晶体面形畸变对三倍频转换效率的影响

在惯性约束聚变(ICF)领域,为了满足物理实验需求,需要采用短波长的紫外激光打靶。目前,国内外高功率固体激光装置普遍采用谐波转换的方式来获得三倍频紫外激光。高效的频率转换必须满足相位匹配条件,而晶体的反射面形畸变过大对准直精度和倍频效率均匀性都会产生不利影响。通过实验验证了晶体准直光斑的质量退化主要来源于晶体因夹持和重力导致的反射面形畸变,证明了改进晶体的夹持方式可以有效改善晶体面形,提高准直精度和准直光斑质量,并显著提升三倍频转换效率。     

红外光谱阵列相关系数法在丹参鉴别中的应用

采用红外光谱阵列相关系数比对法对中国传统中药——丹参的产地与生长环境进行了鉴别研究。结果表明, 对特定谱段范围内设置较高相关系数阈值进行比对能快速鉴别丹参产地;对R5—R7谱段范围内设置较低相关系数阈值的设置能对丹参进行生长环境分类识别。该方法对丹参的聚类识别具有快速、简便、准确的特点。     

Time-Resolved Spectroscopy and Electronic Structure of Mono-and Dinuclear Pyridyl-Triazole/DPEPhos-Based Cu(I) Complexes

Chemical and spectroscopic characterization of the mononuclear photosensitizers [(DPEPhos)Cu(I)(MPyrT)]^0/+ ( CuL , CuLH ) and their dinuclear analogues ( Cu₂L’ , Cu₂L'H₂ ), backed by (TD)DFT and high-level GW-Bethe-Salpeter equation calculations, exemplifies the complex influence of charge, nuclearity and structural flexibility on UV-induced photophysical pathways. Ultrafast transient absorption and step-scan FTIR spectroscopy reveal flattening distortion in the triplet state of CuLH as controlled by charge, which also appears to have a large impact on the symmetry of the long-lived triplet states in Cu₂L’ and Cu₂L'H₂ . Time-resolved luminescence spectroscopy (solid state), supported by transient photodissociation spectroscopy (gas phase), confirm a lifetime of some tens of μs for the respective triplet states, as well as the energetics of thermally activated delayed luminescence, both being essential parameters for application of these materials based on earth-abundant copper in photocatalysis and luminescent devices.     

Reducing field distortion for galvanometer scanning system using a vision system

Laser galvanometer scanning systems are well-established devices for material processing, medical imaging and laser projection. Besides all the advantages of these devices like high resolution, repeatability and processing velocity, they are always affected by field distortions. Different pre-compensating techniques using iterative marking and measuring methods are applied in order to reduce such field distortions and increase in some extends the accuracy of the scanning systems. High-tech devices, temperature control systems and self-adjusting galvanometers are some expensive possibilities for reducing these deviations. This contribution presents a method for reducing field distortions using a coaxially coupled vision device and a self-designed calibration plate; this avoids, among others, the necessity of repetitive marking and measuring phases.     

Revealing distortion of carbon nanotube walls via angle-resolved X-ray spectroscopy

Arrays of aligned single-walled carbon nanotubes (SWCNTs) produced by supergrowth method were studied by scanning electron microscopy (SEM) and angle-resolved near-edge X-ray absorption fine structure spectroscopy, which defined that nanotube disorder is 10–13° and 23–27°, respectively. The latter value was confirmed by X-ray fluorescent spectroscopy. The difference in the obtained angular deviations was attributed to distortion of the SWCNT walls, because the X-ray spectroscopy methods are sensitive to a local environment of probing atoms, while the SEM examines the nanotubes at a substantially larger length scale. Significant distortion (20–24°) of SWCNT walls could be related to the defects introduced during the growth process.     

Reactivity of Single‐Walled Carbon Nanotubes in the Diels–Alder Cycloaddition Reaction: Distortion–Interaction Analysis along the Reaction Pathway

Diels–Alder cycloaddition is one of the most powerful tools for the functionalization of single‐walled carbon nanotubes (SWCNTs). Density functional theory at the B3‐LYP level of theory has been used to investigate the reactivity of different‐diameter SWCNTs (4–9,5) in Diels–Alder reactions with 1,3‐butadiene; the reactivity was found to decrease with increasing SWCNT diameter. Distortion/interaction analysis along the whole reaction pathway was found to be a better way to explore the reactivity of this type of reaction. The difference in interaction energy along the reaction pathway is larger than that of the corresponding distortion energy. However, the distortion energy plots for these reactions show the same trend. Therefore, the formation of the transition state can be determined from the interaction energy. A lower interaction energy leads to an earlier transition state, which indicates a lower activation energy. The computational results also indicate that the original distortion of the SWCNTs leads to an increase in the reactivity of the SWCNTs.     

Conducting π Columns of Highly Symmetric Coronene,The Smallest Fragment of Graphene

Coronene, which is the smallest D_6h‐symmetric polycyclic aromatic hydrocarbon, attracts particular attention as a basic component of electronic materials because it is the smallest fragment of graphene. However, carrier generation by physical methods, such as photo‐ or electric field‐effect, has barely been studied, primarily because of the poor π‐conduction pathway in pristine coronene solid. In this work we have developed unprecedented π‐stacking columns of cationic coronene molecules by electrochemical hole‐doping with polyoxometallate dianions. The face‐to‐face π–π interactions as well as the partially charged state lead to electrical conductivity at room temperature of up to 3 S cm^?1, which is more than 10 orders of magnitude higher than that of pristine coronene solid. Additionally, the robust π–π interactions strongly suppress the in‐plane rotation of the coronene molecules, which has allowed the first direct observation of the static Jahn–Teller distortion of cationic coronene molecules.