光磁共振实验反常共振信号的判断与原因分析

对光磁共振实验中各反常共振信号对应的射频信号进行了研究,提出了反常共振信号的判断方法.利用傅立叶级数展开,对反常射频信号各谐波分量的强度进行了定量分析.结果表明,反常共振信号是由射频信号中的谐波所引起,而非多量子跃迁的结果.     

Thermal annealing behaviour of Al/Ni/Au multilayer on n-GaN Schottky contacts

Recently GaN-based high electron mobility transistors (HEMTs) have revealed the superior properties of a high breakdown field and high electron saturation velocity. Reduction of the gate leakage current is one of the key issues to be solved for their further improvement. This paper reports that an Al layer as thin as 3 nm was inserted between the conventional Ni/Au Schottky contact and n-GaN epilayers, and the Schottky behaviour of Al/Ni/Au contact was investigated under various annealing conditions by current--voltage (I--V) measurements. A non-linear fitting method was used to extract the contact parameters from the I--V characteristic curves. Experimental results indicate that reduction of the gate leakage current by as much as four orders of magnitude was successfully recorded by thermal annealing. And high quality Schottky contact with a barrier height of 0.875 eV and the lowest reverse-bias leakage current, respectively, can be obtained under 12 min annealing at 450°C in N₂ ambience.     

反常扩散:定向通过一个势能鞍点

考虑一个处于非Ohmic环境下的系统定向通过一个倒谐振子势鞍点的输运过程,给出了通过几率的解析式。结果表明在欠扩散情况下,时间有关的通过几率出现一个很强的超前峰和回流,这可能有助于理解重核熔合系统的激发函数随质心能量的慢增长机制。Directional transport of a particle in a non-Ohmic environment passing over the saddle point of a potential is considered and the analytical expression of the passing probability is obtained. Our results has shown that both overshooting and backflow are observed in the case of subdiffusion. This is a possible for understanding slow increasing of the fusion probability with the center-of-mass energy.     

Anomalous spectral behaviour of diffracted chirped Gaussian pulses in the near field

By using the Fourier transform method, analytical expressions for the axial power spectrum and near-field intensity in the spacetime domain of chirped Gaussian pulses diffracted at an aperture are derived, which permit us to study changes in spectral and temporal profiles of the chirped Gaussian pulses both analytically and numerically. Detailed numerical results and physical analysis show that spectral anomalies take place in the neighbourhood of certain critical distances, and the shifting of maximum and splitting of temporal intensity profiles appear. In particular, for ultrashort chirped pulses, there exists also spectral switch. Besides the truncation parameter, the chirp parameter and pulse duration affect the behaviour of spectral switches.     

强磁场与涡旋场中的夸克胶子物质

相对论重离子碰撞可以产生高温的夸克胶子物质，同时也产生极强的电磁场和流体涡旋。在强电磁场和涡旋场中的夸克胶子物质呈现出新奇的宏观量子现象，比如手征磁效应、手征涡效应、手征分离效应、手征电分离效应、自旋极化现象等。它们一方面给我们提供了可以探测高温下量子色动力学的非平庸规范场拓扑结构、强相互作用的宇称破坏、夸克胶子物质中的自旋动力学等的实验手段，另一方面也与物理学其他分支，比如粒子物理、凝聚态物理、天体物理、冷原子物理等发生紧密联系，形成新的交叉研究领域。本文旨在对这些宏观量子现象的产生机制以及它们在相对论重离子碰撞中的探测等做一回顾和展望。特别地，我们揭示出重离子碰撞的磁场强度可以达到$10^{18}\sim 10^{20}$ G，流体涡旋可以达到$10^{22}$ s–1；这是我们已知当前宇宙中最强的磁场和流体涡旋。我们定量地对同量素碰撞实验做了分析，发现即便背景比例达到93%以上，当前的同量素碰撞实验仍然可在大约$3\sigma$的显著性水平上判断是否有手征磁效应的发生。我们系统地给出了满足因果律的自旋流体力学方程，并推导了其中的集体激发模式，这将有助于理解超子自旋极化中出现的符号问题。     

有限反常核

从一个相对论性核模型解得了有限反常核,并找到了两个临界质量数A₁=85和A₂=165,只当质量数A≥A₁时才存在束缚的反常核,当A≥A₂时反常核的第核子结合能大于正常核.当A>3310时反常核由于库伦能而变得非束缚.     

剖面不变性、反常电子热导及托卡马克装置约束性能分析

本文根据电子温度剖面不变性这一基本实验现象,通过分布量决定的广义对流能流的引入及其与局部量决定的局部反常电子热导关系的分析,在不涉及等离子体整体能量输运物理机制的情况下,给出了托卡马克装置约束性能更可信的描述方式。     

用低杂波驱动电流的等离子体电导率

本文用Liu的低杂波驱动电流模型,导出了弱场近似下低杂波驱动电流的等离子体电导率。结果表明,电导率对磁场B_0,电子密度n_0,以及电子温度T_e非常敏感。而这些参量决定着共振电子的数目和速度。     

Transition State Theory Rate in Nonlinear Environment： the Under-damping Case

We investigate the escape behavior of systems governed by the one-dimensional nonlinear Kramers＇ equation δW/δt = -vδW/δx ＋ （f＇（x）/m）（δW/δv） ＋ γδ（vW）/δv ＋ （γκBT/m）（δ2W^μ/δv^2）, where f（x） is a metastable potential and μ an anomalous exponent. We obtain an expression for the transition state theory escape rate, whose predictions are in good agreement with numerical simulations. The results exhibit the anomalies due to the nonlinearity in W that the TST rate grows with T and drops as μbecomes large at a fixed T. Indeed, particles in the subdiffusive media （μ 〉 1） can escape over the barrier only when T is above a critical value, while there does not exist this confinement in the superdiffusive media （μ 〈 1）.     

漂移波不稳定性引起的反常电子热导的估计

本文从漂移波引起的湍性磁场出发,考虑了漂移波不稳定性引起的反常电子热导,所得电子热导的数值与实验结果基本符合,并利用所得的反常电子热导,在欧姆加热条件下推导了电子能量约束时间。