An accelerator mass spectrometry (AMS) system based on the HI-I3 tandem accelerator at the Institute of Atomic Energy (IAE) is described, and the first detection of ³⁶C1 with our AMS system is reported. The electrostatic deflector completely rejects isotopic background, ³⁵C1 and ³⁷C1. The ionization chamber distinguishs ³⁶C1 from isobaric background, ³⁶S. The measurement of ³⁶C1 with two samples is presented.

For a long pulse free-electron laser (FEL) in the low gain regime, an approximate expression is given to describe the optical field gain from the small signal to the weak saturation. The result is shown to agree with those from a 1-D computer simulation.

The nonlinear equation governing the nonpropagating solitary surface wave and its single solitary wave solution were derived by the method of multiple scales. The results obtained were compared with that in rectangular trough.

The finite width of the plateau in the Hall resistance is studied quantitatively. If we give a filling factor v, the ratio of the plateau width ΔB to the center of the plateau B_H square is constant for all other filling factors v' if v'=v+m with m any integer. The temperature dependence of the plateau width is also studied. Theoretical results are in good agreement with the data obtained from experiment.

The D_it (interface states density) in p-type MOS capacitors subjected to a preoxidation heat treatment was investigated by using DLTS (Deep Level Transient Spectroscopy) technique. It is found that the strong dependence of the D_it on POHT (Preoxidation Heat Treatment) and starting oxygen content of substrates is expected. The DLTS technique can detects the presence of bulk defect (E_t-E_v=0.29eV) at the interface presumably due to chlorine species.

The temperature dependences of the positron annihilation lifetime and the Doppler broadening shape parameters have been measured in high T_c superconductors YBa₂Cu₃O_7-x = between 77.2 and 300K. The measured parameters show an abrupt change across the range of superconducting transition temperature, indicating a change of the electronic structure. The structural instabilities have also been observed in three higher temperature ranges of115-135, 150-210 and 250-280K. This suggests that higher T_c superconductors might be found in these temperature ranges.

To explore high T_ce in Bi-Sr-Ca-Cu-O system, many different nominal compositions have been investigated. Zero resistance temperature T_ce as high as 105K and only one sharp 3uperconducting transition in a.c. susceptibility measurement has been observed in the nominal composition Bi₂Sr₂Ca₃Cu₄O_y by using the method of crystallization from glassy Bi-Sr-Ca-Cu-O at 875°C for above 50h.

The Czochralski growth of LaMgAl₁₁O₁₉:Nd³⁺ crystal is investigated. Its temperature fluorescence and absorption spectra are measured.

We have measured the time-resolved photoluminescence spectra of several In_xGa_1-xAs/GaAs single quantum well samples at 77K. The different temporal behaviors of the photoluminescence (PL) from the GaAs layer and the excitonic emission from the In_xGa_1-xAs well were obtained. The lifetime for the exciton in the In_xGa_1-xAs well were determined to be 110-170ps. The trapping efficiency of the well to the carriers was about 80%.

A novel μc-Si:F:H film growth technique has been developed using a windowless photo-enhanced chemical vapor deposition (photo-CVD) system. The films contain of two phases with the microcrystallites embedded in amorphous materials. The films contain the crystallites with volume of fraction of 0.17-0.23 and average grain size of 32-85nm. The conductivity up to 16(Ω.cm)^-1 and gauge factor (GF) of about 12 are obtained.

We develop a model to explain the high velocities of the ionized stellar winds around young stellar objects associated with magnetic fields. The plasma which is produced by the hot object nearby is turbulent and plays a significant role to accelerate particles. Then the high velocity winds encounter the ambient gas in a molecular cloud to form shock waves. The shocked gas emmision produces broad wings of CO line profiles.

A numerical calculation is made to find the arc images of background galaxies produced by cosmic strings(1oops) as lensing objects. The result shows that there should be several medium-sized arcs for each long arc discovered and further work should be done to distinguish cosmic string from galaxy cluster as deflector.