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1.
Summary The spin-orbit parameter Δ, spin-lattice relaxation timeT
1, and spin-mixing parameter ɛ ofF
H(OH−) andF
H(CN−) centers in several alkali halides have been studied with magnetic circular dichroism at ∼2 K. A close comparison of the
experimental results before and after optically induced association of theF center with the molecular ion has been made. In crystals of NaCl structure the negative spin-orbit parameter Δ changes little
betweenF andF
H centers in the same host. For CsCl and CsBr two values of Δ have been derived forF
H(CN−) centers with axis parallel or perpendicular to the magnetic field. In all studied systems, the spin-lattice relaxation timeT
1 is already shorter before aggregation compared toF formation. The spin-mixing parameter ɛ decreases slightly forF
H(OH−) compared toF centers, while it increases drastically forF
H(CN−) defects and reaches its maximum possible value ɛ=0.5 in cesium halides. First attempts to interpret these magneto-optical
results will be presented.
In honour of Prof. Fausto Fumi on the occasion of his retirement from teaching. 相似文献
2.
Haijuan Chen Hong Li Xianglin Yang 《International Journal of Infrared and Millimeter Waves》1997,18(6):1369-1374
Soliton propagation and switching in twin-core nonlinear fibers with gain and loss have been investigated based on a pair
of coupled nonlinear Schr?dinger equations. We have found the fiber with equal amount of gain in both cores has the minimum
ascending energy Δɛ of 1.5K, while the fiber with a certain amount of gain in one core and the same amount of loss in the other core has the minimum
switching thresholdɛ
th of 2.05K. A new vector field is defined and its potential function is derived, which explains the switching behavior of the minimumɛ
th switch satisfactorily. 相似文献
3.
The asymptotics as ɛ → 0 of the spectrum of the shifted Laplace operator H = ɛΔ + ∂v on a two-dimensional compact surface of revolution homeomorphic to the sphere is described, where v is a vector field. 相似文献
4.
The influence of the frequency f of applied ac electric field on the time dependence of electric field induced deformations
of homeotropic nematic layers is studied numerically. Three kinds of nematic liquid crystals were considered:
– |
non-flexoelectric nematic with negative dielectric anisotropy, Δɛ < 0 相似文献
5.
The dielectric constant (ɛ′) and dielectric loss (ɛ″) for dilute solutions of sulfolane in carbon tetrachloride solution have been measured at 9.885 GHz at different temperatures
viz. 25°C, 30°C, 35°C and 40°C by using standard microwave techniques. Following the single frequency concentration variational
method, the dielectric relaxation time (τ) and dipole moment (μ) have been calculated. It is found that dielectric relaxation process can be treated as the rate process,
just like the viscous flow. Based on the above studies, monomer structure of sulfolane in carbon tetrachloride has been inferred.
Energy parameters (ΔH
g
, ΔF
g
, ΔS
g
) for dielectric relaxation process of sulfolane in carbon tetrachloride at 25°C, 30°C, 35°C and 40°C have been calculated
and compared with the corresponding energy parameters (ΔH
η
, ΔF
η
, ΔS
η
) for the viscous flow. 相似文献
6.
Viêt Hà Hoàng 《Communications in Mathematical Physics》2000,214(2):411-428
The paper considers the singularly perturbed Dirichlet problem −ɛΔu
ɛ+u
ɛ=f in a randomly perforated domain Ωɛ, which is obtained from a bounded open set Ω in R
N
after removing many holes of size ɛ
q
. The perforated domain is described in terms of an ergodic dynamical system acting on a probability space. Imposing certain
conditions on the domain, the behaviour of u
ɛ when ɛ→ 0 in Lebesgue spaces L
n
(Ω) is studied. Test functions together with the Birkhoff ergodic theorem are the main tools of analysis. The Poisson distribution
of holes of size ɛ
p
with the intensity λɛ−
r
is then considered. The above results apply in some cases; other cases are treated by the Wiener sausage approach.
Received: 15 December 1999 / Accepted: 14 April 2000 相似文献
7.
This paper reports on the first results obtained from the investigation of the effect of IR radiation on the low-temperature
(1.8 ≤ T ≤ 4.2 K) plasticity of solid hydrogen. It has been found that, when the samples are exposed to IR radiation, a drastic increment
ΔɛIR of the elongation per unit length ɛ (which was preliminarily achieved under a continuously applied mechanical stress σ =
const) occurs without an increase in the temperature of the samples. It has been revealed that the effect observed both in
the case of normal hydrogen (n-H2, 75% o-H2) and in the case of parahydrogen (p-H2, ∼0.2% o-H2) only for a sufficiently high power of the IR radiation source has a threshold character. The reverse deformation of solid
hydrogen is observed after the irradiation with a flux of IR photons is completed: the quantity ɛ rapidly decreases to values
provided only by the applied load. The appearance of jumps in the increment of deformation ΔɛIR
i
is interpreted as a consequence of the existence of the fundamental IR absorption band for solid hydrogens. It has been established
that, depending on the time t of exposure of the samples to IR radiation, the change in the quantity ΔɛIR
i
(t) obeys the logarithmic law, which is characteristic of the dislocation creep and observed in the case of unirradiated hydrogen.
It has also been found that, under multiple relatively long-term exposure to IR radiation, the constant α of the logarithmic
creep of n-H2 abruptly decreases, whereas the strength of both the n-H2 and p-H2 samples increases significantly, which indicates their explicit hardening (instead of the expected “superplastic” behavior
due to the exposure to IR irradiation). 相似文献
8.
The asymptotics as ɛ → 0 of the spectrum of the shifted Laplace operator H = ɛΔ + ∂
υ
on the standard two-dimensional sphere is described, where υ is a vector field.
Dedicated to the memory of Vladimir Borovikov 相似文献
9.
Amorphous structure generated by mechanical alloying (MA) is often used as a precursor for generating nanocomposites through
controlled devitrification. The amorphous forming composition range of ternary Al-Ni-Ti system was calculated using the extended
Miedema’s semi-empirical model. Eleven compositions of this system showing a wide range of negative enthalpy of mixing (−ΔH
mix) and amorphization (−ΔH
amor) of the constituent elements were selected for synthesis by MA. The Al88Ni6Ti6 alloy with relatively small negative ΔH
mix (−0.4 kJ/mol) and ΔHamor (−14.8 kJ/mol) became completely amorphous after 120 h of milling, which is possibly the first report of complete amorphization
of an Al-based rare earth element free Al-TM-TM system (TM = transition metal) by MA. The alloys of other compositions selected
had much more negative ΔHmix and Hamor; but they yielded either nanocomposites of partial amorphous and crystalline structure or no amorphous phase at all in the
as-milled condition, evidencing a high degree of stability of the intermetallic phases under the MA environment. Hence, the
negative ΔH
mix and ΔH
amor are not so reliable for predicting the amorphization in the present system by MA 相似文献
10.
The complex permittivity (ɛ = ɛ′ − iɛ″) of natural, modified, and irradiated zeolites as a function of the frequency of a variable electric field is measured.
For Ba2+-modified (doped) zeolite, the permittivity and dielectric loss tangent (tanδ) as functions of the electric field frequency
are found to decrease monotonically. When the irradiation dose rises to 105 cm−2, the dielectric loss tangent reaches a maximum and then, starting from a dose of 3 × 1016 cm−2, sharply drops. Such behavior of tanδ is assumed to be associated with Ba2+- and irradiation-induced structural modifications in the unit cell of zeolite. 相似文献
11.
Excess molar volumes (V
E) and deviation in isentropic compressibilities (Δβ
s) have been investigated from the density ρ and speed of sound u measurements of six binary liquid mixtures containing n-alkanes over the entire range of composition at 298.15 K. Excess
molar volume exhibits inversion in sign in one binary mixture, i.e., n-heptane + n-hexane. Remaining five binary mixtures,
n-heptane + toluene, cyclohexane + n-heptane, cyclohexane + n-hexane, toluene + n-hexane and n-decane + n-hexane show negative
excess molar volumes over the whole composition range. However, the large negative values of excess molar volume becomes domainant
in toluene + n-hexane mixture. Deviation in isentropic compressibility is negative over the whole range of composition in
the case of all the six binary mixtures. Existence of specific intermolecular interactions in the mixtures has been analyzed
in terms of excess molar volume and deviation in isentropic compressibility. 相似文献
12.
Dielectric relaxation measurements of formamide (FMD)-N,N-dimethylaminoethanol (DMAE) solvent mixtures have been carried out over the entire concentration range using time domain
reflectometry technique at 25, 35 and 45°C in the frequency range of 10 MHz to 20 GHz. The mixtures exhibit a principle dispersion
of the Davidson-Cole relaxation type at microwave frequencies. Bilinear calibration method is used to obtain complex permittivity
ɛ*(ω) from complex reflection coefficient ρ*(ω) over the frequency range of 10 MHz to 10 GHz. The excess permittivity (ɛ
E), excess inverse relaxation time (1/τ)E, Kirkwood correlation factor (g
eff), activation energy and Bruggeman factor (f
B) are also calculated to study the solute-solvent interaction.
相似文献
13.
I. V. Zolotukhin S. V. Spitsina L. I. Yanchenko L. N. Korotkov 《Physics of the Solid State》1999,41(11):1891-1893
Macroscopic fractal aggregates of KH2PH4 (KDP) measuring up to 500 μm have been obtained. The fractal structure forms as a result of the precipitation of KDP particles
from a supersaturated aqueous solution in the presence of a temperature gradient followed by a diffusioncontrolled mechanism
of aggregation. The electron-microscopic analysis performed has shown that the fractals are formed predominantly from crystallites
of the tetragonal modification measuring ∼1 μm. The dielectric constant (ɛ) of fractal KH2PO4 has been measured in the temperature range 80–300 K. A characteristic anomaly has been discovered on the ɛ(T) curve in the vicinity of 122 K, which attests to a ferroelectric phase transition. The absolute value of ɛ is significantly smaller than the components ɛ
11 and ɛ
33 for KH2PO4.
Fiz. Tverd. Tela (St. Petersburg) 41, 2059–2061 (November 1999) 相似文献
14.
Eighteen binary mixtures of 4-pentyloxy-4′-cyanobiphenyl (5OCB) and 4, 4′-di(alkoxy)azoxybenzenes (nOAB) with n = 5, 6, and
7 at different concentrations have been studied in detail. Over a wide concentration range, induced SmA phase was observed
in all the mixtures except in one. In most of the mixtures, the refractive indices no, ne, and Δn lie between the values of
pure components. The optical birefringence of the mixtures is found to decrease non-additively with concentration. The molecular
polarizability anisotropy and the orientational order parameter <P2> of the mixtures were calculated. Nature of variation of polarizability anisotropy with concentration is similar to that
of Δn. In allmixtures <P2> is more in smectic phase than in nematic phase and it also shows non-additive behaviour. Observed <P2> values of the mixtures were compared with McMillan’s and Maier-Saupe theoretical values and good agreement is found in some
mixtures. The transition temperatures obtained by fitting <P2> data to McMillan’s theory agree with the observed values within a few degrees. Ratio of elastic constants K33 and K11 is determined for mixtures having nematic phase and found to diverge at TNA transition point. 相似文献
15.
FePS3 is a layered antiferromagnet (T
N=123 K) with a marked Ising anisotropy in magnetic properties. The anisotropy arises from the combined effect of the trigonal
distortion from octahedral symmetry and spin-orbit coupling on the orbitally degenerate5
T
2g
ground state of the Fe2+ ion. The anisotropic paramagnetic susceptibilities are interpreted in terms of the zero field Hamiltonian, ℋ=Σi [δ(L
iz
2
−2)+|λ|L
i
.S
i
]−Σ
ij
J
ij
S
i
.S
j
. The crystal field trigonal distortion parameter Δ, the spin-orbit coupling λ and the isotropic Heisenberg exchange,J
ij, were evaluated from an analysis of the high temperature paramagnetic susceptibility data using the Correlated Effective
Field (CEF) theory for many-body magnetism developed by Lines. Good agreement with experiment were obtained for Δ/k=215.5 K; λ/k=166.5 K;J
nn
k=27.7 K; andJ
nnn
k=−2.3 K. Using these values of the crystal field and exchange parameters the CEF predicts aT
N=122 K for FePS3, which is remarkably close to the observed value of theT
N. The accuracy of the CEF approximation was also ascertained by comparing the calculated susceptibilities in the CEF with
the experimental susceptibility for the isotropic Heisenberg layered antiferromagnet MnPS3, for which the high temperature series expansion susceptibility is available. 相似文献
16.
The effects of explicit Δ degrees of freedom on trinuclear binding energy and structure are investigated using the Argonne
V28Q Δ model. Separate dispersive effects, one- and two-Δ three-body force effects, and one- and two-Δ probabilities are determined
for the triton. Some new results are also given for the Hannover and Argonne V28 Δ models, and V28Q trinuclear Δ effects are
compared with those of these other models. Considerable consistency among the models is found, suggesting a coherent qualitative
picture of trinuclear Δ effects.
Received June 8, 1994; accepted for publication September 27, 1994 相似文献
17.
Kenneth Bober Robert H. Giles Jerry Waldman 《International Journal of Infrared and Millimeter Waves》1997,18(1):101-123
The microwave permittivity (ɛr) and permeability (μr) of composite materials are tailored by adding various loading agents to a host plastic and are subsequently modeled using
the Maxwell Garnett theory and second order polynomials. With the addition of manganese zinc ferrite, strontium ferrite, nickel
zinc ferrite, barium tetratitanate and graphite powders, materials with values of ɛ′, e″, μ′, μ″ as high as 22, 5, 2.5 and
1.7 have been obtained. Permittivity and permeability data are calculated at 2.0245 GHz from reflection and transmission measurements
performed in a 7 mm coaxial test line. The Maxwell Garnett (MG) theory successfully models ɛr if the filling factor is less than 0.30 and ratio |ɛ1| (host)/ |ɛ2| (powder) is greater than 0.04. As this ratio decreases, the MG theory is shown to be independent of ɛ2 and second order polynomials are used to effectively model the dielectric constant. Polynomials are also used for the ferrite
composites because it was determined that the MG theory was unable to model μr. This deficiency is attributed to the difference of domain structures that exist in powdered and sintered ferrites. 相似文献
18.
Using the method of optical probing, we investigated the effect exerted by the concentration of the substance and the temperature
of the solution on the spectral behavior of the difference in the refractive indices of ordinary and extraordinary waves Δn=no−ne of excited solutions of Rhodamine 6G and 3,6-tetramethyldiaminophthalimide in glycerin. We established that laser-excitation-induced
quasicrystallinity of the indicated solutions in probing in the fluorescence band, which is characterized by the magnitude
of the difference between the refractive indices Δn, increases with increase in the concentration of the substance. This increase
in the crystallinity of the system with increase in the concentration of the substance (the activator) is possible up to the
instant of the appearance of intermolecular interaction of the molecules.
To whom correspondence should be addressed.
Reported at the Second International Scientific and Technical Conference on Quantum Electronics, Minsk, November 23–25, 1998.
Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 5, pp. 672–674, September–October, 1999. 相似文献
19.
A. I. Sukachev 《Moscow University Physics Bulletin》2009,64(4):374-378
Mixing of neutral K
0 mesons is studied in the framework of the minimal supersymmetric model (MSSM) with a Yukawa type II sector and explicit violation
of CP invariance in the Higgs potential. Mixing parameters Δm
LS
and ɛ are calculated in the limit of the four-fermion approximation with charged Higgs boson exchange. This work specifies
the data presented in [1] more precisely and, taking into account the influence of new contributions on the above observables,
proves the small degree of supersymmetric effects for a system of K
0 mesons. 相似文献
20.
Loncarević I Budinski-Petković Lj Vrhovac SB 《The European physical journal. E, Soft matter》2007,24(1):19-26
Random sequential adsorption of binary mixtures of extended objects on a two-dimensional triangular lattice is studied numerically
by means of Monte Carlo simulations. The depositing objects are formed by self-avoiding random walks on the lattice. We concentrate
here on the influence of the symmetry properties of the shapes on the kinetics of the deposition processes in two-component
mixtures. Approach to the jamming limit in the case of mixtures is found to be exponential, of the form: θ(t) ∼ θjam - Δθ exp(- t/σ), and the values of the parameter σ are determined by the order of symmetry of the less symmetric object in the mixture.
Depending on the local geometry of the objects making the mixture, jamming coverage of a mixture can be either greater than
both single-component jamming coverages or it can be in between these values. Results of the simulations for various fractional
concentrations of the objects in the mixture are also presented. 相似文献
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