LaNbO4晶体的弹性系数和声速的计算

利用群论方法,对LaNbO₄晶体,建立了计算弹性系数的一般公式和由弹性系数反演力常数的解析式。在4个近邻力常数的近似下,计算了LaNbO₄晶体各种弹性波的传播速度。 关键词：     

Elastic and photoelastic constants of NaCl,KBr and LiF by Brillouin scattering

Elastic and photoelastic constants of NaCl, KBr and LiF were determined from Brillouin frequency shifts and intensities. Reported differences between the hypersonic and ultrasonic elastic constants for KBr and LiF were not confirmed. For each material the constants were in good agreement with the ultrasonic values. Scattering from longitudinal, transverse and mixed phonon modes was clearly observed for each material.     

Electrical conductance time constants for freely decaying arcs

Electrical conductance time constants for the early stages of free decay after current modulation have been calculated from experimental measurements on a 5 mm diameter cascade arc at atmospheric pressure. The time constants were found by measuring the electric field response of the asymptotic portion of the arc column immediately after a sudden step decrease of arc current. The electric field strength was monitored by means of the copper cooling disks of the cascade, whose probe characteristics were studied thoroughly. The initial high current was supplied by a capacitor discharge circuit which was inductively compensated to produce a square wave pulse of ～ 2 msec duration. Time constants for initial decay were measured in both argon and nitrogen for initial currents ranging from 100 to 400 amperes. The initial free decay time constants of nitrogen were found to increase weakly from approximately 25 to 35 usec over the initial current range considered. The time constants of argon decreased from approximately 100 to 60 Μsec over the same initial current range.     

Optical constants of titanium and silicon dioxide films

In this paper a study of optical constants of titanium and silicon dioxide films prepared in Balzers BAK 600 and BA 510 conventional high-vacuum apparatus is described. Both the dispersion and the geometrical thickness were determined from normal reflectance spectrum by adapted general algorithm of the statistical interpretation of measured data. The dependence of optical constants on oxygen pressure for both materials and the evaporation rate dependence for titanium dioxide were obtained. The time changes of these constants were also measured.     

Accurate measurements of small J coupling constants under inhomogeneous fields via intermolecular multiple-quantum coherences

Two new NMR pulse sequences, based on intermolecular multiple-quantum coherences (iMQCs), were developed to obtain apparent J coupling constants with a scaling factor from one to infinity relative to the conventional J coupling constants. Here the apparent J coupling constants were defined as apparent peak separations in unit of Hz in a reconstructed spectrum for a coupled spin system. Except for the adjustable scaling factor for apparent J coupling constants, the sequences hold the advantage of high acquisition efficiency, and retain the spectral information such as chemical shifts, multiplet patterns, and relative peak areas under inhomogeneous fields. For spin systems with small scalar coupling constants, well-resolved J-spectra can be achieved by selecting a proper scaling factor. Theoretical predictions are in good agreement with simulation results and experimental observations.     

Spectra of the <Emphasis Type="Italic">gauche</Emphasis>-conformer of isopropyl alcohol in the millimeter and submillimeter wavelength regions

The spectrum of isopropyl alcohol in the millimeter region was recorded using a hybrid radio-spectrometer. A total of 1278 rotational and vibration-rotational transitions of its gauche-conformer were identified. Rotational constants and quartic centrifugal constants were refined. Sextic centrifugal constants and all six internal rotation constants were determined. The tunnel splitting parameter was refined. The reduced Hamiltonian of internal rotation is used for the first time in full format and describes sufficiently well the vibration-rotational spectrum of the gauche-conformer of isopropyl alcohol, which is complicated by internal rotation. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 5, pp. 659–665, September–October, 2008.     

Analysis of ν2 of H2Se

The infrared absorption spectrum of ν₂ of H₂Se in the region from 885 to 1347 cm^?1 was obtained with a resolution limit of 0.025 cm^?1 on the University of Denver 50-cm FTIR spectrometer system. We have assigned 1604 lines for the six isotopomers of H₂Se, including 25 lines for the H₂⁷⁴Se isotopomer, and have analyzed them using Watson's A-reduced Hamiltonian in the I^r rotational representation. Ground state constants for each of the five most abundant isotopomers were obtained from fits of microwave transitions combined with weighted averaged ground state combination differences formed from the infrared bands (010), (020), (100), and (001). Upper state constants for each of the five most abundant isotopomers were obtained from least-squares fits of the spectral lines of ν₂, keeping the ground state constants fixed to the values determined from our ground state fits. An alternate set of ground state constants together with isotopic mass adjustment constants for all six isotopomers was determined by simultaneously fitting all available microwave transitions and infrared ground state combination differences. Keeping this set of ground state constants fixed, a single set of upper state constants and isotopic mass adjustment constants for the ν₂ band was determined by a simultaneous fit of infrared spectral lines from all six isotopomers.     

Lattice dynamics of ZnO

Some phonon dispersion curves in ZnO have been determined by inelastic neutron scattering. Shell model calculations with 10 parameters were fitted to the neutron data, to optical frequencies and to dielectric constants. Good agreement was obtained including some elastic constants which were calculated from the model.     

溅射条件对ZnS薄膜的光学常量和微结构的影响

为了研究制备条件对射频溅射ZnS薄膜光学常量和微结构的影响,在浮法玻璃上制备了不同溅射气压、溅射功率和溅射温度的ZnS薄膜,利用紫外可见近红外分光光度计在300～2 500 nm的波长范围内测量了薄膜的透射和反射光谱,并通过光谱拟和计算出ZnS薄膜的光学常量以及禁带宽度.通过X射线衍射分析了薄膜的微结构随溅射温度的改变.研究结果表明,随着制备条件的不同,ZnS薄膜的光学常量和微结构会发生变化.     

具有六方晶系结构的多晶体材料弹性常数——Y弹性常数

利用最近提出的新的物理参量——Ｙ弹性常数,将其应用于具有六方晶系结构的多晶体材料.推导了六方晶系结构的多晶体材料之Ｙ弹性常数,通过算例与具有六方晶系结构的多晶体材料之X射线弹性常数进行了比较.运用这个Ｙ弹性常数进一步推导出的多晶体材料整体之机械弹性常数的表达式与Kneer的研究结果中的表达式虽然形式不同,但针对具体材料所计算的结果却完全符合. 关键词： Y弹性常数 六方晶系 多晶体材料     

The harmonic force fields of methylene chloride and dichlorosilane from combined microwave and infrared data

The harmonic force fields of methylene chloride and dichlorosilane have been obtained by combining the vibrational wavenumbers and centrifugal distortion constants of several isotopic species. Although enough data were available from earlier work for dichlorosilane, it was first necessary for methylene chloride to determine its distortion constants from microwave spectra. Transitions were measured up to J = 80 and J = 90 for CH₂Cl₂ and CD₂Cl₂, respectively, and the analysis gave accurate rotational constants, and quartic and sextic distortion constants. Ground-state effective, substitution, ground-state average and approximate equilibrium structures have been obtained for both molecules.     

Ab initio studies of the structural,elastic, electronic and thermal properties of NiTi2 intermetallic

First principles calculations were performed in the framework of the density functional theory (DFT) using the Full Potential–Linear Augment Plane Wave method (FP–LAPW) within the generalized gradient approximation (GGA) to predict the structural, electronic, elastic and thermal properties of NiTi₂ intermetallic compound. By using the Wien2k all-electron code, calculations of the ground state and electronic properties such as lattice constants, bulk modulus, presure derivative of bulk modulus, total energies and density of states were also included. The elastic constants and mechanical properties such as Poisson’s ratio, Young’s modulus and shear modulus are estimated from the calculated elastic constants of the single crystal. Through the quasi-harmonic Debye model, the preasure and temperature dependences of the linear expansion coefficient, bulk modulus and heat capacity have been investigated. Finally, the Debye temperature has been estimated from the average sound velocity according to the predicted polycrystal bulk properties and from the single crystal elastic constants.     

The far-infrared rotational spectrum of nitrous acid (HONO) and its deuterated species (DONO) studied by high-resolution Fourier-transform spectroscopy

In this paper, we present the first high-resolution (0.003 cm⁻¹) absorption measurements of the pure rotational spectra of nitrous acid (trans- and cis-HONO) and its deuterated species (trans- and cis-DONO) in the far-infrared region between 40 and 150 cm⁻¹. The spectra were first assigned based on rotational constants from previous studies in the microwave and mid-infrared regions. New rotational and centrifugal distortion constants were determined for all four species. The accuracy of the principal rotational constants was improved, and several quartic and sextic (and even a few octic) centrifugal distortion constants were obtained for the first time. Synthetic spectra calculated using the new constants of this study reproduce the observed spectra very well.     

Centrifugal Distortion Analysis of a Near-Spherical Top, SO(2)F(2): The First Determination of All Six Quartic Centrifugal Distortion Constants for an Asymmetric Top

The rotational spectrum of the near-spherical top molecule SO(2)F(2) (sulfuryl fluoride) has been investigated by microwave Fourier transform spectroscopy and by millimeter-wave spectroscopy. The ground state spectrum has been measured from 10 to 472 GHz. One of the reasons for studying this molecule is that it is a nearly spherical top and we wanted to verify our theoretical prediction that for such a molecule all six quartic centrifugal distortion constants (and nine sextic distortion constants) should be determinable, while for a standard asymmetric rotor, Watson has shown that only five quartic and seven sextic distortion constants are determinable. The analysis of the spectra confirmed our predictions, because all six quartic constants were well determinable. The results have been confirmed independently by ab initio calculations of the force field and quartic distortion constants. Because the molecule is relatively heavy, contributions of some sextic constants are too small and we have not been able to determine all nine sextic constants predicted by theory. Copyright 2000 Academic Press.     

Optische Konstanten aufgedampfter Eisenschichten

Iron was heated and evaporated by electron bombardment. The condensation upon glass plates gives layers with highly reproducible thicknesses and optical constants. In the range of the visible spectrum, the constants were determined for opaque layers (thickness≧1000 Å) by the elliptical analysis of reflected light. They vary reproducibly with the conditions of preparation. The range of values covers most of the measurements published to date for iron. For oblique condensed layers the optical constants are very strongly anisotropic. Irreversible changes of the constants within the range of temperature from 150 to 400° C are presumably connected with crystalline growth.     

取代喹啉杂环碱在水中质子化作用平衡常数的测定

前文我们对取代吡啶杂环碱在水中质子化作用平衡常数进行了测定^[1]。本文利用和前文相同的方法测定了具有不同取代基喹啉碱类的平衡常数^[2]。发现如果喹啉某位的氢被吸电子基团取代,则喹啉碱的平衡常数减小,而被给电子基团取代,则喹啉碱的平衡常数增大。这样对探讨这些基团的电子效应是有实际意义的。     

Measurement of lifetimes and collisional rate constants for 3p levels in neon I,II and IV

Lifetimes and collisional quenching rate constants have been measured for 3p levels in Ne I, Ne II, and Ne IV. The levels were populated by direct excitation from the neon ground state using a pulsed beam of 100 MeV³²S ions from the Munich Tandem van de Graaff accelerator. Beam pulses were 2 ns long (FWHM) and had a repetition rate of 78 kHz. Lifetimes were measured by time resolved optical spectroscopy. Collisional rate constants were determined from time spectra for various target gas pressures.     

Application of the method of energy moments to an analysis of the rotational and centrifugal constants of the H2O molecule

A method is described to compute the centrifugal constants from the first and second order energy moments. Presented as an illustration is a computation of the centrifugal constants of the H₂O molecule for the 000 vibrational state; conditions proposed in [2] were imposed on the parameters of the unitary transformation; the centrifugal constants obtained under such conditions reproduce the spectrum to 0.1 cm^–1 accuracy.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 80–84, August, 1973.     

Critical properties of non-spherical molecule fluids from virial expansion

For systems of Kihara molecules with circular cores, the values of the reduced critical constants were determined from the fourth-order virial expansion as functions of the core diameter/thickness ratio. From expressions for the reduced functions both for the oblate and prolate shapes, the values of critical constants of four cyclic hydrocarbons and four branched alkanes were evaluated and compared with the experimental data and values obtained from the perturbation theory.     

Electronic effect of ionic‐pair substituents

For conventional organic substituents, an almost linear relationship can be established between the para Hammett constants in aqueous solutions and chemical shifts or natural population analysis charges (NPA charges). Based on these correlations, the Hammett constants of six synthesized ionic‐pair substituents were estimated via the chemical shifts, which were well in agreement with the results calculated by NPA charges. The para Hammett constants of 89 different ionic‐pair substituents (77 anion‐cationic and 12 cation‐anionic) were therefore calculated in the gas phase based on the density functional theory method. The results show that both the anion‐cationic and cation‐anionic substituents are electron‐withdrawing groups and the different cation–anion combinations could tune the Hammett constants of the ionic‐pair substituents in a range from 0.03 to 0.77. Copyright © 2013 John Wiley & Sons, Ltd.