激光雷达湍流大气探测

基于湍流对激光束的扩散和漂移效应,提出了一种采用激光雷达观测湍流强度的方法。湍流对光束产生扩散和飘移作用,使激光光束偏离激光雷达接收视场,造成后向散射光能量损失。对比常规散射回波信号与畸变回波信号的差别可以测量湍流强度。实验表明该方法与其他方法的测量结果具有一致性,证明了该方法的有效性。     

傅里叶变换红外光谱对水溶性气溶胶复折射率的测量分析方法研究

当前大气气溶胶的成分比较复杂,其水溶性离子成分影响着大气质量,并且对人类健康不利。因此,对水溶性离子成分进行快速可靠的检测是环境科学领域中的一项重要研究工作。以SO24-为例,研究采用傅里叶变换红外光谱(FTIR)技术,对水溶性气溶胶离子的消光系数进行测量,并通过理论分析计算得到其复折射率N的过程。通过测量大气气溶胶水溶性SO24-离子的质量消光截面k和消光系数α,再根据消光系数α来计算复折射率N的虚部ni,使用KK(Kramers-Kronig)关系,来计算复折射率N的实部nr,并对实验结果进行了分析和讨论。     

液体折射率的一种新型测量方法

利用液体薄膜的遮光效应原理,建立了一种新的测量液体折射率的方法和装置。选择了3种常见液体:蒸馏水 、无水乙醇 和1,2-丙二醇。利用新建的装置对其折射率进行了测量。实际测量过程中,对实验形成的图样进行了2种测量分析:一种是利用读数显微镜直接测量分析实验结果;一种是利用CCD拍摄记录实验结果,并利用计算机对拍摄结果进行了智能化处理分析。分析了实验误差,实现了实时、全自动化测量。测量结果均与理论值吻合。该方法操作简便、设备简单、重复性好、准确度高。     

基于平行平板的折射率高精度非接触测量

常用的测量折射率的方法如偏向角法、自准直法、临界角法、 V棱镜法等,这些方法通常需特制三棱镜与待测件。待测样品不一致且过程复杂,测试定标周期长,难于自动化。为了保证待测材料的完整及实现自动化测量,进行了基于平行平板的折射率非接触测量的尝试。运用该方法进行折射率的测量,不需特制三棱镜并且待测件与待测样品一致。分析表明,通过选择合适的测量角度,该方法旋转角度精度为a=0.003（即10）,导轨精度为L=0.000 8 mm,平行平板厚度测量精度为d=0.001 mm。     

外混合气溶胶粒子光散射的等效性

以两种典型的气溶胶粒子组成的单分散和多分散处理混合气溶胶粒子系统的光散射的各效率因子，各散射截面和散射相函数分析了以等效折射率描述由具有不同折射率的各种粒子组成的混合气溶胶粒子系统的适用性，结果表明，对单分散系统，本不同的混合比下对于许多尺度参数吸收效率因子和散射相函数的等效性很差，对多分散系统，在不同的混合比下等效性较稳定但各散射光学量的余差很大，因而对多分散系外混合气溶胶粒子系统如使用等效折射     

长焦距光学系统杂光系数测试仪

报告了一种新的长焦距光学系统杂光系数测量装置,该装置除具有避免了制作大直径积分球的优点外,还能精确测量轴外杂光系数,分析各部分杂光源对杂光系数的影响.     

渐变折射率光纤标量近似的微扰修正方法

在弱波导近似下,计及了折射率梯度的影响,把▽ε看作微扰项,应用微扰理论,给出了修正到任一级近似的标量场方程,建立了一级修正解的一般表达式,并给出了相关参量的确定方法。最后,以抛物线折射率剖面单模光纤为例,给出了简要分析结果。     

EELS studies of surface phonons on Ag(111)

High-resolution electron energy loss spectroscopy is used to study surface phonons in the direction of qG on Ag(111). The gap mode (S₂) at in the surface Brillouin zone is measured for the first time. We have also measured the Rayleigh mode and the resonance mode up to the zone boundary. The results are complementary to the earlier He atom scattering measurements and are in good agreement with the first-principles calculations performed recently.     

Adatom concentration on GaAs(001) during MBE annealing

We study the concentration of adatoms on GaAs(001) during annealing under MBE conditions. By rapidly cooling the sample from typical growth temperatures and typical As overpressures, the thermal concentration of adatoms can be frozen into small islands on the terraces. The area of the resulting islands is measured with STM far from terrace steps, giving an estimate of the concentration of adatoms during equilibrium. We find that a surprisingly large concentration of adatoms is present for typical growth temperatures, e.g. 0.18 monolayer at 600°C. Possible consequences for current growth models are discussed.     

The adsorption and decomposition of NO on Pd(110)

The sticking probability of nitric oxide (NO) on Pd(110) and the relative selectivity of the surface to nitrogen (N₂) and nitrous oxide (N₂O) production has been measured as a function of coverage and as a function of surface and gas temperatures using a molecular beam. It is found that, at low temperatures (<440 K), molecular adsorption occurs with an initial sticking probability of 0.40 ± 0.02, rising quickly to a maximum of about 0.48 ± 0.02 as coverage increases before falling towards saturation. Following adsorption at 170 K four distinct adsorption sites can be identified by subsequent TPD. Hence, if beaming occurs at a temperature above the TPD peak due to a given site, then that site cannot be populated and the saturation coverage is found to be reduced. At higher temperatures (440–650 K) the sticking probability is seen to decrease continuously as a function of coverage. At a given NO uptake, the sticking probability falls with temperature indicating that the rate of NO desorption is significant in this temperature range. In addition, dissociation occurs leading to the desorption of nitrogen and nitrous oxide leaving only oxygen adatoms on the surface. The oxygen adatoms poison further reaction but can be cleaned off, even at the lowest temperature at which dissociation occurs, by hydrogen or carbon monoxide. At the low temperature end of this range more nitrous oxide is produced than nitrogen but this ratio falls with temperature until, above 600 K, there is 100% selectivity to the production of nitrogen which we propose is due to the low lifetime of molecular NO on the surface. However, at such high temperatures, reaction only occurs on a few sites probably located at the few step edges present on the crystal.