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1.
L.M. Schmitt 《Applied Physics A: Materials Science & Processing》1999,68(5):553-558
We discuss the transmission coefficient τd in non-repetitive, one-dimensional, rectangular double-barrier structures without simplifications such as strongly attenuating
barriers, strong localization, or overall constant effective tunneling mass of the electron. For resonance τd=1, we obtain two non-approximative conditions which require different resonance energies of the tunneling electron than previously
reported in the literature. In fact, the resonance peaks are shifted to higher energy levels in the order of the width of
the peaks due to the effect of non-constant tunneling mass. We investigate the dependence of the resonance condition and the
shape of the resonance peaks in regard to perturbation of the electron energy, the gap width as well as the barrier width
and height. Resonance is stable for variation of the barrier width but sensitive for variation of the barrier height and the
gap width.
Received: 9 December 1998 / Accepted: 5 January 1999 / Published online: 31 March 1999 相似文献
2.
We study zero-temperature, stochastic Ising models σ
t
on Z
d
with (disordered) nearest-neighbor couplings independently chosen from a distribution μ on R and an initial spin configuration chosen uniformly at random. Given d, call μ type ℐ (resp., type ℱ) if, for every
x in Z
d
, σ
x
t
flips infinitely (resp., only finitely) many times as t→∞ (with probability one) – or else mixed type ℳ. Models of type ℒ and ℳ exhibit a zero-temperature version of “local non-equilibration”.
For d=1, all types occur and the type of any μ is easy to determine. The main result of this paper is a proof that for d=2, ±J models (where μ=αδ
J
+(1-α)δ-
J
) are type ℳ, unlike homogeneous models (type ℐ) or continuous (finite mean) μ's (type ℳ). We also prove that all other noncontinuous
disordered systems are type ℳ for any d≥ 2. The ±J proof is noteworthy in that it is much less “local” than the other (simpler) proof. Homogeneous and ±J models for d≥ 3 remain an open problem.
Received: 3 November 1999 / Accepted: 10 April 2000 相似文献
3.
J. Söding D. Guéry-Odelin P. Desbiolles F. Chevy H. Inamori J. Dalibard 《Applied physics. B, Lasers and optics》1999,69(4):257-261
We have measured the three-body decay of a Bose–Einstein condensate of rubidium (87Rb) atoms prepared in the doubly polarized ground state F=m
F
=2. Our data are taken for a peak atomic density in the condensate varying between 2×1014 cm-3 at initial time and 7×1013 cm-3, 16 s later. Taking into account the influence of the uncondensed atoms on the decay of the condensate, we deduce a rate
constant for condensed atoms L=1.8 (±0.5) ×10-29 cm6 s-1. For these densities we did not find a significant contribution of two-body processes such as spin dipole relaxation.
Received: 24 November 1998 / Revised version: 26 June 1999 / Published online: 8 September 1999 相似文献
4.
Structural properties of silver nanoparticle agglomerates based on transmission electron microscopy: relationship to particle mobility analysis 总被引:1,自引:1,他引:0
Weon Gyu Shin Jing Wang Michael Mertler Bernd Sachweh Heinz Fissan David Y. H. Pui 《Journal of nanoparticle research》2009,11(1):163-173
In this work, the structural properties of silver nanoparticle agglomerates generated using condensation and evaporation method
in an electric tube furnace followed by a coagulation process are analyzed using Transmission Electron Microscopy (TEM). Agglomerates
with mobility diameters of 80, 120, and 150 nm are sampled using the electrostatic method and then imaged by TEM. The primary
particle diameter of silver agglomerates was 13.8 nm with a standard deviation of 2.5 nm. We obtained the relationship between
the projected area equivalent diameter (d
pa) and the mobility diameter (d
m), i.e., d
pa = 0.92 ± 0.03 d
m for particles from 80 to 150 nm. We obtained fractal dimensions of silver agglomerates using three different methods: (1)
D
f = 1.84 ± 0.03, 1.75 ± 0.06, and 1.74 ± 0.03 for d
m = 80, 120, and 150 nm, respectively from projected TEM images using a box counting algorithm; (2) fractal dimension (D
fL) = 1.47 based on maximum projected length from projected TEM images using an empirical equation proposed by Koylu et al.
(1995) Combust Flame 100:621–633; and (3) mass fractal-like dimension (D
fm) = 1.71 theoretically derived from the mobility analysis proposed by Lall and Friedlander (2006) J Aerosol Sci 37:260–271.
We also compared the number of primary particles in agglomerate and found that the number of primary particles obtained from
the projected surface area using an empirical equation proposed by Koylu et al. (1995) Combust Flame 100:621–633 is larger
than that from using the relationship, d
pa = 0.92 ± 0.03 d
m or from using the mobility analysis. 相似文献
5.
Raymond K. Sheline C. F. Liang P. Paris P. Alexa J. Kvasil 《Czechoslovak Journal of Physics》2004,54(7):721-738
Minor changes in the assignments of gamma rays following the alpha decay of228Pa in two previous studies make possible a reinterpretation of224Ac into two alternative level schemes. The resulting level structures arise from the reflection asymmetric configurations
π3/2±(0.0 −0.3)−ν3/2±(−0.1 0.6), π5/2±(0.0 −0.2)±ν3/2±(−0.1 0.6) and π5/2±(0.0 −0.2)±ν1/2±(0.2 −0.1 3) which give rise to eitherK=0± or 1±,K=4±,K=2± andK=3± parity doublet bands. The bands with appreciable band structure, namelyK=0± or 1± andK=3±, have average parity doublet splittings of 11.0 and 5.8 keV respectively. These are extremely small values and suggest that224Ac is the most octupole deformed nucleus studied thus far. A method of calculating the parity doublet splitting in odd-odd
nuclei is suggested and tested for224Ac. It seems to work remarkably well. The systematics of the hindrance factors for the bands with extended band structures
confirm their interpretations as band structures. Finally, the two alternative level schemes are analyzed in the framework
of the axially-symmetric rigid rotor model including the Coriolis interaction. 相似文献
6.
S.V. Golovkin A.P. Kozhevnikov V.P. Kubarovsky V.F. Kurshetsov L.G. Landsberg V.V. Molchanov V.A. Mukhin S.V. Petrenko V.A. Senko D.V. Vavilov V.A. Victorov V.Z. Kolganov G.S. Lomkatsi A.F. Nilov V.T. Smolyankin 《The European Physical Journal A - Hadrons and Nuclei》1999,5(4):409-416
New data for the diffractive reaction p+N→ [Σ0
K
+] +N at E
p= 70 GeV were obtained with partially upgraded SPHINX setup. The data are in a good agreement with the results of our previous
study of this reaction. In the mass spectrum M(Σ0
K
+) a structure at the threshold region with a mass ∼1810 MeV and a distinct X(2000) peak with M= 1989 ± 6 MeV and γ= 91 ± 20 MeV are observed. Unusual features of the massive X(2000) state (narrow decay width, anomalously
large branching ratio for the decay channel with strange particle emission) make it a serious candidate for cryptoexotic pentaquark
baryon with hidden strangeness |qqqsˉs>. We also present new results on the narrow threshold structure X(1810) with M= 1807 ± 7 MeV and γ= 62 ± 19 MeV which is produced in the region of very small P
2
T < 0.01 GeV2. The possibility of the Coulomb production mechanism for X(1810) is discussed.
Received: 28 April 1999 相似文献
7.
R. V. Kuz’menko A. V. Ganzha O. V. Bochurova É. P. Domashevskaya J. Schreiber S. Hildebrandt S. Mo E. Peiner 《Physics of the Solid State》1999,41(4):654-659
A study is reported of the structure of photoreflectance (PR) spectra in the vicinity of the E
0 transition from thin (d=1–5 μm) n-GaAs and n-InP films (n=1016–1017 cm−3) grown epitaxially on Si(001) substrates. A quantitative analysis of the spectra involving multi-component fitting shows
that the electronic optical transition from the {3/2;±1/2} subband provides a dominant contribution to the intermediate-field
electromodulation component in both systems. The splitting observed in the GaAS/Si PR spectra near the main peak are accounted
for not by the strain-induced valence-band splitting but rather by a spectral superposition of the intermediate-field component
due to the {3/2;±1/2} subband with a low-energy excitonic component. The analytically established transition energy E
0
3/2;±1/2
is used to calculate biaxial strains in epitaxial films.
Fiz. Tverd. Tela (St. Petersburg) 41, 725–731 (April 1999) 相似文献
8.
9.
V. M. Matyushin 《Technical Physics》1999,44(7):804-806
An investigation is made of the diffusion of gold in germanium under the influence of the energy released by the recombination
of hydrogen atoms to form molecules. Crystals of n-type germanium with gold films (d=1×10−7 m) are exposed to atomic hydrogen for various times (up to 104 s) at temperatures close to room temperature. The diffusion of gold in the germanium is analyzed by laser mass spectrometry,
and also by measuring the surface resistance, the minority carrier lifetime, and the infrared transmission spectra. Mechanisms
are proposed for the stimulation of heterodiffusion and accompanying processes.
Zh. Tekh. Fiz. 69, 73–76 (July 1999) 相似文献
10.
Yu.N. Lobach A.D. Efimov A.A. Pasternak 《The European Physical Journal A - Hadrons and Nuclei》1999,6(2):131-140
Lifetimes of excited states in 110Cd have been measured by the Doppler shift attenuation method in the reaction (α,2nγ) at E
α= 25 MeV. Lifetime values for 8 states and lifetime limits for 3 states were obtained. The band structures of 110Cd have been interpreted in terms of a modified version of the interacting boson model (IBM + 2 q.p.). The calculations explain
well the excitation energies and electromagnetic transition probabilities up to J
π= 16+, except for the 10+
1 state. The structural features are discussed in terms of collective and two quasiparticle excitations.
Received: 20 March 1999 / Revised version: 28 May 1999 相似文献
11.
W. Cassing L. Jarczyk B. Kamys P. Kulessa H. Ohm K. Pysz Z. Rudy O.W.B. Schult H. Ströher 《The European Physical Journal A - Hadrons and Nuclei》2003,16(4):549-561
The lifetime of the Λ-hyperon in heavy hypernuclei measured in proton-Au, -Bi and -U collisions by the COSY-13 Collaboration
at COSY-Jülich has been analyzed to yield τΛ = (145±11) ps. This value for τΛ is compatible with the lifetime extracted from antiproton annihilation on Bi and U targets, albeit much more accurate. Theoretical
models based on the meson exchange picture and assuming the validity of the phenomenological ΔI = 1/2 rule predict the lifetime of heavy hypernuclei to be significantly larger (2-3 standard deviations). Such large differences
indicate that at least one of the assumptions in these models is not fulfilled. A much better reproduction of the lifetimes
of heavy hypernuclei is achieved in the phase space model, if the ΔI = 1/2 rule is discarded in the nonmesonic Λ decay.
Received: 8 August 2002 / Accepted: 20 December 2002 / Published online: 25 March 2003
RID="a"
ID="a"e-mail: h.stroeher@fz-juelich.de
Communicated by Th. Walcher 相似文献
12.
J. P. Xu X. Zou C. X. Li P. T. Lai C. L. Chan 《Applied Physics A: Materials Science & Processing》2009,94(2):419-422
Reactive cosputtering is employed to prepare high-permittivity HfTiO gate dielectric on n-Ge substrate. Effects of Ge-surface
pretreatment on the interface and gate leakage properties of the dielectric are investigated. Excellent performances of Al/HfTiO/GeO
x
N
y
/n-Ge MOS capacitor with wet–NO surface pretreatment have been achieved with a interface-state density of 2.1×1011 eV−1 cm−2, equivalent oxide charge of −7.67×1011 cm−2 and gate leakage current density of 4.97×10−5 A/cm2 at V
g
=1 V. 相似文献
13.
Hungchong Kim 《The European Physical Journal A - Hadrons and Nuclei》2000,7(1):121-125
Within the conventional QCD sum rules, we calculate the πNN coupling constant, g
πN, beyond the chiral limit using two-point correlation function with a pion. For this purpose, we consider the Dirac structure,
iγ5, at m
π
2 order in the expansion of the correlator in terms of the pion momentum. For a consistent treatment of the sum rule, we include
the linear terms in quark mass as they constitute the same chiral order as m
π
2. In this sum rule, we obtain g
πN= 13.3 ± 1.2, which is very close to the empirical πNN coupling. This demonstrates that going beyond the chiral limit is crucial in determining the coupling.
Received: 8 July 1999 / Revised version: 20 August 1999 相似文献
14.
C. Schönenberger A. Bachtold C. Strunk J.-P. Salvetat L. Forró 《Applied Physics A: Materials Science & Processing》1999,69(3):283-295
We report equilibrium electric resistance R and tunneling spectroscopy (dI/dV)measurements obtained on single multi-wall nanotubes
contacted by four metallic Au fingers from above. At low temperature quantum interference phenomena dominate the magnetoresistance.
The phase-coherence (lφ)and elastic-scattering lengths (le)are deduced. Because le is of order of the circumference of the nanotubes, transport is quasi-ballistic. This result is supported by a dI/dV spectrum
which is in good agreement with the density of states (DOS) due to the one-dimensional subbands expected for a perfect single-wall
tube. As a function of temperature T the resistance increases on decreasing T and saturates at ≈1–10 Kfor all measured nanotubes.
R(T) cannot be related to the energy-dependent DOS of graphene but is mainly caused by interaction and interference effects.
On a relatively small voltage scale of the order ≈10 meV, a pseudogap is observed in dI/dV which agrees with Luttinger-liquid
theories for nanotubes. Because we have used quantum diffusion based on Fermi-liquid as well as Luttinger-liquid theory in
trying to understand our results, a large fraction of this paper is devoted to a careful discussion of all our results.
Received: 17 May 1999 / Accepted: 18 May 1999 / Published online: 4 August 1999 相似文献
15.
ALEPH Collaboration D. Buskulic D. Casper I. De Bonis D. Decamp P. Ghez C. Goy J. -P. Lees A. Lucotte M. -N. Minard et al. 《Zeitschrift fur Physik C Particles and Fields》1995,69(1):379-392
A data sample of about 3.0 million hadronicZ decays collected by the ALEPH experiment at LEP in the years 1991 through 1994 is used to make an inclusive selection of
B hadron events. In this event sample 4227±140±252B* mesons in the decayB*→Bγ and 1944±108±161B**
u,d
mesons decaying into a B meson and a charged pion are reconstructed. Here and in the followingB**
u,d
denotes the eightL=1(bū) and (bd) states and their charge conjugate.
For the well establishedB* meson the following quantities are obtained:ΔM=M
B*−MB=(45.30±0.35±0.87) MeV/c2 andN
B*/(N
B+N
B*)=(77.1±2.6±7.0)%. The angular distribution of the photons in theB* rest frame is used to measure the relative contribution of longitudinalB* polarization states to beσ
L/(σ
L+σ
T)=(33±6±5)%. 相似文献
16.
T. Shizuma K. Furuno K. Hata H. Ishiyama T. Jumatsu M. Kato T. Komatsubara K. Matsuura Y. Sasaki K. Uchiyama T. Hayakawa 《The European Physical Journal A - Hadrons and Nuclei》1998,1(3):245-246
High-spin states in 183Os have been studied by means of in-beam γ-ray spectroscopy. Two isomers with I
π= ((43/2)−) and (43/2)+ have been identified at excitation energies of E
x
= 5.068 and 5.168 MeV. The half-lives are determined as T
1/2= 27 ± 3 and 24 ± 2 ns.
Received: 22 December 1997 相似文献
17.
18.
C.H. Shek T.S. Gu G.M. Lin J.K.L. Lai 《Applied Physics A: Materials Science & Processing》1998,66(4):413-418
2 O3 and nanocrystalline Al2O3 specimens. The short-lifetime (170±20 ps), intermediate-lifetime (410±20 ps) and long-lifetime components correspond to three
different kinds of defects: monovacancy-like free volumes, microvoids, and larger voids. The appearance of lifetimes in the
range 1–5 ns indicates the formation of positronium. The influence of thermal annealing from 873 K to 1373 K on positron lifetime
parameters was also analyzed. The components with lifetimes τ1=170 ps and τ2=410 ps persisted even after the grains had grown to 100 nm in size, while the long-lifetime component declined significantly
when grain sizes exceeded 10 nm. The interface characteristics of polycrystalline nano-Al2O3 prepared by the two methods were compared by analyzing the variations of the positron-lifetime parameters with grain growth.
Received: 1 April 1997/Accepted: 13 August 1997 相似文献
19.
J. Mrázek M. Honusek A. Špalek J. Bielčík J. Slívová J. Adam A.A. Pasternak 《The European Physical Journal A - Hadrons and Nuclei》1999,5(4):399-408
The results of in-beam investigations of excited states of 99Ru using the 98Mo(α,3n) reaction are presented. Angular distributions of γ–rays and γ–γ coincidences have been measured. Excited states have
been identified up to an energy of E = 5603 keV and spin of Iπ= 31/2−. Mean lifetimes τ have been determined using the DSA method for eleven levels. Aligned angular momenta are discussed and
the probable (νh
11/2) origin of a backbending at frequency about 0.5 MeV was confirmed. The possible role of (νd
5/2) alignment at frequencies above 0.5 MeV was pointed out.
Received: 13 January 1999 / Revised version: 26 March 1999 相似文献
20.
R.A. Gunasekaran J.D. Pedarnig M. Dinescu 《Applied Physics A: Materials Science & Processing》1999,69(6):621-624
A parametric study of the growth of La0.5Sr0.5CoO3 (LSCO) thin films on (100) MgO substrates by pulsed-laser deposition (PLD) is reported. Films are grown under a wide range
of substrate temperature (450–800 °C), oxygen pressure (0.1–0.9 mbar), and incident laser fluence (0.8–2.6 J/cm2). The optimum ranges of temperature, oxygen pressure, and laser fluence to produce c-axis oriented films with smooth surface morphology and high metallic conductivity are identified. Films deposited at low
temperature (500 °C) and post-annealed in situ at higher temperatures (600–800 °C) are also investigated with respect to their
structure, surface morphology, and electrical conductivity.
Received: 20 November 1998 / Accepted: 6 July 1999 / Published online: 21 October 1999 相似文献