The ν3 and 2ν3 bands of SO3, SO3, SO3, and SO3

This sixth of a series of publications on the high-resolution rotation-vibration spectra of sulfur trioxide reports the results of a systematic study of the ν₃ and 2ν₃ infrared bands of the four symmetric top isotopomers ³²S¹⁶O₃, ³²S¹⁸O₃, ³⁴S¹⁶O₃, and ³⁴S¹⁸O₃. An internal coupling between the l=0(A₁^′) and l=2(E^′) levels of the 2ν₃ states was observed. This small perturbation results in a level crossing between |k−l|=9 and 12, in consequence of which the band origins of the A₁^′,l=0 “ghost” states could be determined to a high degree of accuracy. Ground and upper state rotational constants as well as vibrational anharmonicity constants are reported. The constants for the center-of-mass substituted species ³²S¹⁶O₃ and ³⁴S¹⁶O₃ vary only slightly, as do the constants for the ³²S¹⁸O₃, ³⁴S¹⁸O₃ pair. The S-O bond lengths for the vibrational ground states of the species ³²S¹⁶O₃, ³⁴S¹⁶O₃, ³²S¹⁸O₃, and ³⁴S¹⁸O₃ are, respectively, 141.981 99(1), 141.979 38(6), 141.972 78(8), and 141.969 93(8) pm, where the uncertainties, given in parentheses, are two standard deviations and refer to the last digits of the associated quantity.     

Optical conductivity of CePd3, YPd3 and PrPd3

The optical conductivity of intermediate valence CePd₃ at 300 K exhibits a maximum near 16 meV, which is absent in the reference materials YPd₃ and PrPd₃. Using a modified Drude model with a memory function ansatz this anomaly has been identified as a resonant electron-electron scattering process of conduction electrons at the localized 4f states near the Fermi level E_F. The model fit gives estimates of the width of the 4f states, of their separation from E_F and of the f-d hybridization energy. Intra-4f transitions of CePd₃ are stronger compared to those of PrPd₃ due to the stronger f-d hybirdization. 4d→4f transition energies of CePd₃ are reduced due to an electron-hole Coulomb binding energy.     

The first-principles study of ferroelectric behaviours of PbTiO3/SrTiO3 and BaTiOn/SrTiO3 superlattices

We have performed the first-principles calculation to investigate the origins of ferroelectricities and different po- larization behaviours of superlattices BaTiO3/SrTiO3 and PbTiO3/SrTiO3. The density of state （DOS） and electronic charge profiles show that there are strong hybridizations between atoms Ti and O and between atoms Pb and O which play very important roles in producing the ferroelectricities of superlattices BaTiO3/SrTiO3 and PbTiO3/SrTiO3. Ow- ing to the decline of internal electric field in SrTiO3 （ST） layer, the tetragonality and polarizations of superlattices decrease with increasing the fraction of SrTiO3 in the superlattices. We find that the polarization of PbTiO3/SrTiO3 is largerthan that of BaTiO3/SrTiO3 at the same ratio of components, because the polarization mismatch between PbTiO3 and SrTiO3 is larger than that between BaTiO3 and SrTiO3. The polarization and tetragonality are en- hanced with respect to those of bulk tetragonal BaTiO3 in the superlattices BaTiO3/SrTiO3, while the polarization and tetragonality are reduced with respect to those of bulk tetragonal PbTiO3 in superlattices PbTiO3/SrTiO3.     

Li2K(IO3)3与Li2NH4(IO3)3的晶体结构

本文用X射线粉末法测定了Li₂K(IO₃)₃与Li₂NH₄(IO₃)₃的晶体结构和原子参数。发现Li₃K(IO₃)₃,Li₂NH₄(IO₃)₃与Li₂Rb(IO₃)₃同晶型,属单斜晶系,空间群为P2₁/α,每个单胞含有四个化合式量。室温的点阵常数分别为α=11.198?,b=11.046?,c=8.254?,β=111.53°,及α=11.327?,b=11.078?,c=8.341?,β=111.87°。讨论了二元化合物的形成与离子半径的关系。 关键词：     

Low temperature far IR spectra of (CH34)N NiCl3, (CH3)4N NiBr3 and (CD3)4N NiBr3

The known phase transition in (CH₃)₄N NiCl₃, at 171 K, has been characterised by far IR spectroscopy. The transition is explained as due to a formation of weak labile C-H,…, Cl hydrogen bonds at low temperatures, restricting the “free” internal rotations of the methyl groups and perhaps at the same time ordering the orientations of the tetramethylammonium ions. No similar transition in (CH₃)₄N NiBr₃ was found.     

Structure,electrical and magnetic properties of CaAs3, SrAs3, BaAs3 and EuAs3

The crystal structures and electrical properties of CaAs₃, SrAs₃, BaAs₃ and EuAs₃ have been studied by single crystal X-ray investigations, temperature dependent resistivity measurements and optical measurements. The structures of the triclinic CaAs₃ and monoclinic SrAs₃, BaAs₃ and EuAs₃ are closely related. The two-dimensional infinite polyanionic AS₃^2? nets are derivatives of the black phosphorus structure. CaAs₃ and BaAs₃ are semiconducting, while SrAs₃ and EuAs₃ show semimetallic behavior. The paramagnetic EuAs₃ undergoes a magnetic phase transition at 10.5 K.     

Heats of solution/substitution in TlNO3 and CsNO3 crystals and in RbNO3 and CsNO3 crystals from heats of transition: the complete phase diagrams of TlNO3-CsNO3 and RbNO3-CsNO3 systems

From measurements of the decrease in the heat (enthalpy) of transition in the solid phase using differential scanning calorimetry, the apparent molar heats of solution, slope ΔH_t/x, the partial molar heats of solution at infinite dilution, χ, and the heats of solution, ΔH_s^°, of Tl⁺ in CsNO₃ crystal and Cs⁺ in TlNO₃ crystal and Rb⁺ in CsNO₃ crystal and Cs⁺ in RbNO₃ crystal along with their recovered lattice energies, ΔH_L^°, are reported. ΔH_s^° of Tl⁺ and Rb⁺ in CsNO₃ crystal are each found to be negligible or zero representing an ideal solid solution, i.e. ΔH_mix=0. The complete phase diagrams of the TlNO₃-CsNO₃ and RbNO₃-CsNO₃ systems with details of the sub-solidus regions are included. The properties of Tl_(1−x)Cs_xNO₃ and Rb_(1−x)Cs_xNO₃ compositions are discussed in terms of a ‘mixed crystal’ or ‘crystalline solid solution’ in relation to parallel compositions of Tl_(1−x)Rb_xNO₃.     

Far ultraviolet reflectance spectra of CeF3, PrF3 and NdF3

Near-normal incidence reflectance measurements are carried out on thin films of CeF₃, PrF₃ and NdF₃ in the energy range of 6–40 eV. Tentative interpretations are given for different observed structures.     

A new sodium samarium borate Na3Sm2(BO3)3

A new sodium samarium borate with composition Na₃Sm₂(BO₃)₃ (NSBO) has been synthesized by high temperature solid state reaction. The yellowish transparent single crystals of Na₃Sm₂(BO₃)₃ have been grown from the Na₂CO₃-H₃BO₃ flux system using the top-seeded solution growth (TSSG) method. X-ray diffraction analysis demonstrated that the NSBO crystals belong to orthorhombic systems and lattice parameters are a=5.0585 Å, b=11.0421 Å, c=7.0316 Å. The measurement of the infrared spectrum indicated that the basic anionic groups are the BO³⁻₃ groups. Furthermore, Na₃Sm₂(BO₃)₃ exhibits an optical second harmonic generation effect which is close to that of KDP (KH₂PO₄).     

Third and fourth order elastic constants of fluoperovskites CsCdF3, TlCdF3, RbCdF3, RbCaF3

The hydrostatic dependence of the second order elastic constants of several fluoperovskites has been measured and studied from a macroscopic point of view and through a force field analysis. The first part of this paper is devoted to the experimental determination of some combinations of the third and fourth order elastic constants. The second part analyses the pressure dependence of the second order elastic constants from a macroscopic point of view. The large values of the second order anharmonicity coefficients $\text{b}{}_{\mathrm{ij}}\text{=}\text{1}\text{2}\text{(}\text{?}{}^2\text{C}{}_{\mathrm{ij}}\text{?P}{}^2\text{)}{}_0\text{C}{}^{\mathrm{(0)}}{}_{\mathrm{ij}}$ are connected to the occurrence of a phase transition in some compounds, whereas the first order coefficients $\text{(}\text{?C}{}_{\mathrm{ij}}\text{?P}\text{)}{}_0$ have an order of magnitude which agrees with a quasiharmonic hypothesis. The third part is devoted to the microscopic interpretation of the third order elastic constants. A rigid ion model is used with either classical Born Mayer potentials or a modification of these potentials with an axial term (Cowley and Rousseau's models).     

Ionic conductivity of the perovskites NaMgF3, KMgF3, KMgK3 and KZnF3 at high temperatures

We have carried out a study of the ionic conductivity of NaMgF₃, KMgF₃ and KZnF₃ up to temperatures close to the melting point. Our results, in contrast to previous reports in the literature, show no abnormal ionic conductivity at high temperatures. Care in interpretation of results is required because of surface electronic conduction.     

Microwave spectrum of (CH3)3CCN-SO3

Eight rotational transitions of the complex (CH₃)₃CCN-SO₃ have been recorded using pulsed-nozzle Fourier transform microwave spectroscopy and a series of ab initio calculations has been performed. The complex is a symmetric top with free or nearly free internal rotation of the SO₃ and (CH₃)₃CCN subunits. The nitrogen-sulfur bond distance is determined to be 2.394(19) Å. Calculations at the MP2/aug-cc-pVTZ level/basis, which are in excellent agreement with the experimental results, give a binding energy of 11.0 kcal/mol relative to (CH₃)₃CCN and SO₃. Physical properties of the system, including N-S bond length, N-S-O angle, binding energy, and the degree of electron transfer (obtained from Townes and Dailey analysis of the ¹⁴N nuclear quadrupole coupling constant) are compared with those of similar complexes. The proton affinity of the base is a useful parameter for ordering complexes in the series.     

RbIO3-HIO3和CsIO3-HIO3两个赝二元系的研究

用X射线衍射及差热分析法研究了两系统的相平衡。确定了RbH₂(IO₃)₃的结构(三斜晶系,点阵常数:a=8.338?,b=8.244?,c=8.254?,α=60.66°,β=85.58°,γ=66.01°,z=2)。密度D_m=4.61g/cm³。CsIO₃-HIO₃系中有两个化合物:CsH(IO₃)₂(为质子导体)和3CsIO₃·17HIO₂。 关键词：     

Absolute sense of pyroelectric p3 and piezoelectric d33 coefficients in 3La (IO3)3.HIO3.7H2O

The pyroelectric coefficient p₃ in 3La(IO₃)₃.HIO₃.7H₂O has an average value 2.0×10^-5 Cm^-2 in the temperature range 152 to 240 K. The resistivity decreases from 10¹² to 10¹⁰ ohm-cm between 258 and 338 K. At 298 K, the piezoelectric coefficient d₃₃  19×10^-12CN^-1. Positive polarity is generated on (001) by increasing temperature or tensile stress. A displacement toward (001) by La³⁺ or H₃O⁺ ions of 1×10^-4 Å per K or 10⁶Nm^-2, or rotation of the water molecule or iodate ion dipoles by about 5 arc minutes per K or 10⁶Nm^-2, produces the observed polarity.     

Photoelectron spectra of As4S3, P4S3, P4Se3 and As4O6

The He(I) UV photoelectron spectra of As₄S₃, P₄S₃, P₄Se₃ and As₄O₆ are reported in this paper. The spectra of As₄S₃ and the isostructural molecules P₄S₃ and P₄Se₃ comprise seven broad but clearly defined peaks, whilst the spectrum of As₄O₆ consists of six peaks and two shoulders. By comparing the spectra with one another and with the photoelectron spectra of other arsenic and phosphorus compounds, the character and symmetry species of the highest-energy occupied molecular orbitals of the molecules have been assigned.     

La0.67Ca0.33MnO3薄膜皮秒光电效应

在1064 nm波长脉冲激光（脉宽25 ps）的照射下，钙钛矿氧化物薄膜La0.67Ca0.33MnO3/SrTiO3具有超快光电效应，对激光脉冲显示ps量级的响应时间，上升沿响应时间300 ps，半高宽700 ps，同时，对激光能量的响应灵敏度为500 mV/mJ。     

Surface polaritons in KTaO3 and SrTiO3

The upper two surface polariton dispersion branches of KTaO₃ and SrTiO₃ were measured by attenuated total reflection and compared to calculated curves based on data for the dielectric function which were derived from a Kramers-Kronig analysis of reflectivity spectra. In KTaO₃ we observe a splitting of the highest branch caused by a strong combination band. The nature of that band is discussed qualitatively.     

Tm3+ 掺杂ZrF4 -BaF2 -LaF3 -AlF3 -NaF-PbF2玻璃激光制冷中荧光再吸收效应的理论分析

固体材料的激光制冷是近年来发展起来的一个新的研究领域. 掺Tm³⁺的ZrF₄-BaF₂-LaF₃-AlF₃-NaF-PbF₂(ZBLANP)玻璃材料是激光冷却的典型材料之一. 与另一种制冷掺杂离子Yb³⁺相比,Tm³⁺具有更好的制冷潜力. 目前制约材料制冷的一个主要机理就是荧光再吸收. 首先根据Tm³⁺:ZBLANP的光谱参数,利用半经典的随机行走模型得到了不同情况下的平均荧光再吸收次数,随后分析了荧光光子界面出射的全反射效应,并对所得结果进行了修正. 计算结果表明,荧光再吸收会导致量子效率降低0.5%-1%,出射荧光波长红移达到2-10 nm,激光制冷的效率和功率降低. 为了有利于荧光出射和净制冷的实现, 宜采用小体积细长棒的制冷元. 关键词： 激光制冷 稀土离子 荧光再吸收     

Magnetic susceptibility of NbSe3 and TaSe3

The magnetic susceptibility of NbSe₃ shows a decrease beginning slightly above its upper charge density wave transition (CDW) of 144 K, but no change within our resolution near the 59 K transition. The change in the density of states at the Fermi level due to the upper transition is 0.14 states-eV/Nb. TaSe₃ on the other hand has a temperature independent susceptibility. In some cases the trichalcogenides are contaminated with their corresponding dichalcogenide. Such contamination can be observed by susceptibility measurements in the case of 2HTaSe₂ but not of 2HNbSe₂. We also report an anomaly in the susceptibility of 4HaNbSe₂, which suggests a CDW transition at 45 K.