基于量子点接触的开放双量子点系统电子转移特性

基于量子点接触探测器(QPC)理论上研究了双量子点(DQD)系统在耗散环境和纯退相环境影响下的电子转移特性.结果表明,耗散环境中探测器导致的退相干会增大平均电流和Fano factor随时间演化的值,并观察到量子芝诺效应的存在.在对称的DQD情况下,弛豫减小了平均电流随时间演化的震荡振幅.在非对称的DQD情况下,弛豫降低了Fano factor随时间演化的峰值.纯退相环境中测量会阻碍共隧穿过程中不同电流通道之间的转换,导致Fano factor的极高值.在对称的DQD情况下,增大纯退相速率会提高Fano factor.在非对称的DQD情况下,动力学随时间的演化对纯退相环境不敏感.另外,还发现探测器内n个电子的转移几率只受QPC与DQD耦合的影响.我们的结论可以为实验工作者研究电子输运特性提供理论参考.     

长清地区春季大气中颗粒物的SEM观察与分析

利用扫描电镜观察分析了长清地区春季大气中颗粒物显微形态及粒径分布状况,采用统计回归分析方法绘制了连续30 d的大气颗粒物粒径与数量分布状况关系曲线及相应的柱状图.试验结果表明:大气颗粒物主要集中在0~1.0μm和1.0~2.5μm的粒径范围内,显微形态有不规则的颗粒状、块状、圆球状、棒状和片状等.另外,还观察到了杆菌和花粉的显微形态.试验结果对于研究大气中PM2.5、PM10及大气污染状况具有一定的参考价值.     

Fractal dynamics in the ionization of helium Rydberg atoms

We study the ionization of helium Rydberg atoms in an electric field above the classical ionization threshold within the semiclassical theory.By introducing a fractal approach to describe the chaotic dynamical behavior of the ionization,we identify the fractal self-similarity structure of the escape time versus the distribution of the initial launch angles of electrons,and find that the self-similarity region shifts toward larger initial launch angles with a decrease in the scaled energy.We connect the fractal structure of the escape time plot to the escape dynamics of ionized electrons.Of particular note is that the fractal dimensions are sensitively controlled by the scaled energy and magnetic field,and exhibit excellent agreement with the chaotic extent of the ionization systems for both helium and hydrogen Rydberg atoms.It is shown that,besides the electric and magnetic fields,core scattering is a primary factor in the fractal dynamics.     

Analysis of the fractal intrinsic quality in the ionization of Rydberg helium and lithium atoms

We study the fractal rhythm in the ionization of Rydberg helium and lithium atoms in an electric field by using the semiclassical method. The fractal structures present a nested relationship layer by layer in the initial launch angles of the ionized electrons versus the escape time, which is defined as the rhythm attractor, and exhibit similar rhythm endings. The gradually enhanced chaotic regions of the escape time plots tend to broaden as the scaled energy increases. In addition,the fractal rhythm changes synchronously with the oscillations of the kinetic energy spectrum. We note that the intrinsic quality of the fractal rhythm is closely related to the kinetic energy distribution, that is, the inherent dynamic properties of the Hamiltonian equations have an impact on the fractal regularities. In addition, different ionizing closed trajectories exhibit iterate properties and the inherent beauty of symmetry. Our results and analysis can not only reveal new laws in the ionization of Rydberg atoms, but also promote the establishment of the dynamic mechanism of fractals.