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991.
通过广义的Laguerre类型轨道,在组态相互作用框架内,发展了一套从头计算程序,来研究原子中的电子结构.应用该程序,通过计算能量最小值,求出最优波函数.利用优化波函数的单电子密度分布和角双电子密度的最可几分布,研究了处于最低激发态的Be,B,C,N,O,Ne原子的sαpβ组态的几何活性原子态GAAS(geometricallyactive atomic state).结果显示,作为原子波函数的内禀性质,双电子密度最可几角分布的角度与通常由分子杂化轨道理论解释的相关原子的分子的结合键角近似相等. 相似文献
992.
993.
研究了不同密度和厚度的碳气凝胶薄片的制备及其表面致密层去除工艺。在以间苯二酚、甲醛为原料制备有机及碳气凝胶块体材料的基础上,结合自制活动式微模具成型工艺,制备了厚度在80~350 μm,密度在50~600 mg·cm-3范围内变化的碳气凝胶薄片。采用场发射扫描电镜、X射线相衬成像和表面轮廓仪-台阶仪等手段对其表面和内部微观结构进行了表征。测试结果表明,碳气凝胶薄片与块体的内部结构相同,但薄片表面存在一层和内部结构截然不同的致密层。采用不同粗糙程度的材料对薄片进行了表面微处理,成功去除该致密“皮”层。 相似文献
994.
995.
We study J/psi production at RHIC and LHC energies with both initial production at energies reached and the BNL Relativistic Heavy Ion Collider (RHIC) and CERN Large Hadron Collider (LHC) with regeneration. We solve the coupled set of transport equations for the J/psi distribution in phase space and the hydrodynamic equation for evolution of quark-gluon plasma. At RHIC, continuous regeneration is crucial for the J/psi momentum distribution while the elliptic flow is still dominated by initial production. At energies reached at the LHC energy, almost all the initially created J/psis are dissociated in the medium and regeneration dominates the J/psi properties. 相似文献
996.
Y. Q. Zheng H. Y. Zhu L. X. Huang H. B. Chen Y. M. Duan R. B. Su C. H. Huang Y. Wei J. Zhuang G. Zhang 《Laser Physics》2010,20(4):756-760
A LD end-pumped acoustic-optic Q-switched intracavity frequency-doubled Nd:YVO4 laser was demonstrated. It uses a high gray-tracking resistance KTP crystal as nonlinear optical crystal. The output characteristics
of 532 nm green laser using different doping concentrations and cavity configurations were investigated. With the pump power
of 27.5 W, a maximum average power of 13 W at 532 nm was achieved at a pulse repetition rate of 80 kHz, corresponding to the
optical-to-optical efficiency of 47.3%. The pulse width is 30 ns and single pulse energy is up to 162.5 μJ. This work is a
significant exploration for using a high gray-tracking resistance KTP crystal to generate highly efficient frequency-doubled
green laser. 相似文献
997.
998.
Yufeng Zhai Guiyan Liu Fenchun Jin Yingying Zhang Xuefang Gong Zhuang Miao Jinheng Li Mengyao Zhang Yumeng Cui Lingyan Zhang Yu Liu Huixin Zhang Yanli Zhao Yongfei Zeng 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(49):17843-17847
Covalent‐organic frameworks (COFs) as porous crystalline materials show promising potential applications. However, developing facile strategies for the construction of COFs directly from amorphous covalent organic polymers (COPs) is still a great challenge. To this end, we report a novel approach for easy preparation of COFs from amorphous COPs through the linkage replacement under different types of reactions. Four COFs with high crystallinity and porosity were constructed via the linkage substitution of polyimide‐linked COPs to imine‐linked COFs as well as imine‐linked COPs to polyimide‐linked COFs. The realization of the linkage substitution would significantly expand the research scope of COFs. 相似文献
999.
An efficient and convenient method for the synthesis of various substituted pyrano[3,2-c]chromene-2,5-diones was developed via the I2-promoted tandem cyclization of commercially available aryl methyl ketones and 4-hydroxycoumarins. Preliminary mechanism studies indicated that the reaction involved a consecutive iodination/Kornblum oxidation/annulation process. HI produced in the I2-DMSO system acted as an important promoter, accelerating the annulation protocol. 相似文献
1000.
Longzhou Zhang Yi Jia Hongli Liu Linzhou Zhuang Xuecheng Yan Chengguang Lang Xin Wang Dongjiang Yang Keke Huang Shouhua Feng Xiangdong Yao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(28):9504-9508
Atomic metal species‐based catalysts (AMCs) show remarkable possibilities in various catalytic reactions. The coordination configuration of the metal atoms has been widely recognized as the determining factor to the electronic structure and the catalytic activity. However, the synergistic effect between the adjacent layers of the multilayered AMCs is always neglected. We reported an atomic Co and Pt co‐trapped carbon catalyst, which exhibits a ultrahigh activity for HER in the wide range of pH (η10=27 and 50 mV in acidic and alkaline media, respectively) with ultralow metal loadings (1.72 and 0.16 wt % for Co and Pt, respectively), which is much superior to the commercial Pt/C. Theoretical analysis reveals that the atomic metals on the inner graphitic layers significantly alter the electronic structure of the outmost layer, thus tailoring the HER activity. This finding arouses a re‐thinking of the intrinsic activity origins of AMCs and suggests a new avenue in the structure design of AMCs. 相似文献