallographic and magnetic properties of Sm₂ Fe₁₇ N₂ and Y₂ Fe₁₇ N₂ have been investigated by using X-ray diffraction techniques and magnetic measurements. The effects of the interstitial nitrogen atoms on the Fe-Fe and R-Fe exchange interactions, iron 3d band structure and magnetocrystalline anisotropy induced by crystal field interactions in these nitride compounds are discussed.

The feasibility of pair produced positron annihilation technique, which provides the electron momentum information of materials by analyzing the spectrum from pair produced positron annihilation, is studied. In this technique the positrons produced by low energy r-ray in a sample are moderated and annihilated and the Doppler broadening annihilation spectrum is measured and analyzed.

Dynamic Monte Carlo simulation is used to explore the B isotope sputtering during 1 keV Kr ion irradiation. It is found that at both zero and high fluences the light isotope is preferentially ejected in the near-normal direction; meanwhile, there is a low fluence (1.4x10¹⁵ ions/cm²), at which the isotope fractionation is independent of the emission angle in the nearly whole angular range.