共查询到20条相似文献,搜索用时 15 毫秒
1.
M. A. Algatti R. P. Mota R. Y. Honda M. E. Kayama K. G. Kostov R. S. Fernandes T. C.A.M. Azevedo N. C. Cruz 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(2):325-328
This paper deals with plasma polymerization processes of diethylene glycol dimethyl ether. Plasmas were produced at 150 mtorr
in the range of 10 W to 40 W of RF power. Films were grown on silicon and quartz substrates. Molecular structure of plasma
polymerized films and their optical properties were analyzed by Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible
spectroscopy. The IR spectra show C–H stretching at 3000–2900 cm-1, C=O stretching at 1730–1650 cm-1, C–H bending at 1440–1380 cm-1, C–O and C–O–C stretching at 1200–1000 cm-1. The concentrations of C–H, C–O and C–O–C were investigated for different values of RF power. It can be seen that the C–H
concentration increases from 0.55 to 1.0 au (arbitrary unit) with the increase of RF power from 10 to 40 W. The concentration
of C–O and C–O–C decreases from 1.0 to 0.5 au in the same range of RF power. The refraction index increased from 1.47 to 1.61
with the increase of RF power. The optical gap calculated from absorption coefficient decreased from 5.15 to 3.35 eV with
the increase of power. Due to its optical and hydrophilic characteristics these films can be applied, for instance, as glass
lens coatings for ophthalmic applications. 相似文献
2.
Youguo Yan Lixia Zhou Jianying Zou Ye Zhang 《Applied Physics A: Materials Science & Processing》2009,94(3):559-565
Novel ZnO tetrapod-shaped nanostructures with pearl-necklace-shaped arms were successfully synthesized using mixture of Zn,
ZnO, and carbon powder as source. The definite supersaturation ratio provided by Zn, ZnO, and carbon powder was considered
as the crucial factor of determining the formation of this kind of structure, and a negative feedback growth model combined
with octahedral nucleation mechanism was proposed. Two other comparative experiments were also conducted to study the growth
behavior of reagent species under different supersaturation ratios. Our experiments provided a beneficial experimental exploration
in controlled growth of nanostructures through modulating supersaturation ratio by source, and these obtained novel nanostructures
were also expected to have potential application as functional blocks in nanodevices. Furthermore, the study of photoluminescence
indicated that the physical properties were strongly dependent on the crystal structure. 相似文献
3.
Formation of the plasma potential in a plasma that contains energetic electrons and is bounded by a floating collector that
emits electrons is studied theoretically. The problem is treated by a static. kinetic plasma-sheath model of Schwager and
Birdsall [Phys. Fluids B2 (1990) 1057], which we have extended in order to include additional energetic electron population. The distribution of these
electrons is assumed to be a high-temperature Maxwellian. They are called hot electrons. In the paper we study effects of
the density and temperature of the hot electrons on the formation of the plasma potential. The model shows that for certain
densities and temperatures of the hot electron population plasmas with two different plasma potentials can coexist in the
system. These two plasmas are separated spatially by a double layer. For the case when there is no emission of electrons from
the collector, results of the model are compared with computer simulation and very good agreement between the model and the
simulation is found. The simulation also confirms existence of two plasmas with two different potentials separated by a double
layer. 相似文献
4.
S.-G. Cheng Y. X. Xing X. C. Xie Q.-F. Sun 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,67(4):551-557
The Josephson current through an Aharonov-Bohm (AB)
interferometer, in which a quantum dot (QD) is situated on one arm
and a magnetic flux Φ threads through the ring, has been
investigated. In the presence of the magnetic flux, the relation
between the Josephson current and the superconductor phase is
complex, and the system can be adjusted to π junction by either
modulating the magnetic flux or the QD’s energy level
εd. Due to the electron-hole symmetry, the Josephson
current I has the property
I(εd,Φ)=I(-εd,Φ+π). The Josephson
current exhibits a jump when a pair of Andreev bound states aligns
with the Fermi energy. The condition for the current jump is given.
Particularly, we find that the position of the current jump and the
position of the maximum value of the critical current Ic are
identical. Due to the interference between the two paths, the
critical current Ic versus the QD’s level εd shows a
typical Fano shape, which is similar to the Fano effect in the
corresponding normal device. However they also show some
differences. For example, the critical current never reaches zero
for any parameters, while the current in the normal device can reach
zero at the destruction point. 相似文献
5.
We study wave equations with energy-dependent potentials. Simple analytical models are found useful to illustrate difficulties
encountered with the calculation and interpretation of observables. A formal analysis shows under which conditions such equations
can be handled as evolution equation of quantum theory with an energy-dependent potential. Once these conditions are met,
such theory can be transformed into ordinary quantum theory.
This work was supported by the agreement between IN2P3 and ASCR (collaboration no. 97-13) and by the Grant Agency of ASCR
(J.M., grant No.A1048305). 相似文献
6.
The energy of ground1,3S-states of negative positronium ion in the hyperspherical coordinates method has been calculated in Born-Oppenheimer and
adiabatic approximations accounting the contribution of angle and radial correlation. Quasi-crossing points for autodetaching
adiabatic potentials were revealed, which forms a structure in nonadiabatic potential. The received energy values have been
compared with results of calculations performed using other methods. It was shown that in order to receive energy values with
accuracy of 10−4 a.u. it is necessary to include more than 70 elements into the basis for determination of adiabatic potentials or to use
Padé approximation on the basis dimension.
Presented at the 11th Colloquium “Quantum Groups and Integrable Systems”, Prague, 20–22 June 2002.
The work is supported by the Slovak Agency for Science, Grant 2/7157/20. 相似文献
7.
Curvature and external electric field effects on the persistent current in chiral toroidal carbon nanotubes 总被引:1,自引:0,他引:1
N. Xu J. W. Ding H. B. Chen M. M. Ma 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,67(1):71-75
Taking into account the intrinsic curvature, we calculate the persistent currents (Ipcs) in chiral toroidal carbon nanotubes (TCNs) by developing the supercell approach. It is shown that in the presence of curvature,
the typical current (Ity) oscillates with the unit cell number (P) and tends to be zero, while it damps exponentially in the absence of curvature.
Due to the curvature effects, especially, a paramagnetism-diamagnetism transition is observed in chiral TCNs, depending on
the ring diameter and chirality. In addition, the effect of external electric field energy (Eef) on persistent current is also explored. It is shown that in the presence of electric field, Ity vary unmonotonously with Eef. A pronounced peak of Ity is obtained at high Eef region. By modulating the value of Eef, a paramagnetism-diamagnetism or diamagnetism- paramagnetism transition is observed. 相似文献
8.
An analysis of the photofission reactions in the quasi-deuteron energy range of photonuclear absorption (30–140 MeV) has been performed for209Bi and238U nuclei. Experimental cross section data available in the literature have been compared with calculated values obtained from a model in which the incoming photon is assumed to be absorbed by a neutron-proton pair (Levinger's quasi-deuteron photoabsorption), followed by a mechanism of evaporation-fission competition for the excited residual nuclei. The model has been shown to reproduce the main experimental features of209Bi and238U photofission cross section, although unexplained differences still remain in the case of238U-fission by 30– 50 MeV incident photons. 相似文献
9.
When a magnetic fluid is subjected to a magnetic field, a part of the magnetic particles in the fluid agglomerates to form
chains. Thus, the ferrofluid becomes optically anisotropic. In this work we describe optically observed patterns in some magnetic
fluid films in applied parallel magnetic fields and optical effects of these, especially the optical transmittance. The most
interesting experimental observation is that concerning the time dependence of relative transmittivity
. For kerosene base ferrofluids
relax rapidly at coupling and decoupling magnetic field, but for a transformer-oil magnetic fluid the relaxation times can
attain (5–10) minutes, depending on the intensity of applied magnetic field. 相似文献
10.
Enrico?Da?Como Esther?Scheler Peter?Strohriegl John?M.?Lupton Jochen?Feldmann 《Applied Physics A: Materials Science & Processing》2009,95(1):61-66
Polyfluorene represents a unique model to study the influence of intramolecular conformation on the electronic properties
of chromophores with an extended π-conjugation. According to the degree of planarity between the adjacent repeat units the electronic and optical properties
can change substantially. This peculiar spectroscopic behavior has been described by identifying different phases, namely
the glassy, the γ- and the β-phase. Here, we present low-temperature single-molecule spectroscopy of a series of oligofluorenes differing in the number
of monomeric units, in order to gain information on the influence of chain length on the polymorphism. By monitoring the energy
of the 0-0 transition we have classified single molecules belonging to the different phases. We demonstrate that a large number
of molecules start to form the β-phase only when more than 9 repeat units constitute the molecular chain. The implications for the control of morphology in
polyfluorene thin films are discussed. 相似文献
11.
Takeshi Yasuda Masatoshi Saito Hiroaki Nakamura Tetsuo Tsutsui 《Applied Physics A: Materials Science & Processing》2009,95(1):179-183
We have studied the electronic excitations of fluorinated copper phthalocyanine, CuPcF16, thin films using electron energy-loss spectroscopy in transmission. This allowed for the derivation of the dielectric function
in a wide energy range. Furthermore, we have analyzed the lowest excitation feature using a Lorentz model, which enabled the
determination of the dielectric background in the energy range of the gap excitation, and an analysis of the momentum dependence
of the spectral intensities at low energies. 相似文献
12.
The glass transition temperature of poly (maleic anhydride-alt-1-octadecen) and poly (styreneco-maleic anhydride) cumene-terminated
thin films has been measured by mechanical relaxation of Langmuir films of these polymers. The dynamical properties show glass-like
features (non-Arrhenius relaxation times and non-Debye mechanical response) interpreted by the coupling model. The glass transition
temperature values determined by a mechanical relaxation experiment (step-compression) agree very well with those obtained
by surface potential measurements. It is found that the glass transition temperature values in thin films decrease by about
100K as compared with those corresponding to the bulk polymers. The coadsorption of the water-insoluble surfactant DODAB decreases
the glass transition temperature. 相似文献
13.
14.
Albert?Mihranyan Mortadha?Muhel Maria?Str?mme 《Applied Physics A: Materials Science & Processing》2009,94(2):299-305
The dissolution process of sparingly soluble CaCO3 microparticles and how the fractal surface dimension of the particles changes during dissolution is analyzed. The particles
and the dissolution process are studied using scanning electron microscopy, X-ray diffraction, nitrogen adsorption, laser
diffraction and conductance measurements. Ball milling of the particles is shown to maintain the particle crystallinity, and
to introduce an increased fractal surface dimension in the 1–10 μm size range. Dissolution is found to increase the surface
dimension of initially smooth particles and to maintain the fractal surface roughness of milled particles. The dissolution
process increases the relative number of small particles (50 nm–1 μm) whereas the larger ones decrease in size. The solubility
of the milled fractal particles was ∼1.8 times higher than that for the initially smooth ones. The presented findings show
that developing methods for increasing the fractal surface roughness of particles should be of interest for improving the
solubility of poorly soluble drug candidates. 相似文献
15.
Using the trial-function method, the general solution of the Schrödinger equation for the time-dependent linear potential is obtained. Based on the Heisenberg correspondence principle, the solution of the classical equation of motion is derived from the quantum matrix elements. 相似文献
16.
A. E. Bernardini 《The European Physical Journal C - Particles and Fields》2008,56(4):545-556
We point out some incompatibilities which appear when one applies the stationary phase method for deriving phase times to
obtain the spatial localization of wave packets scattered by a unidimensional potential barrier. We concentrate on the above
barrier diffusion problem where the wave packet collision implies the possibility of multiple reflected and transmitted wave
packets, which, depending on the boundary conditions, can overlap or stand in relative separation in space. We demonstrate
that the indiscriminate use of the method for such a particular configuration leads to paradoxical results for which the correct
interpretation, confirmed by analytical/numerical calculations, imposes the necessity of the appearance of multiple peaks
as a consequence of multiple reflections by the barrier steps.
Also at Instituto de Física Gleb Wataghin, UNICAMP, PO Box 6165, 13083-970 Campinas, SP, Brazil. 相似文献
17.
L. Kuna C. Sommer E. Zinterl J. R. Krenn P. Pachler P. Hartmann S. Tasch G. Leising F. P. Wenzl 《Applied Physics A: Materials Science & Processing》2008,93(2):421-427
We report on the micro-fabrication of diffractive optical elements (DOEs) such as 1D, 2D and concentric grating structures
inside the volume of thin silicone films by femtosecond laser direct writing. In addition, we show that such structures can
also be integrated into silicone films that act as encapsulation layers of high power light-emitting diodes. The latter strategy
opens new possibilities to homogenize and to control the light emitted from such devices. 相似文献
18.
In the Shallow Water’ 06 experiment, two L-shape arrays (ARRAY52 and ARRAY32) were deployed. The vertical line array (VLA)
components of both ARRAY52 and ARRAY32 were exactly perpendicular to the direction of sound propagation. The horizontal line
array (HLA) component of ARRAY52 was exactly perpendicular to the direction of sound propagation. The HLA component of ARRAY32
was exactly parallel to the direction of sound propagation. This configuration offered an opportunity to simultaneously analyze
the three dimensional (3-D) spatial coherences: vertical, transverse horizontal and longitudinal horizontal. When the source
and the receivers were below the thermocline, both the vertical and longitudinal horizontal coherence lengths in units of
wavelength increased with increasing range and frequency. When the source was within the thermocline, the transverse horizontal
coherence length in units of wavelength decreased with frequency and exhibited weak range dependence.
The text was submitted by the authors in English. 相似文献
19.
Summary The diffraction of a spherical acoustic wave from the juncture of pressure release (soft) and locally reacting (absorbing)
half-planes in a fluid moving at subsonic velocity is examined. This consideration is important because the point sources
are regarded as better substitutes for real sources than line sources/plane waves. The integral representation of the field
is obtained using integral transforms and the Wiener-Hopf technique. The factorization of the kernel function in the Wiener-Hopf
functional equation is accomplished. The analytic solution of the integrals is obtained by employing asymptotic methods and
the far field is presented. The effect of the Mach number is shown explicitly on the diffracted field. 相似文献
20.
Ghada M. Sami 《Czechoslovak Journal of Physics》2004,54(3):339-348
The transient electromagnetic field, in the frequency domain, on a two-layered conducting earth is reexamined when the usually
neglected magnetic permeability contrast is considered. It is shown that for two-layered earth model, where the upper is permeable,
the electromagnetic induction response is modified over the nonpermeable case. It is obtained as a summation of waveguide
modes plus contributions from branch-cuts in the complex plane of the longitudinal wave number. The results from this paper
can be used to evaluate numerical solution of other more complicated forward modeling algorithms. It can also be used in developing
fast and simple interpretation tools, which can deliver quick estimation of the earth structure at the field. 相似文献