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准分子激光束的喇曼组束 总被引:5,自引:3,他引:2
受激喇曼散射可以将紫外准分子激光辐射频移到特定的近紫外或可见光波长,采用喇曼整形技术可以改善斯托克斯光的光束质量,本文报道喇曼组束提高喇曼整形效率的实验结果. 相似文献
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由于部分离化激光等离子体中存在束缚电子,它可显著改变其参量不稳定性。本文分析了部分离化激光等离子体的受激喇曼散射的非线性色散关系,计算了钕玻璃倍频和三倍频激光受激喇曼散射的增长率,结果表明,前向受激喇曼散射显著增强,后向受激喇曼散射影响不大。 相似文献
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从声子-电磁激元频率色散关系的普遍公式出发,推导出了单轴晶体的Merten方程和电磁激元的频率色散关系。测量了BaTiO3和Ce:BaTiO3晶体的简正模和斜声子的喇曼散射谱,并根据Merten方程,拟合出了斜声子的方向色散曲线;记录了A1类电磁激元在不同波矢值下的喇曼谱,观察到其频率色散现象.根据以上结果,对A1(TO)模喇曼谱中两个宽的非对称峰的归属和BaTiO3晶体的结构相变机制进行了讨论;计算出了这两种晶体的受夹介电常数;分析了掺Ce对BaTiO3晶体结构的影响。
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I. N. Flerov M. V. Gorev V. D. Fokina M. S. Molokeev A. D. Vasil’ev A. F. Bovina N. M. Laptash 《Physics of the Solid State》2006,48(8):1559-1567
The heat capacity, T-p phase diagrams, and unit cell parameters of cryolite (NH4)3Ti(O2)F5 were studied over a wide temperature range. A phase transition was found near 226 K, and its thermodynamic characteristics and their dependence on the crystallization conditions were determined. The coordinates and thermal parameters of atoms in the Fm3m phase were refined. An analysis of the electron density distribution and the transition entropy showed that the mechanism of the structural transition involves, above all, rotation of the Ti(O2)F5 octahedra. Possible models of disordering of tetrahedral ammonium groups are considered. 相似文献
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A.A. Lavrentyev P.N. Shkumat T.N. Bondarenko O.Yu. Khyzhun M.V. Karpets 《Journal of Physics and Chemistry of Solids》2011,72(2):83-89
Total and partial densities of states of the constituent atoms of ZrTiO4 and HfTiO4 titanates have been calculated using a self-consistent cluster method as incorporated in the FEFF8 code. The calculations reveal the similarity of the electronic structure of both titanates and indicate that the valence band of the compounds under consideration is dominated by contributions of O 2p states. These states contribute throughout the whole valence-band region; however their maximum contributions occur in the upper portion of the band. Other significant contributors in the valence-band region are Ti 3d and Zr 4d states in ZrTiO4 and Ti 3d and Hf 5d states in HfTiO4. All the above d-like states contribute throughout the whole valence-band region of the titanates; however maximum contributions of the Ti 3d states occur in the upper portion, whilst those of the Zr 4d (Hf 5d) states are in the central portions of the valence band. The FEFF8 calculations render that the bottom of the conduction band of ZrTiO4 and HfTiO4 is dominated by contributions of Ti 3d? states, with also smaller contributions of Zr 4d?/Hf 5d? and O 2p? states. To verify the above FEFF8 data, the X-ray emission bands, representing the energy distributions of mainly O 2p, Ti 3d and Zr 4d states, were measured and compared on a common energy scale. These experimental data are found to be in agreement with the theoretical FEFF8 results for the electronic structure of ZrTiO4 and HfTiO4 titanates. Additionally, X-ray photoelectron valence-band and core-level spectra were recorded for the constituent atoms of the titanates under study. 相似文献
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The effect of low pressure radio frequency (rf) plasma treatment on TiO2 surface states has been studied using X-ray photoelectron spectroscopy. Three different oxidation states of oxygen in untreated TiO2 powder were observed, which suggests the existence of adsorbed water and carbon on the surface. The ratio of oxygen to titanium (O/Ti) was decreased for the low ion dose plasma treated samples due to desorption of water from the surface. In the case of Ti 2p about 20% of surface states were converted to Ti3+ 2p3/2 state after plasma treatment with a very good stability, whereas untreated TiO2 remained mostly as Ti4+ state. A rapid decrease in the ratio of carbon to titanium (C/Ti) at TiO2 surface was also observed after plasma treatment and more than 90% of carbon atoms were removed from the surface. Therefore, the plasma treatment of TiO2 has advantages to surface carbon cleaning, increasing O− and Ti3+ surface states, hence improving the activity of TiO2 for different environmental, energy and biological applications. 相似文献
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《Infrared physics》1978,18(5-6):901-908
Far-infrared measurements (17–170 cm−1) are reported for SrF2:RE3+ (RE = Pr, Nd, Tb, Dy, Ho, Er, Tm).The vibrations of the F−i compensation ions reveal the local symmetry (Oh, C4v, C3v). The concentration of ions in each local site and the frequencies of the F−i vibrations in the C4v site show a regular evolution vs RE ionic radii.The study of electronic transitions within the ground manifold of the RE ions shows a similar evolution. For Dy3+ we detect lines already attributed to C3v (F−i) sites. New lines observed with Er3+ and Dy3+ can be attributed to C4v (F−i) sites, and the crystal field parameters that we have calculated are close to those of the C4v (F−i) site in CaF2.For Nd3+ the electronic line is close to a C4v level observed by EPR. 相似文献
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Effect of composition on the structure, spontaneous and stimulated emission probabilities of various 1.0 mol% Tm2O3 doped (1−x)TeO2+(x)WO3 glasses were investigated using Raman spectroscopy, ultraviolet-visible-near-infrared (UV/VIS/NIR) absorption and luminescence measurements.Absorption measurements in the UV/VIS/NIR region were used to determine spontaneous emission probabilities for the 4f-4f transitions of Tm3+ ions. Six absorption bands corresponding to the absorption of the 1G4, 3F2, 3F3 and 3F4, 3H5 and 3H4 levels from the 3H6 ground level were observed. Integrated absorption cross-section of each band except that of 3H5 level was found to vary with the glass composition. Luminescence spectra of the samples were measured upon 457.9 nm excitation. Three emission bands centered at 476 nm (1G4→3H6 transition), 651 nm (1G4→3H4 transition) and 800 nm (1G4→3H5 transition) were observed. Spontaneous emission cross-sections together with the luminescence spectra measured upon 457.9 nm excitation were used to determine the stimulated emission cross-sections of these emissions.The effect of glass composition on the Judd-Ofelt parameters and therefore on the spontaneous and the stimulated emission cross-sections for the metastable levels of Tm3+ ions were discussed in detail. The effect of temperature on the stimulated emission cross-sections for the emissions observed upon 457.9 nm excitation was also discussed. 相似文献
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By means of a Fabry-Pérot-interferometer the hyperfine structure of 10 lines of the Eu-II-spectrum was analysed and from the results splitting factors and isotope shifts were calculated. When evaluating the magnetic momentμ, of Eu1 1 it was found that the two ground states (a9S 4 0 and a7S 3 0 ) of the Eu-II yield two distinctly different values for μ. This discrepancy can be removed assuming that a different electronic splitting factor (a6 s) has to be attributed to the 6s-electron in each of these two states. 相似文献
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The lifetimes of atomic CoI states have been determined using the delayed coincidence technique. A tunable dye laser pumped by a nitrogen laser was employed for the excitation of cobalt atoms in an atomic beam. The lifetimes were derived from the time dependent fluorescence intensity of the observed lines after the excitation. For the measurement of the lifetimes of thee 4 F 9/2,f 4 F 9/2 andf 4 F 7/2 levels a two step excitation was applied. In case of overlapping measurement we find our results to be in good agreement with those reported by Becker [1]. 相似文献
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Visible light emission from atoms and ions sputtered on a polycrystalline Ti surface was observed under irradiation of 30 keV Ar3+ ions. A number of atomic lines of Ti I and II were observed in the wavelength of 250-850 nm. The intensity of Ti II emission increased 1.3-5.6 times by introducing oxygen molecules at a pressure of 5.8 × 10−5 Pa, whereas that of Ti I decreased 0.5-0.8 times. Factors enhancing or reducing photon intensities were plotted as a function of energy of the corresponding electrons in the excited states for Ti atoms and Ti+ ions. 相似文献
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Resonances corresponding to the matching of laser mode intervals with Lapmor precessional frequencies have been oberved in the discharge current for four transitions in the spectrum of atomic Zr, introduced into a gas discharge by cathodic sputtering. Signals were observed for lower as well as for upper levels. The measured g-factors for the states 4d25s(a4F)5p 3F2,3,4 and 4d25s(a2P)5P 3P2 are symmetrically higher than values given in the literature. 相似文献