共查询到20条相似文献,搜索用时 31 毫秒
1.
I. Kh. Abdukadyrova 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2012,6(1):79-85
A spectroscopic study of the effect of neutron radiation on the lattice dynamics of different cut crystalline and glassy quartz
(SiO2) has been performed. The IR spectroscopy method is used to determine the mechanisms by which the spectral characteristics
of deformation and valence vibrations vary by radiation-induced alteration of the lattices in two types of modified quartz
(α-SiO2 and ν-SiO2) as a function of the neutron fluence at low and high frequencies. It has been established that nonlinear changes in the
dose dependences between the spectral characteristics of the fundamental modes occur in two types of crystals, with different
orientations, and in glass, and the features of the spectrum modifications exist near 300–550 and 700–1400 cm−1 and at higher frequencies. The derived dose dependences are compared to those of the degenerate vibration parameters in ν-SiO2, and the extreme kinetics of the force coefficients is determined. A conclusion is made that the accumulation of radiation
damages, changes in the force field around the bridge bonds, and the phase states of SiO2 affect the observed specific behavior of the radiation-modified spectral and force parameters of the degenerate and deformation
modes in quartz samples of different types. 相似文献
2.
I. Kh. Abdukadyrova 《Journal of Applied Spectroscopy》2005,72(6):848-852
The IR-radiation reflectance spectra of α-SiO2 single crystals exposed, in a reactor, to fast neutrons with fluences changing in a wide range have been investigated. The
regularities of the change in spectral characteristics of the antisymmetric and degenerate vibrations of the bridge bonds
of the crystals studied and in the dynamic parameters of these crystals in the process of their irradiation have been determined.
The critical dynamics of the crystal lattice in the region of antisymmetric stretching and degenerate modes and the extremum
radiation kinetics of the ion-polarizability parameters and the force constants of the indicated crystals were detected. The
changes in some characteristics of these crystals, arising on their irradiation as a result of the damage of the substance,
the rupture and extension of some silicon—oxygen bonds, and the transformation of the structure of α-SiO2 single crystals by two mechanisms, have been considered.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 6, pp. 773–777, November–December, 2005. 相似文献
3.
Quasi-line low-temperature (T = 77 and 4.2 K) luminescence spectra of uranyl sulfates and oxalates have been recorded and
analyzed. It has been shown that the spectral structure is determined by the manifestation of the internal and external vibrations
of both the uranyl ion and molecular groups (SO4)2– and (C2O4)2–bonded to the uranyl ion. The spectral line half-width is of the order of ≈5–7 cm–1; the line shape, close to Lorentzian. The fluorescence spectra may be complicated by structural defects in the crystals. 相似文献
4.
Nobumitsu Sakai Masato Takakura Harutoshi Imamura Miki Sugimoto Yasuto Matsui Hirokazu Miyoshi Aki Nakayama Minoru Yoneda 《Journal of nanoparticle research》2012,14(5):849
We analyzed the whole-body distribution of 14C–ADP-labeled silica nanoparticles (14C–ADP–SiO2 nanoparticles) and submicron particles (14C–ADP–SiO2 submicron particles) after intravenous injection into ICR mice. The 14C–ADP–SiO2 nanoparticles and submicron particles were synthesized before the injection and the particle size was 19.6 and 130 nm, respectively.
Similarly, the shape was spherical and the crystallinity was amorphous. After the synthesis, we injected mice with the 14C–ADP–SiO2 nanoparticles or the 14C–ADP–SiO2 submicron particles and dissected tissues after 1, 2, 4, 8 and 24 h. The radioactivity in the tissues was measured with a
liquid scintillation counter. As a result, the retention percentage in bone, skin, lymph nodes, and the digestive mixture
was at least twofold higher in the 14C–ADP–SiO2 nanoparticles-exposed mice, whereas the retention percentage in the kidney was statistically higher in the 14C–ADP–SiO2 submicron particles-exposed mice. Both types of 14C–ADP–SiO2 particles mainly translocated to the muscle, bone, skin, and liver, but hardly translocated to the brain and olfactory bulb.
Furthermore, the 14C–ADP–SiO2 nanoparticles had a higher retention percentage (62.4 %) in the entire body at 24-h post-injection than did the 14C–ADP–SiO2 submicron particles (50.7 %). Therefore, we suggested that the 14C–ADP–SiO2 nanoparticles might be more likely than the 14C–ADP–SiO2 submicron particles to be retained in the body, and consequently they might be gradually accumulated by chronic exposure. 相似文献
5.
I. N. Ogorodnikov A. V. Porotnikov A. V. Kruzhalov V. Yu. Yakovlev 《Physics of the Solid State》1998,40(11):1817-1822
A study of recombination kinetics in LiB3O5 (LBO) crystals by time-resolved luminescence and absorption spectroscopy is reported. An investigation of the kinetics of
transient optical absorption (TOA) and luminescence under ns-scale electron-beam excitation performed within a broad temperature
range of 77–500 K and a 1.2–5-eV spectral interval has established that the specific features in the recombination kinetics
observed in LBO involve electronic, B2+, and hole, O−, trapping centers. The TOA and luminescence kinetics, as well as their temperature dependence, are interpreted by a model
of competing hole centers. Relations connecting the kinetics parameters and the temperature dependence to the parameters of
the main LBO point defects are presented.
Fiz. Tverd. Tela (St. Petersburg) 40, 2008–2014 (November 1998) 相似文献
6.
I. Kh. Abdukadyrova 《Journal of Applied Spectroscopy》2006,73(4):557-561
IR spectroscopy has been used to study the process of structural damage and changes in some characteristics of fused silica
irradiated by fast neutrons over a very broad fluence range (1017–1021 cm−2). Features of the change in spectral characteristics of the bending and stretching vibrations of the bridge bonds have been
identified, and also a comparative analysis has been carried out with radiation-induced changes in a series of optical spectra
in the UV and visible regions, and structural parameters and other characteristics of wafers irradiated by different fluences.
A correspondence has been established between the features of the radiation-induced changes in the optical, luminescence,
and structural properties, and extremal points have been observed on the dose dependences. Based on the results obtained,
a mechanism of radiation-induced rearrangement of the silica structure is suggested.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 494–497, July–August, 2006. 相似文献
7.
A. N. Murashkevich A. S. Lavitskaya T. I. Barannikova I. M. Zharskii 《Journal of Applied Spectroscopy》2008,75(5):730-734
The composites xTiO2-(1−x)SiO2 (x = 0.1, 0.5, 0.9) were obtained by coprecipitation from solutions of alkoxides: tetraethoxysilane (TEOS) and titanium tetraisopropoxide
(TIPT). Intermolecular interaction of the components of the composite is apparent in the IR absorption spectra in the 928–952
cm−1 region, and is connected with bending vibrations of the Si-O-Ti bond.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 5, pp. 724–728, September–October, 2008. 相似文献
8.
9.
The methodological aspects of PSEE spectroscopy of the surface of irradiated dielectrics have been considered. A generalized
method for processing the nonselective photostimulated electron emission (PSEE) spectra taking into account the effects of
radiation electrification and structural disordering is proposed and has been substantiated. The procedure of separation of
the emission contribution of discrete radiation centers providing, in the stationary approach, estimation of a number of parameters
and the concentration of emission-active defects of the surface layer of the material has been described. The potentialities
of the method have been demonstrated with the example of Be2SiO4 phenacite crystals and crystalline and glassy SiO2. Diamagnetic oxygen-deficient centers, body and surface E'-centers, as well as hole O
1
0
-centers on nonbridging oxygen atoms have been registered.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 3, pp. 381–385, May–June, 2005. 相似文献
10.
T. V. Panchenko 《Physics of the Solid State》1997,39(7):1085-1090
Anomalies of the dielectric properties of undoped and aluminum-and gallium-doped crystals of Bi12SiO20 are investigated in the frequency and temperature range ν=102–108 Hz and T=300–800 K. They are shown to be due to Debye relaxation processes and determined by the relaxor parameters. The mechanism
of electron thermal polarization is discussed.
Fiz. Tverd. Tela (St. Petersburg) 39, 1223–1229 (July 1997) 相似文献
11.
Sonja Hermann Nils-Peter Harder Rolf Brendel Dirk Herzog Heinz Haferkamp 《Applied Physics A: Materials Science & Processing》2010,99(1):151-158
In this work, we report on laser ablation of thermally grown SiO2 layers from silicon wafer substrates, employing an 8–9 ps laser, at 1064 (IR), 532 (VIS) and 355 nm (UV) wavelengths. High-intensity
short-pulse laser radiation allows direct absorption in materials with bandgaps higher than the photon energy. However, our
experiments show that in the intensity range of our laser pulses (peak intensities of <2×1012 W/cm2) the removal of the SiO2 layer from silicon wafers does not occur by direct absorption in the SiO2 layer. Instead, we find that the layer is removed by a “lift off” mechanism, actuated by the melting and vaporisation of
the absorbing silicon substrate. Furthermore, we find that exceeding the Si melting threshold is not sufficient to remove
the SiO2 layer. A second threshold exists for breaking of the layer caused by sufficient vapour pressure. For SiO2 layer ablation, we determine layer thickness dependent minimum fluences of 0.7–1.2 J/cm2 for IR, 0.1–0.35 J/cm2 for VIS and 0.2–0.4 J/cm2 for UV wavelength. After correcting the fluences by the reflected laser power, we show that, in contrast to the melting threshold,
the threshold for breaking the layer depends on the SiO2 thickness. 相似文献
12.
L. A. Lisitsyna V. I. Korepanov A. A. Abdrakhmetova N. N. Timoshenko A. K. Dauletbekova 《Optics and Spectroscopy》2012,112(2):175-181
We have studied the spectral and kinetic characteristics of activated photo- and cathodoluminescence of LiF-O and LiF-WO3 crystals in the spectral range of 3.6–1.6 eV using methods of pulsed spectrometry with nanosecond time resolution in the
temperature range of 15–300 K and in the range of ionizing radiation dose absorbed by crystals of 102−2 × 103 Gy. 相似文献
13.
Infrared spectra of brassinolide and castasterone steroid phytohormones and their 24-epi derivatives
Absorption bands in IR spectra of brassinolide, castasterone, and their 24-epi derivatives in the frequency range 3800–1000
cm–1 have been interpreted. A number of spectral features distinguishing brassinolide from castasterone have been found. The conducted
analysis shows that the structural differences manifest themselves in IR spectra of the investigated brassinosteroids in the
region of stretching vibrations of CO–H, C=O, C–OH, C–O–C, CH3, CH2, and CH groups. The main distinctions in IR spectra of brassinolides and castasterones are due to the B ring structure. 相似文献
14.
The Raman spectra of the (GaN)129, (SiO2)86, and (GaN)54(SiO2)50 nanoparticles were calculated using the molecular dynamics method. The spectrum of (SiO2)86 had three broad bands only, whereas the Raman spectrum of (GaN)129 contained a large number of overlapping bands. The form of the Raman spectrum of (GaN)54(SiO2)50 was determined by the arrangement of the GaN and SiO2 components in it. The nanoparticle with a GaN nucleus had a continuous fairly smooth spectrum over the frequency range 0 ≤ ω ≤ 600 cm−1, whereas the spectrum of the nanoparticle with a SiO2 nucleus contained well-defined bands caused by vibrations of groups of atoms of different kinds and atoms of the same kind. 相似文献
15.
R. M. Vlasova N. V. Drichko O. O. Drozdova R. N. Lyubovskaya 《Physics of the Solid State》1997,39(8):1165-1170
The reflection spectra and optical conductivity spectra of the new organic conductor ϰ-(ET)2[Hg(SCN)2Cl] with a metal-insulator transition in the spectral regions 700–5500 and 9000–40 000 cm−1 have been studied in polarized light at 300 K. A comparisonis made between the spectra obtained and the corresponding spectra
of related isostructural conductors based on the ET molecule, and also the properties of the crystal structure of the investigated
compounds. An electronic transition between the ET molecules of the dimer (ET)
2
+
in the spectral region 700–5500 cm−1 has been identified, as have the features of the electronic-vibrational structure arising as a consequence of the interaction
of this transition with the completely symmetric intramolecular vibrations of the ET molecule. It is found that the conductor
with the stronger dimer interaction between the ET molecules has the higher the transition temperature.
Fiz. Tverd. Tela (St. Petersburg) 39, 1313–1319 (August 1997) 相似文献
16.
R. M. Vlasova O. O. Drozdova V. N. Semkin R. N. Lyubovskaya 《Physics of the Solid State》1998,40(9):1447-1450
We present here for the first time polarized reflection spectra and optical conductivity spectra of single crystals of the
newly deuterated organic conductor k-(D8-BEDT-TTF)2[Hg(SCN)2Br] at room temperature. The spectral region investigated is 700–40 000 cm−1. We examined the effect of deuteration on electronic and electron-vibrational transitions observed in the spectra. The observed
shift of the electron “dimer” transition in the infrared toward lower frequencies upon deuteration is linked with an increase
in the interaction between neighboring, mutually perpendicular dimers in the structure of the deuterated crystal. A lowering
of the symmetry of the BEDT-TTF molecule is demonstrated in crystals similar to k-(BEDT-TTF)2[Hg(SCN)2Br], relative to the symmetry D
2h
of the free molecule. We refine the assignment of the spectral features determined by the interaction of electrons with the
fully-symmetric intramolecular vibrations of the C=C, C-S, and C-C-H bonds of the BEDT-TTF molecule.
Fiz. Tverd. Tela (St. Petersburg) 40, 1595–1598 (September 1998) 相似文献
17.
Javier del-Castillo V. D. Rodríguez A. C. Yanes J. Méndez-Ramos 《Journal of nanoparticle research》2008,10(3):499-506
Undoped and Er3+-doped glass–ceramics of composition (100−x)SiO2–xSnO2, with x = 5 or 10 and with 0.4 or 0.8 mol% of Er3+ ions, were synthesised by thermal treatment of precursor sol–gel glasses. Structural studies were developed by X-Ray Diffraction.
Wide band gap SnO2 semiconductor quantum-dots embedded in the insulator SiO2 glass are obtained. The mean radius of the SnO2 nanocrystals, ranging from 2 to 3.2 nm, is comparable to the exciton Bohr radius. The luminescence properties have been analysed
as a function of sample composition and thermal treatment. The results show that Er3+ ions are partially partitioned into the nanocrystalline phase. An efficient UV excitation of the Er3+ ions by energy transfer from the SnO2 nanocrystal host is observed. The Er3+ ions located in the SnO2 nanocrystals are selectively excited by this energy transfer mechanism. On the other hand, emission from the Er3+ ions remaining in the silica glassy phase is obtained by direct excitation of these ions. 相似文献
18.
A. K. Shuaibov I. A. Grabovaya Z. T. Gomoki A. G. Kalyuzhnaya A. I. Shchedrin 《Technical Physics》2009,54(12):1819-1824
The output characteristics and parameters of the plasma of a powerful gas-discharge source of UV radiation are studied. The
UV source uses He-I2 and Xe-I2 mixtures and is excited by a longitudinal glow discharge. The pressure of the gas mixtures is varied from 100 to 1500 Pa,
and the discharge power falls into the range 15–250 W. The source (lamp) emits in the spectral interval 200–390 nm, which
covers the spectral line of the iodine atom at 206.2 nm, the spectral band of XeI(B-X) with a maximum at 253 nm, and the spectral band of with a maximum at 342 nm. For He(Xe)-I2 mixtures at a pressure of 800–1000 Pa (this pressure range is near-optimal according to our experimental data), the electron
energy distribution functions and the electron kinetic coefficients as functions of parameter E/N (E is the electric field strength, and N is the particle concentration in the discharge) are calculated. The calculated plasma parameters are used in the qualitative
analysis of key electronic processes in the plasma of an exciplex halogen UV source and will be subsequently employed in numerical
simulation of the process kinetics and output characteristics of a UV source based on helium-iodine or xenon-iodine mixtures. 相似文献
19.
N. A. Borisevich D. K. Buslov V. A. Khripach V. N. Zhabinsky 《Journal of Applied Spectroscopy》2008,75(5):637-643
Comparative analysis of IR spectra of S-and R-isomers differing in the configuration of OH groups in the side chain of biologically
active 24-epi-and 28-homocastasterones and 24-epi-and 28-homobrassinolides is carried out. Stretching vibration frequencies
of H-bonded OH groups of isomers of corresponding brassinosteroids practically coincide. The optical density in maxima of
these bands is higher in spectra of the R-isomers. Alteration in the configuration of the OH groups weakly influences also
the band intensities of CH3, CH2, and CH groups. Band intensities of stretching vibrations of associated C=O groups of S-and R-isomers also neglibibly differ
from each other. Their frequency characteristics do not experience substantial changes. These features differ considerably
in IR spectra of castasterones and brassinolides. For castasterones, the difference in frequencies of band maxima of free
and bound C=O groups amounts to ∼15 cm−1; for brassinolides, 23 cm−1. Intensities of both bands are approximately equal in spectra of castasterones. The band intensity of free C=O groups of
brassinolides is considerably lower than that of H-bonded ones. The above spectral differences can be used to identify these
brassinosteroids. Frequencies of both symmetric and antisymmetric deformation vibrations of CH3 and CH2 groups are close in spectra of all brassinosteroids studied. The frequency of CH2 in a CH2-OC group belongs only to brassinolides; of deformation vibrations of CH in a CH-C=O group, to castasterones. The frequency
of stretching vibrations of C-O-C and C-O groups is observed only in spectra of brassinolides. In the region 1130–900 cm−1 of IR spectra of brassinosteroids, stretching vibrations of CC, CCH, and C-OH groups are predominantly observed. In the frequency
range 1130–995 cm−1, the optical density of band maxima of S-isomers is higher than that of R-isomers, which can be used to identify isomers.
At the same time frequencies of corresponding bands of isomers practically coincide. Differences in the structure of the side
chain of brassinosteroids do not influence essentially the frequency characteristics of the IR spectra. The exception is the
band related to stretching vibrations ν(C23-OH) of the side chain which features a considerable frequency νmax ≈ 983 cm−1 only in spectra of R-isomers of homocastasterone and brassinolide.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 5, pp. 623–630, September–October, 2008. 相似文献
20.
A. O. Rybaltovskii V. I. Gerasimova Yu. S. Zavorotnyi A. Yu. Chebrova 《Journal of Applied Spectroscopy》2009,76(1):93-100
We have studied the photoluminescence (PL) spectra of Eu3+ ions and the decay kinetics for the photoluminescence intensity on exposure to temperature and UV radiation in polypropylene
and oligo(urethane methacrylate) (OUM) doped with Eu(fod)3 molecules (fod = 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octadione) by soaking in a supercritical CO2 solution. We have established that the decay kinetics for the photoluminescence intensity on exposure to UV radiation depends
on the temperature of the sample and the concentration of the dopant in it. Based on studies of the spectral characteristics
of doped OUM samples, we suggest that this material can be used as a two-color luminescent temperature sensor.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 1, pp. 104-111, January-February, 2009. 相似文献