X-ray diffraction in a crystal with a linear lattice parameter variation

The dynamical X-ray diffraction in a crystal with a linear lattice parameter variation (LLPV) and its applications to the X-ray diffractional investigations of thin solid state films are studied. For the interpretation of the reflection coefficients angular dependence is the Fresnel layers construction developed. Some particular cases of the general diffractional problem solutions for the crystals with LLPV are treated.     

X-ray diffraction radiation from an oscillator in a crystal (Baryshevsky-Dubovskaya effect)

It is shown that the diffraction of X-rays being produced by an oscillator (Baryshevsky-Dubovskaya effect) leads to excitation of additional branches in the oscillator radiation spectrum within a wide angular interval and to the formation of an opacity area for the radiation.     

X-ray diffraction analysis of the surface acoustic wave propagation in langatate crystal

X-ray diffraction on a langatate crystal (La₃Ga_5.5Ta_0.5O₁₄, LGT) modulated by a Λ=12 μm Rayleigh surface acoustic wave (SAW) was studied in a double axis X-ray diffractometer scheme at the BESSY synchrotron radiation source. SAW propagation in the crystal causes sinusoidal modulation of the crystal lattice and the appearance of diffraction satellites on the rocking curves, with their number, angular positions, and intensities depending on the wavelength and amplitude of acoustic vibrations of the crystal lattice. Strong absorption of X-ray radiation in LGT enables the observation of the diffraction spectra extinction at certain SAW amplitudes. X-ray diffraction spectra analysis makes it possible to determine SAW amplitudes and wavelengths, to measure the power flow angles, and investigate the diffraction divergence in acoustic beam in LGT.     

Temperature factor of X-ray diffraction and diffuse scattering from helical polymer crystal

A theoretical treatment for the effect of thermal vibration on the X-ray scattering intensity for a helical polymer crystal is presented. The treatment involves assumptions that (1) the unit cell of the crystal contains only one polymer chain and (2) fluctuations of the atomic positions are small. The temperature factor of the intensity of Bragg reflections is expressed in terms of mean squares of fluctuations of helical parameters. The diffuse scattering is also considered in a special case.     

Evidence by X-ray diffraction for hexatic B and crystal B structures in a pure compound

This letter presents an X-ray experiment which provides direct evidence of the existence in a pure compound of both B modifications, namely the crystal B and the hexatic B phases.In the hexatic B phase a hexagonal 1 0 0 diffuse peak was observed for which a satisfactory fit was obtained by assuming an in-plane structure factor of Lorentzian shape in agreement with theoretical predictions, leading to an in-plane positional correlation length $\text{ξ}{}_{\mathrm{\mid }}\text{= 60 ± 6}\text{A}\text{?}$.     

Feature of kinematic diffraction of nonmonochromatic divergent X-ray beams in a crystal with a periodically strained lattice

Coherent scattering of a nonmonochromatic divergent beam of X-ray quanta in a crystal excited by an acoustic wave is described using a kinematic approach. The possibility of manifestation of a peculiar effect of amplification of the diffracted X-ray beam by the acoustic wave is predicted using this approach.     

利用高分辨X射线衍射研究磷酸二氢钾晶体晶格应变应力

采用高分辨X射线衍射技术对大尺寸磷酸二氢钾(KDP)晶体的晶格应变进行了测量,并定量分析了其晶格应力.探讨出KDP晶体容易沿着[001]方向发生开裂,与实际工作中的开裂现象相符合;进一步归纳总结了晶体生长过程中引入内应力而导致晶体开裂的主要因素.研究结果为提出相应的晶体防裂措施提供了重要的理论基础.     

Failure analysis of magnets in a servomotor by Mössbauer and X-ray diffraction

The failure of a servo motor with Nd–Fe–B magnets under harsh atmospheric conditions is analysed. The magnets presented corrosion both on the side glued to the rotor (magnet-bottom) and on the opposite side (magnet-top), and eventually came off the rotor shaft. The corrosion products were studied by X-ray diffraction and Mössbauer spectroscopy and compared to the uncorroded magnet material. The observed products, Nd(OH)₃ and iron oxyhydroxides, evolve from the magnet-bottom to the top, and show that the atmospheric environment was wet with a high concentration of salts. Finally, some paramagnetic powder was found away from the magnet set, as a consequence of rotor rotation, and it represents a further oxidation process of the magnet products. The surface protection of the magnets has shown to be insufficient for the atmospheric working conditions.     

Structure and dynamics of clean and adsorbate-covered crystal surfaces studied by surface X-ray diffraction

Received: 24 March 1998/Accepted: 21 August 1998     

Polymorphism and chevron layer structure of an antiferroelectric liquid crystal studied by X-ray diffraction

We report X-ray diffraction experiments performed on an antiferroelectric compound exhibiting a very rich polymorphism (). The structural study of the unknown phases only allows us to exclude some phenomenological models. The use of oriented planar samples prepared between solid glass plates generate by cooling from the phase a chevron structure of tilted layers already well characterized for the phase. The extensive analysis of the evolution of the chevron structure through the numerous smectic-smectic phase transitions provides some original information in three distinct areas: fundamental data on the important physical parameters in the chevron structure formation, detection of the smectic-smectic phases transition by small change of the chevron structure, and information on the local molecular order induced by the alignment layer (interaction with a rubbed polymer). Received: 13 November 1996 / Received in final form: 19 January 1997 / Accepted: 30 January 1998     

X-ray diffraction analysis of double-layer systems irradiated by a high-power ion beam

Systems of thin Ni films on a copper substrate, thin Ni films on an aluminum substrate, and St20 steel covered with graphite irradiated by a high-power ion beam of nanosecond duration have been investigated by x-ray diffractometry. The mixing of nickel with aluminum and St20 steel with graphite is revealed. It is shown that the mixing predominantly occurs in the liquid phase and depends on the thermal properties of a film and substrate.     

Standardless analysis of solids by mass spectrometry with inductively coupled plasma

The possibility of the standardless mass spectrometric analysis of the elemental composition of solids has been discussed. The effect of each stage of the laser plasma expansion on the formation of the coefficient of relative sensitivity of elements in the sample has been studied theoretically and experimentally. It has been shown that the stages of ionization and detection make the main contribution to the formation of the coefficient of relative sensitivity. It has been proposed to separate dissociation and ionization processes in time and/or in space. To compensate for the energy spread of ions at the output of the analyzer, a circuit has been proposed for aligning the energy of ions before their detection.     

Study by X-ray diffraction and Raman spectroscopy of a Dy@C $_{\mathsf{82}}$ single crystal

We report the first X-ray diffraction and Raman spectroscopy study of a single crystal of the rare-earth endohedral fullerene Dy@C₈₂. The lattice is found to be body-centered cubic (a = 25.79 Å, space group which is at variance with previous reports and confirms that several types of structures can be stabilized in Dy@C₈₂. X-ray diffraction/diffuse scattering methods reveal no low-temperature change down to 12 K for the present structure. The Raman spectroscopy data are comparable to those of other M@C₈₂ endohedral compounds. However, the Dy oxidation state and the force constant of the low-frequency metal-cage stretching mode do not follow the simple relationship observed before.Received: 29 August 2003, Published online: 15 October 2003PACS: 61.10.Nz X-ray diffraction - 61.48.+c Fullerenes and fullerene-related materials - 78.30.Na Fullerenes and related materialsT. Wågberg: Present address: Groupe de Dynamique des Phases Condensées, Université Montpellier II, Place E. Bataillon, CC026, 34095 Montpellier, France     

Depolarization of a neutron beam in Laue diffraction by a noncentrosymmetric crystal

The depolarization of a neutron beam executing Laue diffraction in a thick (～3.5 cm) noncentrosymmetric α-quartz crystal is observed. This effect was predicted by us earlier and suggested for measuring the electric dipole moment (EDM) of a neutron. The effect is due to an interaction of the magnetic moment of a moving neutron with a strong crystal electric field, as a result of which the neutron spin rotates in opposite directions for waves of two types excited in the crystal. The effect is studied for neutron diffraction by a system of crystallographic (110) planes at Bragg angles close to π/2, up to 87°. It is shown that, for a crystal of thickness L=3.5 cm, a direct beam initially polarized along the reciprocal lattice vector becomes depolarized upon diffraction, irrespective of the value of Bragg angle, whereas the beam polarized perpendicular to the diffraction plane retains its polarization. The Eτ value determining the sensitivity of the method to EDM is experimentally estimated.     

Autoholography and possibility of direct phase measurement in X-ray diffraction analysis

A method for direct experimental measurement of phases of scattered waves in X-ray diffraction analysis has been proposed. To determine these phases, an unconventional holographic exposure technique (hereinafter, “autoholography”) is used, wherein a beam scattering on an object completely identical to the one being investigated, but spatially shifted and rotated in a certain manner relative to the latter, is used as a reference beam. In principle, autoholography method does not require a very high coherence of the radiation beams used since the reference beam allows to compensate for its absence to a certain extent in this case. Therefore, X-ray radiation used for X-ray diffraction analysis is also perfectly suitable for the autoholography.     

Determination and analysis of opiates in complex mixtures by surface-ionization mass spectrometry

The results of studies of the analytical opportunities of surface-ionization mass spectrometry (SIMS) for high-sensitivity and selective detection and analysis of opiate mixtures—natural opium, crude heroin, and narcotic analgesic omnopon—are presented. The experiments were carried out using an MX-1320 chemical mass spectrometer modernized for studying surface ionization (SI). It was ascertained that the opiate mixtures are ionized by highly efficient surface ionization. The bands of M⁺ (for papaverine), (M-H)⁺, (M-H-2nH)⁺, (M-R)⁺, and (M-R-2nH)⁺ ions, where M is a molecule, H is a hydrogen atom, R is a radical, are observed in the mass spectra; they are the sum of the SI mass spectra of components of the mixtures. The series of bands of ions with m/z of 144 and 146 that is characteristic of SI-morphinelike molecules is the main one in the mass spectrum of crude heroin, while for omnopon and natural opium this series is the main at low temperatures of a thermionic emitter (up to ∼900 K). At high temperatures of the thermionic emitter, the band series with m/z of 218 and 220 is the main series. Studies of natural opium, crude heroin, and omnopon have shown that the SIMS method allows analyzing mixtures without preliminary chromatographic separation thereof. The study also contains the results of comparative analyses of opiate mixtures by SIMS and chromate- and mass spectrometry (HP-6890) with electronic ionization.     

X-ray diffraction analysis and occurrence of multiple phases in Bi-Sr-Ca-Cu-O superconductors

Starting composition 1112 for Bi-Sr-Ca-Cu-oxide yields multiphase super-conductors with the proportion of constituent phases depending sensitively on the annealing temperature. The R-T curves show zero resistivity and the transition corresponding toT _c = 80 K phase prominently. However, indexing of X-ray diffraction peaks reveals presence of 80 K (lowT _c) as well as 108 K (highT _c) phase. The lowT _c phase thus corresponds to the orthorhombic structure with a unit cell ofa = 5.4Å,b = 27 Å andc = 30.56 Å. This is further understood to be composed of a pseudotetragonal cell ofa =b = 5.41 Å. The highT _c phase similarly pertains to the orthorhombic structure withc = 36 Å.     

X-ray diffraction studies of intercalation compounds prepared from aniline salts and montmorillonite by a mechanochemical processing

Inorganic-organic intercalation compounds comprised of montmorillonite (MMT) and aniline salts with different counter anions were prepared by a mechanochemical processing. The intercalation process and the formed structure of intercalation compounds were investigated via X-ray diffraction analysis. The amounts of intercalated species were very likely dependent on the types of counter anions and increased with decreasing the size of counter anions during the mechanochemical processing. Very interestingly, much larger interlayer expansions of 1.51 nm was observed for aniline hydrofluoride AnF- and aniline hydrochloride AnCl-MMT systems in higher intercalates loading levels, suggesting that neutral guest molecules also introduce within the interlayer regions together with anilinium cations by van der Waals interactions. Judging from the larger interlayer expansions and the size of guest molecules, intercalated species are expected to prefer a tri-molecular layer arrangement with their aromatic rings perpendicular to the silicate sheets. In contrast, for aniline hydrobromide AnBr-MMT, the interlayer expansion was ca. 0.52 nm, which reveals that only anilinium cations are introduced by ion exchange and they probably adopt a vertical orientation in the interlayers. It is inferred that aniline hydroiodide AnI-MMT compounds have a heterogeneous structure containing both anilinium and sodium cations in the interlayers. Different intercalation behaviors during the mechanochemical processing strongly suggest the smaller the size of counter anions, the more guest molecules can be intercalated into the confined clay interlayers in highly ordered arrangements.     

Collinear diffraction of a divergent light beam by ultrasound in a paratellurite crystal

The collinear acousto-optical interaction of a divergent light beam with ultrasound along the approximate [110] direction in a TeO₂ paratellurite crystal is investigated theoretically and experimentally. The collinear diffraction is studied at an ultrasonic frequency f ≈ 149 MHz under exposure of the crystal to an uncollimated laser light beam at a wavelength λ = 633 nm and at an angle of divergence as large as 4°. It is shown that the collinear diffraction along the direction forbidden for acousto-optical interactions of plane waves occurs only under conditions where the light beam is uncollimated and the diffraction efficiency increases with an increase in the divergence of the light beam. It is proved that the attenuation of an acoustic wave brings about a decrease in the diffraction efficiency and an increase in the transmission bandwidth of the device used. A model of the collinear acousto-optical filter based on a paratellurite crystal with an interaction length l = 2.7 cm is analyzed. The collinear acousto-optical filter is characterized by a high resolving power (～3000), a high diffraction efficiency (I₁/I₀ ≈ 0.8), and a large angular aperture (Δ? ≈ 4°). This makes collinear diffraction promising for use in acousto-optical filters based on paratellurite crystals.