共查询到20条相似文献,搜索用时 218 毫秒
1.
G. A. Komandin V. I. Torgashev A. A. Volkov O. E. Porodinkov I. E. Spektor A. A. Bush 《Physics of the Solid State》2010,52(4):734-743
Reflection and transmission infrared spectra of BiFeO3 ceramic samples have been measured using submillimeter spectroscopy (on a backward-wave tube spectrometer) and Fourier-transform
infrared spectroscopy in the frequency range from 5 to 1000 cm−1 at temperatures in the range from 10 to 500 K. New resonant modes (probably, magnetic in nature) with the eigenfrequencies
decreasing with an increase in the temperature have been recorded in the range 10–30 cm−1 by IR spectroscopy for the first time. An additional absorption with a fairly large dielectric contribution has been revealed
in the range 30–60 cm−1. It has been demonstrated that the corresponding oscillators couple with both the lowest frequency phonon mode and the magnetic
subsystem. 相似文献
2.
E. S. Zhukova N. P. Aksenov B. P. Gorshunov Yu. G. Selivanov I. I. Zasavitskii D. Wu M. Dressel 《Physics of the Solid State》2011,53(4):810-814
The spectra of epitaxial Pb1 − x
Eu
x
Te (0 ≤ x ≤ 0.37) solid solution layers grown on BaF2 and Si substrates have been investigated over a wide frequency range 7–4000 cm−1 at temperatures of 5–300 K. Apart from the phonon and impurity absorption lines, the absorption in a local mode in PbEuTe
layers of substrates and buffer layers has been observed in the frequency range 110–114 cm−1. As the temperature decreases from 300 to 5 K, the transverse phonon mode softens from 33.0 to 19.5 cm−1. 相似文献
3.
Optical absorption in MnGaInS4 single crystals has been studied. Direct and indirect optical transitions are found to occur in the range of photon energies
of 2.37–2.74 eV and in the temperature range of 83–270 K. The temperature dependence of the band gap has been determined;
its temperature coefficients E
gd
and E
gi
are −5.06 × 10−4 and −5.35 × 10−4 eV/K, respectively. MnGaInS4 single crystals exhibit anisotropy in polarized light at the absorption edge; the nature of
this anisotropy is explained. 相似文献
4.
A. A. Voronkov B. P. Gorshunov V. S. Nozdrin E. S. Zhukova T. Matsuoka K. Tanaka S. Miyasaka S. Tajima M. Dressel 《JETP Letters》2012,94(9):708-713
The spectra of the conductivity and dielectric constant of La1.87Sr0.13CuO4 cuprate have been directly measured in the frequency range of 0.3 to 1.2 THz (10–40 cm−1) and the temperature range of 5 to 300 K in the E | c polarization (the electric field vector of radiation is perpendicular to the copper-oxygen planes). Excitation has been observed
in the superconducting phase, and its nature has been attributed to the transverse optical excitation of the condensate of
Cooper pairs, which appears because Josephson junctions between CuO planes are modulated due to in-plane magnetic and charge
stripes. Additional quasiparticle absorption of unknown origin has been detected at frequencies below ≈15 cm−1 at liquid helium temperatures. 相似文献
5.
We obtain experimental data on the complex refractive index N = n+ik of petroleum, five petroleum oils, and water-petroleum
emulsion in the frequency range f = 75–120 GHz. Measurements were performed in a quasioptical equipment with a backward-wave
oscillator generating the radiation and an OAP-7 optical-acoustic receivers for a temperature of 27°C of studied liquids.
The refractive indices n of petroleum and oil have a weak negative dispersion (dn/df < 0) and close values. At a frequency of 100 GHz, they lie in the range n = 1.477–1.495. The absorption indices k have different
frequency dependences such that k increases for four oils, while it decreases for petroleum and SM-4.5 oil with increasing
f. At the frequency f = 100 GHz, the values of k vary in a wide range from 2.4 · 10−4 to 1.7 · 10−3. The measurement results for petroleum and oils are compared with experimental results obtained by other authors. The frequency
dependences of n and k of water-petroleum emulsion for water concentrations 0.11% and 0.58% are compared with the data calculated
using various analytical models of dielectric mixtures. The dependences n(f) and k(f) calculated by the Kubo-Nakamura formula
are the closest to the experimental data.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 50, No. 6, pp. 485–495, June 2007. 相似文献
6.
Electric and dielectric properties of solution-gas interface grown AgCl thin film capacitors (Al/AgCl/Al) of various thicknesses
have been studied in the frequency range 101–106 Hz at various temperatures (303–393 K). I–V characteristics show ohmic, space-charge-limited, and thermionic emission conduction
mechanisms to operate at low, intermediate and high voltages respectively. Capacitance decreases with increasing film thickness
and applied frequency while it increases with increase of temperature. Loss factor (tanδ), which shows a pronounced minimum with frequency, increases with the rise of temperature and (tanδ)min shifts to a higher frequency. The large values of capacitance and dielectric constant (ɛ) in the low frequency region indicate the possibility of an interfacial polarization mechanism to operate in this region
while electronic and ionic polarizations dominate in the high frequency region. 相似文献
7.
We have measured the absorption cross sections of oxygen molecules in oxygen and in an oxygen-argon mixture heated by a shock
wave, in the wavelength range 190–250 nm at temperatures of 1500–7000 K, for thermal equilibrium conditions behind the shock
wave front. Analysis of the absorption cross sections obtained allowed us to select a data set that adequately describes the
absorption characteristics of the electronic transition X3Σ
g
−
→ B3Σ
u
−
for the oxygen molecule.
In order to approximate the temperature dependence of these cross sections at a temperature of 1500–4500 K, we chose the function
σ(λ, T) = σ0(λ)(1 − exp (−θ/T)) exp (− n*θ/T) where θ0 = 1.4·10−17, 1.4·10−17, 1.2·10− 17, and 1.3·10−17 cm2, n* = 3.1, 4.1, 5.6, and 7.47 for wavelengths 190, 210, 230, and 250 nm, respectively; θ = 2240 K is the characteristic temperature
of the O2 molecules. The approximation error was 19–25% and did not exceed the experimental error.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 1, pp. 13–17, January–February, 2006. 相似文献
8.
S. V. Demishev A. V. Semeno N. E. Sluchanko N. A. Samarin J. Singleton A. Ardavan S. J. Blundell W. Hayes S. Kunii 《JETP Letters》1996,64(10):760-766
In undoped pure single crystals of the mixed valence compound SmB6 anomalous ESR absorption is observed in the frequency range v=40–120 GHz at temperatures of 1.8–4.2 K. The ESR for the case of the coherent ground state consists of two components corresponding
to g-factors g
1=1.907±0.003 and g
2=1.890±0.003. The amplitude of both ESR lines strongly depends on temperature in the temperature range studied: the amplitude
of the first line with g=g
1 increases and the amplitude of the second line decreases with temperature. A model based on consideration of intrinsic defects
in the SmB6 crystalline lattice, with a densit ∼1015−1016 cm−3, is suggested as an explanation for the anomalous ESR-behavior. In the frequency range v>70 GHz at T=4.2 K, in addition to the main ESR lines, a new magnetic resonance with a hysteretic field dependence is discovered.
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 10, 707–712 (25 November 1996)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
9.
Crystalline structure and optical spectroscopy of Er3+-doped KGd(WO4)2 single crystals 总被引:2,自引:0,他引:2
M.C. Pujol M. Rico C. Zaldo R. Solé V. Nikolov X. Solans M. Aguiló F. Díaz 《Applied physics. B, Lasers and optics》1999,68(2):187-197
4 )2 single crystals doped with Er3+ have been grown by the flux top-seeded-solution growth method. The crystallographic structure of the lattice has been refined,
being the lattice constants a=10.652(4), b=10.374(6), c=7.582(2) Å, β=130.80(2)°. The refractive index dispersion of the host
has been measured in the 350–1500 nm range. The optical absorption and photoluminescence properties of Er3+ have been characterised in the 5–300 K temperature range. At 5 K, the absorption and emission bands show the (2J+1)/2 multiplet
splittings expected for the C2 symmetry site of Er in the Gd site. The energy positions and halfwidths of the 72 sublevels observed have been tabulated
as well as the cross sections of the different multiplets. Six emission band sets have been observed under excitation of the
4F7/2 multiplet. The Judd–Ofelt (JO) parameters of Er3+ in KGW have been calculated: Ω2=8.90×10-20 cm2, Ω4=0.96×10-20 cm2, Ω6=0.82×10-20 cm2. Lifetimes of the 4S3/2, 4F9/2, and 4I11/2 multiplets have been measured in the 5–300 K range of temperature and compared with those calculated from the JO theory.
A reduction of the 4S3/2 and 4I11/2 measured lifetimes with increasing erbium concentration has been observed, moreover the presence of multiphonon non-radiative
processes is inferred from the temperature dependence of the lifetimes.
Received: 15 December 1997/Revised version: 10 July 1998 相似文献
10.
A. M. Efimov A. I. Ignat’ev N. V. Nikonorov E. S. Postnikov 《Optics and Spectroscopy》2011,111(3):426-433
We have measured the UV absorption spectra of photothermorefractive glasses of the system Na2O-ZnO-Al2O3-NaF-SiO2 doped by cerium oxide in the range of (2.8–5.0) × 104 cm−1 (360–200 nm). The spectra have been processed by the method of dispersion analysis based on the analytical convolution model
for the complex dielectric function of glasses. We show that the absorption band centered at 3.3 × 104 cm−1 (∼303 nm) that is attributed to the transition 2F
5/2 → 5d in the Ce3+ ion, is an envelope of three spectral components. The broad absorption range (3.5–4.7) × 104 cm−1 (200–270 nm) that is commonly interpreted as a charge transfer band of the Ce(IV) valence state, is an envelope of at least
three spectral components. 相似文献
11.
A. K. Chaudhary A. M. Rudra P. Kumbhakar G. C. Bhar 《Journal of Applied Spectroscopy》2007,74(4):571-577
We report a technique for the efficient generation of tunable coherent deep UV radiation and its application in studies of
RDX and TNT at the ppm level on the basis of their absorption characteristics. The obtained experimental absorption data are
compared with conventional spectrophotometric data. The UV radiation in the range 200–260 nm has been generated by the type-I
noncollinear third harmonic of the dye laser radiation (600–700 nm) and also by sum frequency mixing (SFM) of Nd:YAG output
(1064 nm) with the second harmonic of the dye laser in β-barium borate (BBO) crystal. The maximum conversion efficiency of
the generated signal is estimated to be 57.5% at λ = 218.9 nm wavelength. Apart from measurements of the absorbance of RDX
and TNT at different concentrations in their respective solutions, the minimum detection concentrations have also been ascertained.
The estimated minimum detectable concentration of RDX is 8.47·10−9 M, whereas that for TNT is 35.7·10−9 M. The data were obtained using only ∼100 μJ/pulse of laser energy.
Published in Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 6, pp. 516–521, July–August, 2007. 相似文献
12.
We report the vibrational properties of lithium-intercalated SnSySe2−y (0≤y≤2) layered compounds. Infrared absorption spectra have been recorded as a function of temperature in the frequency range
50–600 cm−1. The new bands are interpreted as vibrational modes of lithium atoms against the nearest-neighbouring-chalcogen atoms located
in the van der Waals gap. Results are analyzed in terms of stretching vibrations of Li-S4 and Li-S6 entities. From a comparison of the spectra, it is concluded that lithium ions are more likely to occupy tetrahedral sites
in the lithium-rich phases. Using a simple model of lattice dynamics, the coupling force constants are determined and compared
with those of the pristine materials.
Paper presented at the 2nd Euroconference on Solid State Ionics, Funchal, Madeira, Portugal, Sept. 10–16, 1995 相似文献
13.
Prediction and Measurement of Electron Density and Collision Frequency in a Weakly Ionised Pine Fire
Kgakgamatso Mphale Mohan Jacob Mal. Heron 《International Journal of Infrared and Millimeter Waves》2007,28(3):251-262
Pine litter flame is a weakly ionised medium. Electron-neutral collisions are a dominant form of particle interaction in the
flame. Assuming flame electrons to be in thermal equilibrium with neutrals and average electron-neutral collision frequency
to be much higher than the plasma frequency, the propagation of microwaves through the flame is predicted to suffer signal
intensity loss. A controlled fire burner was constructed where various natural vegetation species could be used as fuel. The
burner was equipped with thermocouples and used as a cavity for microwaves with a laboratory quality network analyzer to measure
wave attenuation. Electron density and collision frequency were then calculated from the measured attenuation. The parameters
are important for numerical prediction of electromagnetic wave propagation in wildfire environments. A controlled pine litter
fire with a maximum flame temperature of 1080 K was set in the burner and microwaves (8–10.5 GHz) were caused to propagate
through the flame. A microwave signal loss of 1.6–5.8 dB was measured within the frequency range. Based on the measured attenuation,
electron density and electron-neutral collision frequency in pine fire were calculated to range from 0.51–1.35 × 1016 m−3 and 3.43–5.97 × 1010 s−1 respectively. 相似文献
14.
We study experimentally the frequency dependences of the refractive index n and the absorption coefficient k of distilled,
sea, and river water. The measurements were performed using a quasioptical device with a backward-wave oscillator as the radiation
source and OAP-7 optical-acoustic receivers at a water temperature of 27°C in the cell. The quantities n and k were determined
from the measured transmission and reflection coefficients of the cell with water by means of joint numerical solution of
the equations for these quantities. For distilled water in the frequency range f = 75–120 GHz, we obtained n = 6.142–3.926
· 10–2f[GHz] + 1.307 · 10–4(f[GHz])2 and k = 3.607–2.101 · 10−2 f[GHz] + 5.252 · 10–5(f[GHz])2. On the whole, these data are in good agreement with the measurement results obtained by other authors at several frequencies
of the indicated range and coincide with the calculation data based on the models by Meissner and Wentz and by Liebe et al.
within the limits of the rms determination errors 0.05 and 0.02 for the parameters n and k, respectively. The values of n
and k for different seawater samples and river water containing insoluble admixtures coincide with the values of these quantities
for distilled water within the limits of the experimental measurement errors 3–5% and 1–2%, respectively. The dependences
n(f) and k(f) obtained experimentally for seawater are compared with those calculated on the basis of the developed models.
Measurements of the transmission spectrum of a cell with double distilled water were performed for low power density of radiation
(less than μW/cm2) to reproduce the effect of water resonant transparency reported many times in the literature. Our measurements did not reveal
any resonant features in the spectral behavior of the refractive index n and the absorption coefficient k of water and gave
the same result as for a power density exceeding the threshold of appearance of this effect.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 6, pp. 489–501, June 2006. 相似文献
15.
M. D. Volnyanskii S. N. Plyaka M. P. Trubitsyn Yahia A. H. Obaidat 《Physics of the Solid State》2012,54(3):499-503
The electrical properties of a lithium heptagermanate (Li2Ge7O15) crystal have been studied in DC and AC measuring fields at temperatures from 500 to 700 K. In a DC field, a substantial
decrease of electrical conductivity σ with time has been detected. On the basis of kinetic dependences σ(t), estimates of the charge carrier diffusion coefficient D have been obtained. In the frequency range 101–105 Hz, the spectra of complex impedance ρ*(f) have been measured. The analysis of diagrams in the complex plane (ρ″–ρ′) has been performed within the equivalent circuit
approach. It has been shown that, in the considered temperature and frequency intervals, the electrical properties of Li2Ge7O15 crystals have been determined by the hopping conduction of interstitial lithium ions A
Li and accumulation of charge carriers near the blocking Pt electrodes. 相似文献
16.
By adding cubic and quartic phonon anharmonic interactions in the pseudospin lattice coupled mode (PLCM) model for KDP-type
crystals and using double-time temperature dependent Green's function method, expressions for soft mode frequency, dielectric
constant and dielectric tangent loss are obtained. Using model parameters given by Ganguliet al [9] the dielectric losses are calculated for KDP and DKDP crystals. In the microwave frequency range an increase in frequency
(1–35 GHz) is followed by an increase in dielectric tangent loss (1–35) at 98 K and (1–15) × 10−2 at 333 K for KDP and DKDP crystals respectively. The dielectric tangent loss decreases from 0.052 to 0.042 for KDP crystals
with increase in temperature from 130 to 170 K and for DKDP crystals it decreases from 0.0166 to 0.0074 with an increase in
temperature from 230–343 K in their paraelectric phases at 10 GHz. This shows Curie-Weiss behavior of the dielectric tangent
loss 相似文献
17.
Composite materials used for electrode and electrolyte materials have been intensely studied in view of their advantages such
as higher conductivity and better operational performance compared to their single-phase counterparts. The present work aims
at studying the electrical and structural characteristics of a new composite electrolyte namely, (PbI2)
x
− (Ag2O–Cr2O3)100−x
where x = 5, 10, 15, 20, and 25 mol%, respectively, prepared by the melt quenching technique. The room temperature X-ray diffraction
spectra revealed certain crystalline phases in the samples. AC conductivity analysis for all the prepared samples was carried
out over the frequency range 1 MHz–20 Hz and in the temperature window 297–468 K. The room temperature conductivity values
were calculated to be in the order of 10−5–10−3 Scm−1. An Arrhenius dependence of temperature with conductivity was observed, and the activation energies calculated were found
to be in the range 0.27–0.31 eV. Furthermore, the total ionic transport number (t
i) values obtained for all these indicated the ionic nature of this system.
Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7–9, 2006. 相似文献
18.
B. I. Turko V. B. Kapustyanyk V. P. Rudyk M. V. Partika M. V. Kvasnytsya A. P. Vas’kiv 《Journal of Applied Spectroscopy》2007,74(2):310-312
We have studied the behavior of the intrinsic absorption edge in zinc oxide thin films in the temperature range 80–300 K.
We have observed that the intrinsic absorption edge in films with crystal sizes of ≈45 nm or larger is described by the empirical
Urbach’s rule, while in films with crystallite sizes of ≈15 nm, it is described by a modified Urbach’s rule. We have calculated
the effective frequency of phonons taking part in formation of the absorption edge.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 2, pp. 275–277, March–April, 2007. 相似文献
19.
D. I. Stasel’ko S. A. Tikhomirov O. V. Buganov A. S. Shcheulin A. E. Angervaks A. I. Ryskin 《Optics and Spectroscopy》2011,110(1):33-41
The kinetics of photoinduced absorption spectra of CdF2 crystals with bistable indium and gallium centers under femtosecond pulsed excitation has been experimentally investigated.
Based on the example of indium ions, it is shown that the transmission band in the absorption spectrum of deep centers is
formed for 0.8–1 ps, which significantly exceeds the photon absorption time. This process is interpreted as a result of displacement
of indium ion from the initial interstitial position to a site of neighboring unit cell; the displacement velocity is estimated
to be 200–250 m/s, a value close to the thermal velocity of this ion at room temperature. The times characteristic of the
formation of free polarons as a result of the displacement of neighboring lattice ions have been experimentally estimated
for the first time at a level of 0.8–1.2 ps. The capture times of free polarons by trivalent gallium and indium ions are estimated
(5 and 10 ps, respectively), as well as the corresponding cross sections (2 × 10−16 and 8 × 10−16 cm2). 相似文献
20.
The functions of the main indices of refraction n(ν) and absorption κ(ν) of uniaxial thin polyethylene terephthalate films
have been calculated by the experimental spectra of frustrated total reflection of s-and p-polarized radiation in the 700–760-cm−1 range. The κo(ν) maximum falls at the the 727-cm−1 frequency and the maximum of κe(ν) falls at the the 724-and 732-cm− 1 frequencies.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 6, pp. 756–759, November–December, 2005. 相似文献