索末菲参量对三重微分截面的影响

在前期工作的基础上，对非对称几何条件下波函数中的索末菲参量作了进一步的完善。研究了索末菲参量对三重微分截面（ＴＤＣＳ）产生的影响。用新的索末菲参量计算了低能电子入射离化氢原子的ＴＤＣＳ。所得结果与前期工作及ＣＣＣ（ｃｏｎｖｅｒｇｅｎｔｃｌｏｓｅ－ｃｏｕｐｌｉｎｇ）理论结果进行比较发现：所得结果明显地改善了理论曲线与实验数据的符合程度     

Theoretical calculation of the triple differential cross sections of the 2p orbital of argon in a coplanar highly asymmetric（e,2e） reaction

The triple differential cross sections of the 2p electron of argon in a coplanar highly asymmetric geometry have been calculated with the modified distorted wave Born approximation (DWBA) and the target Hartree－Fock approximation methods. The damping polarization of the semi-classical short-range potentials and the M_ee factor are included in the distorting potentials of the modified DWBA. Theoretical results are compared with a recent experiment. The dynamic mechanism of inner shell ionization in a coplanar highly asymmetric geometry (e, 2e) reaction are also discussed.     

On the characterization of the elastic properties of asymmetric single-walled carbon nanotubes

In order to characterize asymmetric single-walled carbon nanotubes, an algorithm has been developed based on numerical simulation to relate the physical geometry to the elastic properties of asymmetric single-walled carbon nanotubes (SWCNTs). A large number of finite element results for the stiffness of asymmetric SWCNTs has been used to develop a best surface fitting function to define the relationship between the geometry of SWCNTs and their stiffness. However, since the stiffness of asymmetric nanotubes depends upon the configuration parameters, n and m, it was impossible to define any diameter dependency. Based on the maximum reaction force concept and in order to account for the hidden mechanical behavior of asymmetric SWCNTs, the chiral factor (CF) has been employed in this study. The proposed CF converts any asymmetric geometry (n and m) into a value between 0 and 1. A group of the SWCNTs with the same applied boundary condition (n+m=30) and different range of the CF was also used for studying of the shear contribution. The chiral factor dependency, which is developed in this study, is applicable for characterising and selecting asymmetric SWCNTs in the design of advanced nanomaterials. Furthermore, the equation which is calculated in this study can be useful for finding the best criteria for selecting asymmetric SWCNTs.     

Nonideal effects in quantum field-effect directional coupler

The nonideal effects in a quantum field-effect directional coupler where two quantum wires are coupled through a finite potential barrier are studied by adopting the lattice Green function method. The results show that the electron energy distribution, asymmetric geometry and finite temperature all have obvious influence on the electron transfer of the coupler. Only for the electrons with energies in a certain region, can the complete periodic transfer between two quantum wires take place. The conductance of these electrons as a function of the barrier length and potential height exhibits a fine periodic or quasi-periodic pattern. For the electrons with energies beyond the region, however, the complete periodic transfer does not hold any more since many irregular oscillations are superimposed on the conductance profile. In addition, the finite temperature and asymmetric geometry both can reduce the electron transfer efficiency.     

Ionization of metastable H(2S) atom by electron and positron impact

Summary Triple differential cross-section (TDCS) of hydrogen atom in its metastable (2S) state is studied theoretically by electron and positron impact for coplanar and asymmetric geometry. The final-state wave function in the present model satisfies the asymptotic boundary condition for asymmetric geometry (i.e. fork ₁≫k ₂). In the absence of experiment, present results are compared with other existing theoretical results. Apart from the double-peaked structure of the TDCS as in ground-state ionization, some interesting secondary structures are found, in conformity with other theories for ionization from 2S state.     

DYNAMIC SCREENING OF THE THREE-BODY COULOMB INTERACTIONS

The BBK approach is modified by the introduction of effective Sommerf eld parameters for both symmetric and asymmetric geometries, according to the fact that the strength of any particular two body Coulomb interaction is affected by the presence of the third particle. The triple differential cross sections for electron impact ionization of atomic helium at incident energies of 40 and 50 eV in asymmetric geometry are calculated. Results of this approach are found to be in good agreement with the absolute measurements and the only existing theoretical results of the convergent close-coupling method.     

Experimental investigation of the breakdown of the Onsager-Casimir relations

We use magnetoconductance fluctuation measurements of phase-coherent semiconductor billiards to quantify the contributions to the nonlinear electric conductance that are asymmetric under reversal of magnetic field. We find that the average asymmetric contribution is linear in magnetic field (for magnetic flux much larger than 1 flux quantum) and that its magnitude depends on billiard geometry. In addition, we find an unexpected asymmetry in the power spectrum of the magnetoconductance with respect to reversal of magnetic field and bias voltage.     

（e,2e）反应中末态波函数的动量相关

在Ｂｅｒａｋｄａｒ工作的基础上,从动量相关的角度入手,导出了在任意几何条件下的索末菲参量。并由此计算了入射能为５０ｅＶ和１５０ｅＶ时,电子入射离化Ｈｅ原子的三重微分截面（ＴＤＣＳ）。将计算结果与相应的实验和ＣＣＣ理论结果进行 现：尽管计算与实验略有偏差,但总体上符合得较好。     

The effect of dynamical screening on helium （e, 2e） fully differential cross-sections

This paper presents the fully differential cross sections (FDCS) for 102eV electron impact single ionization of helium for both the coplanar and perpendicular plane asymmetric geometries within the framework of dynamically screened three-Coulomb-wave theory. Comparisons are made with the experimental data and those of the three-Coulomb wave function model and second-order distorted-wave Born method. The angular distribution and relative heights of the present FDCS is found to be in very good agreement with the experimental data in the perpendicular plane geometry. It is shown that dynamical screening effects are significant in this geometry. Three-body coupling is expected to be weak in the coplanar geometry, although the precise absolute value of the cross section is still sensitive to the interaction details.