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31.
Recent advances in interpreting the most accurate-to-date measurement of atomic parity violation in Cs are reviewed. The inferred
nuclear weak charge, Q
W( ^133Cs ) = - 72.65(28)expt(36)theor , agrees with the prediction of the standard model at 1σ level. Further improved interpretation is limited by an accuracy
of solving the basic correlation problem of the atomic structure. We report on our progress in solving this problem within
the relativistic coupled-cluster formalism. We include single, double and triple electronic excitations in the coupled-cluster
expansion. Numerical results for energies, electric-dipole matrix elements, and hyperfine-structure constants of Cs are presented. 相似文献
32.
The spinel NiCo2O4 nanofibers with diameters of 50-100 nm were prepared by high temperature calcinations of a simple inorganic-polymer composite fibers, which were obtained by electrospinning of the PVA/cobalt acetate/nickel acetate composite precursor. The crystallinity, purity, and surface morphology of the as-prepared NiCo2O4 nanofibers were investigated by XRD, FT-IR, SEM, respectively. 相似文献
33.
X.S. Peng X.F. Wang J. Zhang Y.W. Wang S.H. Sun G.W. Meng L.D. Zhang 《Applied Physics A: Materials Science & Processing》2002,74(6):831-833
High-yield synthesis of amorphous silicon oxide nanoropes (SiONRs) was achieved by using simple evaporation and oxidation
of Si. Transmission electron microscopy observations show that the amorphous SiONRs have a length of up to several hundreds
of micrometers and a diameter of 20 to 40 nm. Energy-dispersive X-ray analysis reveals that the SiONRs consist of Si and O
elements in an atomic ratio of approximately 1:1.2. The formation process of the SiONRs is closely related to a vapor–solid
method. The SiONRs emit blue light at energies of 2.53 and 3.0 eV.
Received: 2 January 2002 / Accepted: 7 January 2002 / Published online: 20 March 2002 相似文献
34.
J.H. Chen Z.P. Huang D.Z. Wang S.X. Yang J.G. Wen Z.F. Ren 《Applied Physics A: Materials Science & Processing》2001,73(2):129-131
Polypyrrole/carbon nanotube nanoscale composites were successfully fabricated by electrochemical deposition of polypyrrole
over each of the carbon nanotubes in well-aligned large arrays. The thickness of the polypyrrole coating can be easily controlled
by the value of the film-formation charge. For both thin (low film-formation charge) and thick (high film-formation charge)
films, the polypyrrole coating on the surface of each nanotube is very uniform throughout the entire length, as observed by
transmission electron microscopy.
Received: 2 May 2001 / Accepted: 4 May 2001 / Published online: 20 June 2001 相似文献
35.
Z.J. Li H.J. Li X.L. Chen A.L. Meng K.Z. Li Y.P. Xu L. Dai 《Applied Physics A: Materials Science & Processing》2003,76(4):637-640
Large quantities of high-purity crystalline β-SiC nanowires have been synthesized at relatively low temperature via a new
simple method, the chemical-vapor-reaction approach, in a home-made graphite reaction cell. A mixture of milled Si and SiC
powders and C3H6 were employed as the starting materials. The results show that the nanowires with diameters of about 10–35 nm are single
crystalline β-SiCwithout any wrapping of amorphous material, and the nanowire axes lie along the 〈111〉 direction. Some unique
properties are found in the Raman scattering from the β-SiC nanowires, which are different from previous observations of β-SiC
materials. A possible growth mechanism for the β-SiC nanowires is proposed.
Received: 27 August 2002 / Accepted: 28 August 2002 / Published online: 4 December 2002
RID="*"
ID="*"Corresponding author. Fax: +86-29/8491-000, E-mail: zjli-sohu@sohu.com 相似文献
36.
The inner structure of Rh/Ys,a novel high efficiency supported catalyst,and the spreading of Rh on the Ys surface were analyzed through electron transmission microscopy and scanning tunnel microscopy.The relationship between the distribution of Rh over the support and the preparation temperature of th catalyst was determined.The formation of Rh-C bond was confirmed by XPS and far-IR spectra.The loss of Rh from the surface of the support and the catalytic activity under different preparation conditions have been compared.The internal factors for the high activity and high stability of the novel Rh/Ys catalyst have been discussed. 相似文献
37.
E. Jahier J. Guéna Ph. Jacquier M. Lintz M.A. Bouchiat 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,17(2):221-229
We demonstrate the production of an electric field inside a high temperature cesium vapor cell with external electrodes. This external control of the electric field, which is not possible with a glass cell in presence of a cesium
vapor, is achieved using a cell made of sapphire, and is of particular interest for our ongoing Parity Violation experiment.
We describe the main components and the implementation on the set-up, including the pulsed high voltage generator. With pulse
duration not exceeding 200 ns the system provides a reversible longitudinal E-field of up to 2 kV/cm in the vapor at a density of ∼ 2×1014 at/cm3 without discharge. Atomic signals attest the application of the electric field in the cell, with the predicted value. Further
improvements obtained with sapphire cells are also presented.
Received 15 September 2000 相似文献
38.
Preparation and characterization of nano-sized Ag/PVP composites for optical applications 总被引:2,自引:0,他引:2
G. Carotenuto G.P. Pepe L. Nicolais 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(1):11-17
A modification of the polyol process has enabled the direct synthesis of nm-sized Ag particles with narrow size distribution
and controlled average dimension embedded in a polymeric matrix. Dispersion of colloidal silver was obtained by reduction
of silver nitrate in ethylene-glycol in the presence of a polymeric protective agent (i.e., poly(N-vinylpyrrolidone)) and ultrasounds. The final particle size was controlled by removing the colloid from the reactive
mixture by addition of acetone. The very strong plasmon resonance peak at 410 nm and a feature at 350 nm in the UV-visible
spectra are a clear consequence of the nano-size of dilute Ag particles. The proposed process offers the possibility to effectively
use these synthesised materials for the production of colour filters for advanced optical devices.
Received 10 November 1999 相似文献
39.
T. Gasenzer O. Nachtmann 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(1):95-110
In this article we study effects of parity nonconservation in atomic dysprosium, where one has a pair of nearly degenerate
levels of opposite parity. We consider the time evolution of this two-level system within oscillatory electric and magnetic
fields. These are chosen to have a periodical structure with the same period, such that a Floquet matrix describes the time
evolution of the quantum states. We show that, if the states are unstable, the eigenvalues of the Floquet matrix may have
contributions proportional to the square root of the parity violating interaction matrix element while they are almost degenerate in their parity even part. This leads to beat frequencies proportional to which are expected to be larger by several orders of magnitude compared to ordinary P-violating contributions which are of
order . However, for the simple field configurations we considered, it still seems to be difficult to observe these P-violating
beat effects, since the states decay too fast. On the other hand, we found that, within only a few Floquet cycles, very large
parity violating asymmetries with respect to experimental setups of opposite chirality may be obtained. The electric and magnetic
fields as well as the time intervals necessary for this are in an experimentally accessible range. For statistically significant
effects beyond one standard deviation a number of about 107 atoms is required. Our ideas may be applied directly to other 2-level atomic systems and different field configurations.
We hope that these ideas will stimulate experimental work in this direction.
Received 16 September 1999 and Received in final form 10 March 2000 相似文献
40.
A facile one-pot solvothermal route has been developed for the synthesis of tubular luminescent polymeric networks [(C3N3)2(NH)3]n, structurally related to the proposed g-C3N4. XRD patterns showed a characteristic 002 basal plane diffractions, indicating an interlayer d spacing of 3.23 Å. XPS spectra show that the C1s and N1s have a symmetric peak and an asymmetric peak at 288.10 and 399.00 eV, respectively. The bulk composition C6N8.9H4.5 determined by elemental analysis is comparable to the calculated value C6N9H3 for this proposed polymer. FTIR spectra indicated the presence of s-triazine ring, which was further supported by the luminescent and UV-vis absorption characteristics probably depending on π→π* electronic transition. The tubular structure has been studied by TEM, SAED, and HREM. 相似文献