On the statistical independence of various column contributions to band broadening. Part 1: Second moment contributions from statistically independent,longitudinal diffusion in both phases

The total length-based second moment contribution from longitudinal sample diffusion in both phases on a column, σD , is derived by adding individual partial differential contributions to a partial differential equation accounting for the longitudinal diffusion processes only. Although each diffusion-dispersed sample part is equilibrated between two phases, the resulting σ,D (= 2D _mt _m + 2D _st _s) can be interpreted as the sum of two independent contributions in accordance with the variance addition rule. (D _m and D _s are the mean diffusion coefficients and t _mand t _s the mean residence times of the sample in the mobile and stationary phases, respectively.) The same σD expression is derived from the random walk model of Giddings by treating the diffusional process in each phase as statistically independent of the other processes. Under these conditions the broadening contribution from longitudinal diffusion in the mobile phase is shown to be independent of the velocity profile.     

A molecular theory of inhomogeneous broadening,including the correlation between different transitions,in liquids and glasses

Summary We present a molecular theory of the energy distributions for the internal quantum states of a solute in a liquid or glassy solvent. We show that the energy distributions for different states are correlated in a way that depends on the solute-solvent interactions. We show how the theory can be modified easily to describe the transition-energy distributions for different pairs of states, which are of course related to inhomogeneously broadened absorption spectra. We also show that the distributions for different transitions are correlated, and describe how this correlation is measured by nonresonant fluorescence- and phosphorescence-line-narrowing and hole-burning experiments. The theory provides a microscopic framework within which to interpret different phenomenological models. For the case of a Lennard-Jones solute in a Lennard-Jones liquid solvent, we compare our theory to Monte Carlo simulation.     

Vortex lattice mobility and effective pinning potentials in the peak effect region in YBCO crystals

The peak effect (PE) in the critical current density in both low and high temperature superconductors has been the subject of a large amount of experimental and theoretical work in the last few/several years. In the case of YBCO, crucial discussions describing a dynamic or a static picture are not settled. In that region of field and temperature the mobility of the vortex lattice (VL) is found to be dependent on the dynamical history. Recently we reported evidence that the VL reorganizes and accesses to robust VL configurations (VLCs) with different effective pinning potential wells arising in response to different system histories. One of the keys to understand the nature of the PE is to investigate the VL behavior in the vicinity of the various VLCs in the region of the PE. The stability of these VLCs was investigated and it was found that they have distinct characteristic relaxation times, which may be related to elastic or plastic creep processes. In this paper we review some of these results and propose a scenario to describe the PE in YBCO crystals.     

嵌入锂原子的zigzag型单壁碳纳米管的电子传导特性

运用基于第一性原理的密度泛函理论（DFT）的非平衡格林函数（NEGF）方法对Li原子嵌入后的zigzag型单壁碳纳米管(SWCNT)的电子输运性质进行了研究.在构建和优化了Li原子嵌入的zigzag型单壁碳纳米管的电子输运模型后,研究了该系统的电子传输概率、能态密度、电子透射谱,还研究了电子能量和偏置电压设置与变化对其电子输运特性的影响.结果显示zigzag型单壁碳纳米管嵌入Li原子后,电子输运特性发生了较大变化,具有电子输运拓宽效应和量子台阶复苏效应. 关键词： Li原子 碳纳米管 电子输运 拓宽效应     

Time domain measurement of dispersion in optical fibres

A time domain dispersion measurement apparatus was successfully built and tested at the Indian Institute of Technology, Madras. This instrument can measure directly the pulse broadening in a multimode optical fibre. The basic dispersion mechanisms in optical fibres and the design details of the system are discussed.     

基于二极管阵列检测器的色谱峰纯度的快速直观鉴定

基于二极管阵列检测器（DAD）得到的色谱-光谱图,通过去噪、归一化、计算欧氏距离,聚类分析等方法,建立了一种快速直观的评价色谱峰纯度的有效方法：可直观的判断色谱峰的纯度,并判断存在干扰峰的位置,为色谱工作者评价色谱峰,进行下一步工作提供了依据。     

高密度平面靶等离子体中激光驱动冲击波加速离子的能谱展宽

本文对超短超强激光脉冲辐照高密度等离子体产生的静电冲击波加速离子的能谱展宽机理进行了数值研究.着重讨论了三种冲击波加速离子的能谱展宽机理:能量沉积到离子中使得冲击波前沿不断减速,被加速离子与背景粒子的碰撞,以及高能离子到达靶背面时受到鞘层场进一步加速.还研究了驱动激光脉冲宽度对冲击波加速离子能谱宽度的影响. 关键词： 激光等离子体 冲击波加速 能谱展宽     

双路光谱展宽的钛宝石飞秒光学频率梳系统

对中国计量科学研究院研制的第一代基于钛宝石飞秒激光器的光学频率梳系统进行了改进和优化. 通过对激光器重复频率、光谱展宽以及拍频信号探测等方面的改进,有效地降低了光谱展宽的复杂性,提高了飞秒光学频率梳系统的稳定性和激光频率测量的便捷性. 采用该光学频率梳系统对碘稳频532 nm和碘稳频633 nm激光绝对频率进行了测量,测量结果在国际推荐值的不确定度范围之内. 关键词： 光学频率计量 飞秒光学频率梳 光谱展宽     

Measurements and calculations of H2-broadening and shift parameters of water vapour transitions of the ν1 + ν2 + ν3 band

The water vapour line broadening and shifting for 97 lines in the ν₁ + ν₂ + ν₃ band induced by hydrogen pressure are measured with Bruker IFS 125 HR FTIR spectrometer. The measurements were performed at room temperature, at the spectral resolution of 0.01 cm^?1 and in a wide pressure range of H₂. The calculations of the broadening γ and shift δ coefficients were performed in the semi-classical method framework with use of an effective vibrationally depended interaction potential. Two potential parameters were optimised to improve the quality of calculations. Good agreements with measured broadening coefficients were achieved. The comparison of calculated broadening coefficients γ with the previous measurements is discussed. The analytical expressions that reproduce these coefficients for rotational, ν₂, ν₁, and ν₃ vibrational bands are presented.