Millimetre wave oxygen attenuation measurements

A new measurement of the oxygen absorption line at 118,750 MHz under carefully controlled laboratory conditions shows the line broadening parameter at 300°K to be 2.11±0.05 MHz/torr.     

High-intensity femtosecond laser absorption by rare-gas clusters

The energy absorption efficiency of high-intensity (～10^{16}W/cm^2) femtosecond laser pulses in a dense jet of large rare-gas clusters has been measured. Experimental results show that the energy absorption efficiency is strongly dependent on the cluster size and can be higher than 90%. The measurement of the ion energy indicates that the average ion energies of argon and xenon can be as high as 90 and 100keV, respectively. The dependence of the average energy of the ions on the cluster size is also measured. At comparatively low gas backing pressure, the average ion energies of argon and xenon increase with increasing gas backing pressure. The average ion energy of argon becomes saturated gradually with further increase of the gas backing pressure. For xenon, the average ion energy drops a little after the gas backing pressure exceeds 9 bar (3.2×10^5 atoms/cluster). The result showing the existence of a maximum average ion energy has been interpreted within the framework of the microplasma sphere model.     

Millimetre wave spectrum of the weakly bound complex NH3-N2

The van der Waals complex NH₃-N₂ has been studied in the millimetre wave region, 76–106 GHz. Thirty-five lines were observed and assigned as pure rotational transitions, R(11) to R(15), belonging to six series involving all combinations of the parent molecule nuclear spin species, ortho/para-ammonia and ortho/para-nitrogen. Two of these series are continuations to higher J values of transitions observed previously in the microwave region, and the other four series were observed here for the first time. Predictions are given for a number of new NH₃-N₂ microwave transitions, and future observations of these should help to confirm the assignments given here. The time is ripe for theoretical investigations of NH₃-N₂ and the isoelectronic complex NH₃-CO.     

Small-angle neutron scattering by fractal clusters in aqueous dispersions of nanodiamonds

We considered how the choice of a model affects the treatment of data of small-angle neutron scattering by aqueous dispersions of detonation nanodiamonds. The scattering curves were analyzed using a general approach that combines the structure of nanodiamonds, the fractal organization of their clusters, and the interaction of clusters. The effect of the interaction between clusters on scattering was treated within the Guinier approximation.     

多轴差分吸收光谱技术反演气溶胶消光系数垂直廓线

研究了多轴差分吸收光谱技术(MAX-DOAS)的气溶胶消光系数垂直廓线反演算法. 该算法应用非线性最优估算法, 通过MAX-DOAS测量的氧的二聚体(O₄), 反演气溶胶消光系数垂直廓线和光学厚度(AOD). 首先研究了非线性最优估算法中权重函数、先验廓线协方差矩阵、测量不确定度协方差矩阵的计算方法, 针对中国气溶胶浓度较高且变化剧烈的特征, 设计了非线性迭代方案. 然后在低气溶胶、高气溶胶和抬高型气溶胶三种状态下, 通过计算机仿真模拟验证了MAX-DOAS气溶胶消光系数垂直分布反演算法, 讨论了误差来源. 之后在合肥地区开展了连续观测实验, 并将反演的AOD与CE318太阳光度计对比, 两者的相关性系数达到了0.94. AOD反演的相对误差约为20%. 又将反演的最低层(0–0.3 km)气溶胶消光系数与能见度仪对比, 两者的相关性系数为0.65. 近地面气溶胶消光系数反演的总相对误差约为10%. 模拟验证和对比实验均说明本文研究的气溶胶消光系数垂直廓线反演算法可以较好地获取对流层的气溶胶状态. 关键词： 多轴差分吸收光谱 气溶胶消光系数垂直廓线 气溶胶光学厚度 最优估算法     

大气气溶胶粒子光吸收系数的测量

采用核孔过滤膜累积气溶胶粒子的方法设计了气溶胶粒子光吸收系数的测量系统。该系统由双光路组成,可以减小光路损耗和电路噪声带来的各种测量误差。同时,具有体积小、光路易于调节、可进行实时测量、定标容易等特点。用200和400nm孔径的过滤膜,分别测量了实验室内大气气溶胶粒子对不同波长激光的吸收系数。随着累积时间的增加,系统的测量精度也不断的提高,在累积时间为900s时,系统测量误差为9.849×10-6/m。     

大气气溶胶粒子光吸收系数的测量

 采用核孔过滤膜累积气溶胶粒子的方法设计了气溶胶粒子光吸收系数的测量系统。该系统由双光路组成,可以减小光路损耗和电路噪声带来的各种测量误差。同时，具有体积小、光路易于调节、可进行实时测量、定标容易等特点。用200和400nm孔径的过滤膜，分别测量了实验室内大气气溶胶粒子对不同波长激光的吸收系数。随着累积时间的增加，系统的测量精度也不断的提高，在累积时间为900s时，系统测量误差为9.849×10^-6/m。     

气溶胶吸收的光热干涉相位载波算法

解调算法是干涉测量的关键技术之一, 通过初步搭建的光纤式光热干涉装置对相位载波解调算法进行了仿真与实验研究。介绍了装置采用的单光路垂直反射式干涉结构, 阐述了相位载波调制解调的机理, 并利用光纤式光热干涉装置, 通过向压电陶瓷施加不同电压来模拟实际大气气溶胶吸收情况完成对相位载波算法解调能力的检验, 并与不同质量浓度NO2标准气体下的实测相位信号、仿真解调相位信号和通过干涉条纹计算法获得的结果进行对比验证, 证明相位载波解调算法可以满足光纤式光热干涉气溶胶吸收测量装置的信号解调工作的要求。     

气溶胶吸收的光热干涉相位载波算法

解调算法是干涉测量的关键技术之一, 通过初步搭建的光纤式光热干涉装置对相位载波解调算法进行了仿真与实验研究。介绍了装置采用的单光路垂直反射式干涉结构, 阐述了相位载波调制解调的机理, 并利用光纤式光热干涉装置, 通过向压电陶瓷施加不同电压来模拟实际大气气溶胶吸收情况完成对相位载波算法解调能力的检验, 并与不同质量浓度NO2标准气体下的实测相位信号、仿真解调相位信号和通过干涉条纹计算法获得的结果进行对比验证, 证明相位载波解调算法可以满足光纤式光热干涉气溶胶吸收测量装置的信号解调工作的要求。     

Anderson localization and wave absorption

Experimental signatures of classical wave localization in the absence and in the presence of attenuation are analyzed. The different regimes of the attenuation, reflection, and transmission coefficients for the diffusive and localized regimes are discussed. Apparent contradictory results presented previously by John and Anderson on the renormalization of absorption by localization are reconciled and shown to apply to different situations.     

Probing the chemical reactivity of free titanium clusters by x-ray absorption spectroscopy

Synchrotron radiation-based experimental techniques are largely employed for the characterization of the reactivity of finite size systems; in particular, x-ray absorption spectroscopy (XAS) is a suitable tool to shed light on the local electronic structure and chemical status of atoms in nano-objects, as it is very sensitive to the local bonding environment of the probed site. In supported clusters intrinsic properties and reactivity are largely distorted and obscured by the changes imposed by the growth procedure and by the influence of the substrate, so the attainability of experiments on free clusters reacting with species in the gas phase is a primary goal in the development of cluster science. In this paper we report a proof of principle of the applicability of gas phase XAS technique to titanium and titanium oxide, hydride and hydrate systems. Experiments are performed by coupling a pulsed microplasma cluster source (PMCS) with a third generation synchrotron light source, and measuring the intensity of the electron yield coming from the interaction of VUV photons with the clusters seeded in a supersonic beam.     

Millimeter and submillimeter wave absorption by atmospheric pollutants and constituents

Calculated absorption coefficients and rotational transition frequencies ara given for a number of polar molecules of interest to pollution and energy research. The results, which are presented in graphical form for microwave frequencies up to 1400 GHz, illustrate the increased absorption line intensities occurring in the submillimeter region. For most species, these absorption coefficients attain their maximum values in this region. Included in the calculations are SO₂, H₂CO, O₃, H₂O, H₂S, OCS, CO, NO, OH, SO, NH₃, and CS. A discussion of the techniques currently available for detection in the submillimeter region of these species is also given.     

Total absorption of an electromagnetic wave by an overdense plasma

We show both theoretically and experimentally that an electromagnetic wave can be totally absorbed by an overdense plasma when a subwavelength diffraction grating is placed in front of the plasma surface. The absorption is due to dissipation of surface plasma waves (plasmons polaritons) that have been resonantly excited by the evanescent component of the diffracted electromagnetic wave. The developed theoretical model allows one to determine the conditions for the total absorption.