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951.
Hongnian Li Yabo Xu Shining Bao Haiyang Li Peimo He Haijie Qian Fengqin Liu Yibulaxi Kuirexi 《中国科学A辑(英文版)》2000,43(11):1189-1194
K3C60, single crystal film was prepared on the cleaved (111) surface of C60, single crystal. Synchrotron radiation angle-resolved photoemission spectra were measured at normal emission with sample temperature at × 150K. Up to four subpeaks of LUMO-derived band were observed. These sub-peaks exhibit distinct energy dispersions which resemble in general the theoretical ones calculated for K3C60 at low temperature with the so-called one-dimensional disordered structure. But there is large deviation of experimental sub-band intervals from the theoretical values. This result is meaningful for the studies of the physical properties of alkali-doped C60 solids, e.g. the mechanism for superconductivity. 相似文献
952.
通过对香豆素343(C343)在不同溶剂中的稳态吸收光谱、稳态荧光光谱和时间分辨荧光光谱的分析,研究了溶剂对C343的光谱性质的影响,并获得了光谱特性与溶剂极性之间的依赖关系. 吸收光谱峰值的红移随着溶剂极性的增加而发生较小的变化. 然而,荧光光谱的峰值对溶剂的极性却很敏感,并随着溶剂极性参数f(ε,n)的增加呈线性增长. 这是由于C343激发态电荷分布的变化导致了它在极性溶剂中第一激发单重态能级的变化. 用溶剂效应测量法和量子化学计算方法确定了C343最低激发态的偶极矩,这两方法所得的结果一致. C343在不同溶剂中的时间分辨荧光光谱研究表明荧光寿命随着溶剂极性的增加而增加,即从甲苯溶液的3.09 ns线性地增加到水溶液中4.45 ns;荧光寿命延长的根源可归因于C343与氢键给体溶剂之间的分子间氢键相互作用. 相似文献
953.
利用高精度从头算能量点构建三重态3A' 势能面. 单点能计算采用的方法是完全活性空间自洽场和多组态相互作用,计算中所用的基组是aug-cc-pV5Z,并利用多体展开方法结合AP函数形式对所有能量点进行了拟合. 在新构建的势能面基础上,在平动能0.8~2.2 eV进行了含时波包散射计算,计算中同时采用了离心突然近似和紧耦合方法. 另外还对初始振动态ν=0~3(j=0)情况下的总反应几率进行了计算,结果发现初始振动激发对该体系有很大的增强作用. 相似文献
954.
S.-K. Wang W.-C. Tsai L.-C. Chou J. Chen Y.-H. Wu T.-M. He K.-S. Feng C.-R. Wen 《Surface science》2012,606(13-14):1062-1070
Continuous-time photoelectron spectroscopy (PES) and continuous-time core-level photon-stimulated desorption (PSD) spectroscopy were used to study the monochromatic soft X-ray-induced reactions of CCl2F2 molecules adsorbed on Si(111)-7 × 7 at 30 K (CCl2F2 dose = 2.0 × 1014 molecules/cm2, ~ 0.75 monolayer) near the Si(2p) core level. Evolution of adsorbed CCl2F2 molecules was monitored by using continuous-time photoelectron spectroscopy at two photon energies of 98 and 120 eV to deduce the photolysis cross section as a function of energy. It was found that the photolysis cross sections for 98 and 120 eV photons are ~1.4 × 10? 18 and ~ 8.0 × 10? 18 cm2, respectively. Sequential F+ PSD spectra obtained by using continuous-time core-level photon-stimulated desorption spectroscopy in the photon energy range of 98–110 eV show the variation of their shapes with photon exposure and depict the formation of surface SiF species. The dissociation of CCl2F2 molecules adsorbed on Si(111)-7 × 7, irradiated by monochromatic soft X-ray in the photon energy range of 98–110 eV, is mainly due to dissociative electron attachment and indirect dipolar dissociation induced by photoelectrons emitted from the silicon surface. 相似文献
955.
Liu-Niu Tong Yi-Chao Wang Xian-Mei He Huai-Bin Han Ai-Lin Xia Jin-Lian Hu 《Journal of magnetism and magnetic materials》2012
We explore the effects of hydrogen annealing on the room temperature ferromagnetism and optical properties of Cr-doped ZnO nanoparticles synthesized by the sol-gel method. X-ray diffraction and x-ray photoelectron spectroscopy data show evidence that Cr has been incorporated into the wurtzite ZnO lattice as Cr2+ ions substituting for Zn2+ ions without any detectable secondary phase in as-synthesized Zn0.97Cr0.03O nanopowders. The room temperature magnetization measurements reveal a large enhancement of saturation magnetization Ms as well as an increase of coercivity of H2-annealed Zn0.97Cr0.03O:H samples. It is found that the field-cooled magnetization curves as a function of temperature from 40 to 400 K can be well fitted by a combination of a standard Bloch spin-wave model and Curie–Weiss law. The values of the fitted parameters of the ferromagnetic exchange interaction constant a and the Curie constant C of H2-annealed Zn0.97Cr0.03O:H nanoparticles are almost doubled upon H2-annealing. Photoluminescence measurements show evidence that the shallow donor defect or/and defect complexes such as hydrogen occupying an oxygen vacancy Ho may play an important role in the origin of H2-annealing induced enhancement of ferromagnetism in Cr-H codoped ZnO nanoparticles. 相似文献
956.
Qiaolin He 《advances in applied mathematics and mechanics.》2012,4(2):238-249
In this paper, we propose a new two-level preconditioned C-G method
which uses the quadratic smoothing and the linear correction in distorted but topologically
structured grid. The CPU time of this method is less than that of the
multigrid preconditioned C-G method (MGCG) using the quadratic element, but
their accuracy is almost the same. Numerical experiments and eigenvalue analysis
are given and the results show that the proposed two-level preconditioned method
is efficient. 相似文献
957.
为达到合肥光源二期工程通用模式的设计流强,在储存环上选择垂直方向β函数比较大的位置增加一组八极磁铁。该组八极磁铁对水平方向动力学孔径影响很小,虽然垂直方向动力学孔径明显减小,但仍然大于物理孔径,不会影响束流的注入积累过程。该组八极磁铁产生的垂直方向振荡频率分散可以提供ms量级的Landau阻尼时间,将明显增强抑制垂直方向束流集体不稳定性的能力。该组八极磁铁投入运行后,合肥光源注入积累过程明显改善,注入流强从无八极磁铁时的约100 mA提高到330 mA左右。 相似文献
958.
During laser spectroscopic measurement, a part of laser energy will be converted into heat in the processes of excitation and light emission. Temperature monitoring can help to evaluate such nonradiative process. Upconversion luminescence of phosphor Y2O3:Er,Yb under laser excitation at 980 nm was investigated in this work. Point temperature of the phosphor was monitored using the fluorescent intensity ratio (FIR) technology. Laser induced temperature rising was identified by comparison with a theoretically ideal temperature calibration function: lnR = 3.1738–1167/T. The monitored temperature of laser heating rises monotonically with increasing laser power. Circumstances around heating point will modify the calibration function, but the linear slope of lnR ~ 1/T is constant. 相似文献
959.
Yingji He Xing Zhu Dumitru Mihalache Jinglin Liu Zhanxu Chen 《Optics Communications》2012,285(15):3320-3324
We study the existence and stability of solitons forming in PT–symmetric optical lattices with spatially periodic modulation of the local strength of the nonlinear media. We found that the spatial modulation of the nonlinearity significantly affects the stability of solitons in PT–symmetric optical lattices. With the decrease of the strength of nonlinear refractive index modulation, the soliton's stability domain increases, whereas with the increase of the period of nonlinear refractive index modulation, the corresponding soliton's stability range narrows. In addition, we also investigate the influence of variation of the amplitude of the linear PT–symmetric lattice potential on soliton dynamics, in the presence of spatially periodic modulation of nonlinearity. 相似文献
960.
Crystal structure and thermochemical properties of bis(1-octylammonium) tetrachlorochromate phase change materials 下载免费PDF全文
A new crystalline complex(C8 H17 NH3) 2 CdCl 4(s)(abbreviated as C8Cd(s)) is synthesized by liquid phase reaction.The crystal structure and composition of the complex are determined by single crystal X-ray diffraction,chemical analysis,and elementary analysis.It is triclinic,the space group is P-1 and Z = 2.The lattice potential energy of the title complex is calculated to be U POT(C 8 Cd(s))=978.83 kJ·mol-1 from crystallographic data.Low-temperature heat capacities of the complex are measured by using a precision automatic adiabatic calorimeter over a temperature range from 78 K to 384 K.The temperature,molar enthalpy,and entropy of the phase transition for the complex are determined to be 307.3±0.15 K,10.15±0.23 kJ·mol-1,and 33.05±0.78 J·K-1 ·mol-1 respectively for the endothermic peak.Two polynomial equations of the heat capacities each as a function of temperature are fitted by using the leastsquare method.Smoothed heat capacity and thermodynamic functions of the complex are calculated based on the fitted polynomials. 相似文献