不同组分的钒酸盐混晶Ybt:YxGd1-t-xVO4光谱与激光性质的比较研究

研究了三种掺Yb钒酸盐混晶Yb_0.005:Y_0.298Gd_0.697VO₄, Yb_0.007:Y_0.407Gd_0.586VO₄和Yb_0.009:Y_0.575Gd_0.416VO₄的室温偏振吸收谱和发射谱. 结果表明,最强的吸收和发射相应于π偏振,位 关键词： 掺Yb钒酸盐混晶 吸收谱和发射谱 激光振荡 偏振态     

不需制备样品与获得期望强度的红外单光束谱

为扣除溶剂或其他背景组分的干扰,测量红外光谱时常常需要获得期望强度的高质量背景单光束谱。通常,实验上获得期望强度的背景谱是极其困难的。为实现这一重要且十分困难的目标,引进了杂化单光束谱的概念。同一溶液但不同厚度的b₁和b₂的两样品的单光束谱分别为Φ_b1和Φ_b2,则定义它们的线性组合Φ_α=αΦ_b1+(1-α)Φ_b2为杂化单光束谱,其中α(0≤α≤1)称为组分因子。调整组分因子α数值,就可以精确调控杂化谱的强度。在合适的条件下,杂化谱Φ_α与厚度为b₂-αb₂+αb₁的真实样品的光谱高度类似,即Φ_b2-αb2+αb1≈Φ_α。因此,不用制备厚度为b₂-αb₂+αb₁的样品,其单光束谱可以用Φ_α来替代。随着α变化,可以得到不同的Φ_α,厚度在b₁和b₂间的真实样品的单光束谱都可用相应的Φ_α来替代。实验结果证实,杂化谱提供了一种简单和易操作的扣除背景干扰的高效方法。     

基于光声光谱技术的1.5 μm波段 NH3吸收谱线测量与分析

NH₃的检测具有广泛的应用,采用光声法检测NH₃是当前研究的热点,而确定NH₃的吸收谱线则是实现光声法检测NH₃的前提。采用外腔可调谐半导体激光器构造了光声气体检测系统,检测了NH₃的近红外吸收谱线,获得了常温常压下NH₃在1 515~1 532 nm范围内的吸收光谱。实验确认了NH₃在1 515.2,1 516.0,1 518.0,1 519.9,1 522.4,1 527.0,1 531.7 nm处存在强吸收。HITRAN 2004光谱数据库在近红外1.5 μm波段NH₃的吸收谱线数据未见报道,该结果为研究光声法检测NH₃提供了更多可选择的吸收谱线。     

MoO3/Al2O3催化剂中Mo分散的正电子研究

用浸渍法制备了一系列不同Mo含量的MoO₃/Al₂O₃催化剂.测量了这些样品的正电子湮没寿命谱(PALS)与符合多普勒展宽(CDB)谱,以研究其孔洞结构以及Mo分散.正电子寿命测量结果表明,Al₂O₃载体中存在两种不同尺寸的孔洞.掺入MoO₃之后,Mo原子主要进入Al₂O₃的大孔中,使孔洞体积减小.符合多普勒展宽谱结果表明,当MoO 关键词： 3/Al₂O₃催化剂')" href="#">MoO₃/Al₂O₃催化剂 正电子湮没寿命谱 符合多普勒展宽 Mo 分散     

Cu(Ⅱ)及Zn(Ⅱ)与直链醚席夫碱配合物的合成与表征

合成了两种直链醚席夫碱双水杨醛缩二甘醇二胺(SALDA)和双水杨醛缩四甘醇二胺(SALTTA)及其新配合物[Zn(SALDA)](NO₃)₂·4H₂O和[Cu₃(SALTTA)(NO₃)₄](NO₃)₂·3H₂O.并以IR谱、UV谱,特别是¹H和¹³C NMR谱等方法进行了表征,并详细地讨论了合成方法,IR谱表明SALTTA中醚氧并未全部配位.     

MoO3在多孔γ-Al2 O3中固熔分散的研究

用MoO₃与多孔γ-Al₂O₃载体以机械混合法制备了一系列MoO₃/γ-Al₂O₃样品.用扫描电子显微镜、X射线衍射、X射线光电子能谱分析、综合热分析(TG/DTA)和正电子湮没谱学研究了MoO₃加载于γ-Al₂O₃后固熔分散过程.分别测量了不同含量的MoO₃/γ-Al_{2关键词： 正电子湮没谱学 三氧化钼 分散 逐次加载}     

自由基分子NH2ν2带CO激光磁共振π谱的观测

采用高灵敏度、高分辨率激光磁共振光谱(LMR)方法在6μm谱段测量了自由基分子NH₂ν₂带的π谱(ΔM_J=0).测量了前人已测过的谱,结果与之较好符合.并观测到了前人没有观测过的新谱,在3支激光谱线下共获得约13支塞曼(Zeeman)跃迁谱线,其中在2支激光谱线下新测得的谱线10支.利用我们已经测得的^[8]σ谱的新的共振谱线的数值和已取得的激光磁共振谱线的标识方法,可预期得到NH₂的一些新的分子参数.     

液芯光纤中溶液吸收和荧光的性质对CS2受激拉曼散射阈值的影响

利用液芯光纤技术研究了不同浓度的β-Carotene的CS₂溶液的吸收与荧光的特性对CS₂的一、二阶Stokes谱线阈值的影响.实验发现随溶液浓度(10^-8—10^-6 mol/L)增加，CS₂的一阶Stokes谱线的激发阈值相对变高；并且与纯CS₂芯液的受激拉曼散射相比较，在低抽运能量激发下，就观察到CS₂的二阶Stokes谱线.这主要是由于在CS₂的受激拉曼谱线产生的过程中，β-Carotene的CS₂溶液的吸收和荧光共同影响了CS₂的一、二阶Stokes谱线的阈值.我们进行了理论上的拟合与分析，其结果与实验符合很好. 关键词： 2受激拉曼散射阈值')" href="#">CS₂受激拉曼散射阈值 液芯光纤 吸收与荧光     

铁基非晶态因瓦合金的声子谱研究

用非弹性中子散射实验方法研究了非晶态Ｆｅ_９０－ｘＣｏ_ｘＺｒ_１０（ｘ＝１０，４０）和Ｆｅ_８０－ｙＣｒ_ｙＰ_１３Ｃ_７（ｙ＝４，８）合金的广义声子谱，在低能区域（?ω≤２０ｍｅＶ）观察到了与因瓦效应相关的声子谱软化现象。初步讨论了这种动力学方面的反常行为。结果表明，声子谱软化可能与在因瓦合金中存在增强的电子－声子相互作用有关。 关键词：     

不同含氮量的a-Si:H/a-SiNx:H超晶格界面性质的研究

通过电调制吸收、光热偏转谱、光致发光及红外吸收谱等实验技术,研究了不同含氮量的a-Si:H/a-SiN_x:H超晶格的界面性质。由电调制吸收测试得出的界面电荷密度Q_s～10¹²cm^-2。Q_s比由光热偏转谱所获得的界面态密度N_i～10¹¹cm^-2大出约半个数量级。N_i,Q_s,及光致发光相对峰值 关键词：     

Site-specific valence-band X-ray photoelectron spectra of a SrTiO3 single-crystal by X-ray standing wave technique

Site-specific valence-band X-ray photoelectron spectra of SrTiO₃ (111) were successfully obtained by using X-ray standing wave technique. Contributions of the Ti and SrO₃ derived states to the valence-band spectra were clearly separated. The spectra provided not only site-specific but also bulk-sensitive information on the SrTiO₃ crystal because of the use of a high-energy synchrotron X-ray source (hν=4750 eV) for photoelectron excitation with the large escape depth. The electronic structures calculated by the DV-Xα method using a (Sr₈Ti₂₇O₁₀₈)⁹²⁻ cluster model well reproduced the observed structures in the valence-band spectra. The partial density of states of both Ti and Sr ions in SrTiO₃ were mainly distributed over the bottom of the valence-band to produce the covalent bonding with O ions.     

Resonant photoemission spectroscopy study of electronic structures of LiMn2O4

The valence-band resonant photoemission spectra (RPES) of LiMn₂O₄ have been measured throughout the Mn3p absorption edge. Based on the RPES data, the contribution of Mn3d states to the valence band of LiMn₂O₄ has been described and, consequently, the detailed hybridization between O2p and Mn3d states in the valence-band was determined.     

Photoemission from Ag-clusters in a C60 matrix

Ag-clusters with a narrow size distribution around 2.8 ± 0.5 nm in diameter have been produced by a supersonic-beam technique and embedded into a matrix of solid C₆₀. Photoelectron spectra of the valence-band region do not confirm a large charge transfer between the Ag clusters and the C₆₀ matrix. No plasmon feature is detected in the spectra of the Ag-3d core level of the Ag-clusters.     

Electronic structure of β-RbNd(MoO4)2 by XPS and XES

β-RbNd(MoO₄)₂ microplates have been prepared by the multistage solid state synthesis method. The phase composition and micromorphology of the final product have been evaluated by XRD and SEM methods. The electronic structure of β-RbNd(MoO₄)₂ molybdate has been studied employing the X-ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (XES). For the molybdate, the XPS core-level and valence-band spectra, as well as XES bands representing energy distribution of the Mo 4d- and O 2p-like states, have been measured. It has been established that the O 2p-like states contribute mainly to the upper portion of the valence band with also significant contributions throughout the whole valence-band region. The Mo 4d-like states contribute mainly to a lower valence band portion.     

Electronic structure of ZrTiO4 and HfTiO4: Self-consistent cluster calculations and X-ray spectroscopy studies

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.     

Energy loss spectra of low primary energy (E0 ? 1 keV) electrons backscattered by silicon dioxide

A Monte Carlo simulation is described and utilized to calculate the energy distribution spectra of the electrons backscattered by silicon dioxide. Spectra are presented for incident energies of 250 eV, 500 eV, and 1000 eV. Spectra interpretation is based on a semiquantitative valence-band structure model for SiO₂ crystals.     

Optical characterization of gallium antimonide highly doped with manganese

Gallium antimonide crystals highly doped with Mn were prepared by a liquid-phase-electroepitaxy growth method. The crystals exhibited high hole concentrations up to 6×10¹⁸ cm⁻³. Photoluminescence (PL) and transmission techniques were used for their investigation. Spectral line-shapes typical for highly doped semiconductors were observed. The lines revealed the features corresponding to band gap narrowing and valence-band filling phenomena. Values of the band-gap narrowing ΔE_g and the degree of the valence-band filling ΔE_F were estimated from the PL spectra. The ionization energy of the Mn acceptor E_i was estimated to be approximately 15.1-15.6 meV. At low temperatures, the PL maxima shifted relatively strongly towards higher energy with temperature. The shifts most probably resulted from a dramatic change in the electron density of states near the bottom of the conduction band. The extent of low-energy tails of the PL bands correlates with the doping levels. The transmission spectra exhibited an absorption band centred at around 774-780 meV. The band most probably originated in electron transitions from the level of spin-orbit splitting to the top of the valence band.     

Electrophysical properties and electronic structure of tin-doped antimony telluride

The effect of Sn atoms on the electrophysical properties and x-ray photoelectron spectra of Czochralski-grown Sb₂Te₃ single crystals is studied. The character of the temperature dependences of the kinetic coefficients is shown to depend noticeably on the structure of the valence band, which consists of two valence subbands. Estimates of the effective density-of-states masses of holes and of the gap between the valence-band extrema in Sb₂Te₃: Sn agree with the data available for the Sb₂Te₃ not doped with tin. X-ray photoelectron spectra of Sb₂Te₃: Sn single crystals do not exhibit noticeable core-level shifts and electron density redistribution in the valence band.     

Valence transition of YbInCu4 observed in hard X-ray photoemission spectra

Yb 3d and valence-band photoemission spectra of the first-order valence-transition compound YbInCu4 have been measured with hard x ray at an excitation energy of 5.95 keV. Abrupt changes are clearly observed in both spectra around the transition temperature T(V)=42 K, in comparison with ultraviolet and soft x-ray photoemission (VUV-PES and SX-PES) spectra. From the Yb 3d spectra, the Yb valence has been estimated to be approximately 2.90 from 220 down to 50 K and approximately 2.74 at 30-10 K. We propose that Yb 3d hard x-ray photoemission spectroscopy is a very powerful method to estimate the valence of Yb with high accuracy. On the other hand, the Yb2+ 4f-derived peaks in the valence-band spectra exhibit a remarkable enhancement below T(V). The shape of the valence-band spectra is different from those of the VUV-PES and SX-PES spectra above T(V), reflecting the In 5s and 5p contributions.     

Screening channels in 4f photoemission from light rare earth compounds

The results of valence-band photoemission measurements at the giant 4d-4f resonance are reported for the REIr₂ and RERh₂ series of compounds with RE = Ce, Pr, Nd. Double peaked structures in the 4f derived photoemission spectra are observed in all cases, with roughly constant separation between the two peaks. We propose that the peak closest to the Fermi level results from the occupation of a 4f/5d hybridized screening orbital, with decreasing 4f weight from Ce to Nd systems.