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141.
A. Filarowski A. Koll A. Kochel J. Kalenik P. E. Hansen 《Journal of Molecular Structure》2004,700(1-3):67-72
The crystal structures of two ortho-hydroxy ketones (5-chloro-2-hydroxyacetophenone (I K) and 3,5-dichloro-2-hydroxyacetophenone (II K)) have been determined with X-ray diffraction at 100 K. A comparison of steric effects on properties of pseudoaromatic hydrogen bonds in ortho-hydroxy acetophenone and ortho-hydroxy ketimines have been carried out with the application of crystallographic data.
Nuclear quadrupole resonance (NQR) spectra have been measured and interpreted. 相似文献
142.
143.
P. Pellegrino B. Garrido C. García R. Ferr J. A. Moreno J. R. Morante 《Physica E: Low-dimensional Systems and Nanostructures》2003,16(3-4):424
The ability of surface passivation to enhance the photoluminescence (PL) emission of Si nanocrystals in SiO2 has been investigated. Silicon precipitation in implanted samples takes place in a time scale of few minutes at 1100°C. For longer annealing at the same temperature, the PL intensity of the Si nanocrystals increases and eventually reaches saturation, while it correlates inversely with the amount of Si dangling bonds at the Si–SiO2 interface (Pb centers), as measured by electron spin resonance. This combined behavior is independent on the silica matrix properties, implantation profiles and annealing atmosphere and duration. The observation that the light emission enhancement is directly related to the annealing of Pb centers is confirmed by treatment in forming gas. This mild hydrogenation at much lower temperature (450°C) leads to a complete passivation of the Pb defects, increasing at the same time the PL yield and the lifetime. 相似文献
144.
假设13N是单粒子的2p态的结构,用Glauber多重散射理论计算了1GeV的质子在13N上弹性散射的微分截面,研究了13N的类晕结构.与13C的情况不同,虽然目前还没有关于p-13N弹性散射微分截面的实验材料与我们的理论结果相比较,但是这个理论结果可以作为对未来的实验测量工作的一个指导,特别是对兰州近代物理研究所的晕核实验研究工作有参考和指导价值.参照先前我们对13C晕核结构的理论预言和进而的实验证实,本文的计算结果清楚地表明:13N可能存在着一个类晕的质子皮结构.因此,实验上测量p-13N弹性散射的微分截面就是当前需要马上进行的一个实验研究工作. 相似文献
145.
Stochastic resonance is a statistical phenomenon that has been observed in periodically modulated, noise-driven, bistable systems. The characteristic signatures of the effect include an increase in the signal-to-noise of the output as noise is added to the system, and exponentially decreasing peaks in the probability density as a function of residence times in one state. Presented are the results of a numerical simulation where these same signatures were observed by adding achaotic driving term instead of a white noise term. Although the probability distributions of the noise and chaos inputs were significantly different, the stochastic and chaotic resonances were equal within the experimental error. 相似文献
146.
P. Tekely V. G rardy P. Palmas D. Canet A. Retournard 《Solid state nuclear magnetic resonance》1995,4(6):361-367
A simple modification of the standard cross-polarization method designed for quenching the proton T1ρ dependence when studying polarization transfer is presented. It is demonstrated that by using this simple procedure, new and subtle details of cross-polarization dynamics, previously hidden by the T1ρ(1H) effect, can be observed in dipolar-coupled spin systems. 相似文献
147.
Seventeen 1-aryl-2,2-dichlorocyclopropanes were examined by using IR, 13C NMR, and mass spectrometry. The data obtained from IR and 13C NMR spectra indicate that the bond strength of carbon-chlorine on the cyclopropane ring and the electron density of that carbon depend on the substituent. The mass fragmentation patterns of compounds in this series resemble those of the dibromo analogues. The fragmentation mechanism is proposed to involve the formation of indenium ion through an electrocyclization. 相似文献
148.
本文阐述了伺服系统结构设计中估算系统固有频率的必要性,介绍了一种分析和计算经纬仪方位伺服系统扭转振动固有频率的方法。 相似文献
149.
G. Carelli A. Di Siena N. Ioli A. Moretti G. Moruzzi F. Strumia 《International Journal of Infrared and Millimeter Waves》1994,15(4):619-633
We have measured the frequencies of four CH3OH far-infrared laser lines that were previously known only by wavelength measurement. Two of these lines turned out to be doublets, bringing the total number of measured lines to six. We can now confirm the assignments of five of them and definitely disprove the assignments proposed for the sixth.In particular we confirm the assignments for the four strong laser lines at 205 and 208 µm pumped by the 9-P(34) CO2 laser line. These lines share a common upper level in the first excited CO-stretch state, and terminate in the upper and lower levels of a hybrid state with J=5. Heterodyne frequency measurements and conventional microwave spectroscopy show that both lines are split into two components approximately 3.5 MHz apart. The origin of this further splitting is interpreted as a perturbed K-splitting.Work supported by Consiglio Nazionale delle Ricerche -Italia 相似文献
150.
This paper is concerned with a class of nonlinear delay partial difference equations with variable coefficients, which may
change sign. By making use of frequency measures, some new oscillatory criteria are established. This is the first time oscillation
of these partial difference equations is discussed by employing frequency measures.
相似文献