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排序方式: 共有527条查询结果,搜索用时 93 毫秒
21.
A novel metal-organic complex [La(o-NCP)3]n(o-HNCP = 2-(2-carboxyphenyl)imidazo(4,5- f)(1,10)-phenanthroline) has been hydrothermally synthesized and characterized by elemental analysis, infrared analysis and X-ray single-crystal diffraction. The complex crystallizes in triclinic, space group P1 with a = 9.898(2), b = 16.193(3), c = 16.909(3) , α = 67.68(3), β = 80.85(3), γ = 78.78(3)o, V = 2448.2(8) A3, Z = 2, Mr = 1156.9, Dc = 1.569 g/cm3, μ = 0.71073 A, F(000) = 1164, GOOF = 1.065, the final R = 0.051 and wR = 0.123 for 8539 observed reflections with I 2A(I). The complex exhibits a one-dimensional double chain structure. The adjacent chains are further connected by N–H...N hydrogen bonds which help to form a two-dimensional supramolecular architecture. Furthermore, the complex exhibits excellent thermal stability and luminescent property. 相似文献
22.
在水热条件下,以对苯二甲酸(H2bdc)和咪唑并[4,5-f][1,10]邻菲咯啉(Imphen)为配体构筑了两种配合物[Cd(bdc)(Imphen)(H2O)]n·nH2O(1)和[Zn(bdc)(Imphen)(H2O)]n·nH2O(2),并利用元素分析和X-射线单晶衍射对其结构进行了表征。结构分析表明:bdc2-在2个配合物中展示了不同的配位模式,配合物1和2都具有一维链状结构,并且都通过分子间氢键和π-π相互作用形成三维网状结构。此外,对配合物的热稳定性和发光性质也进行了研究。 相似文献
23.
E.?Tomasi-GustafssonEmail author F.?Lacroix C.?Duterte G.?I.?Gakh 《The European Physical Journal A - Hadrons and Nuclei》2005,24(3):419-430
We perform a global analysis of the experimental data of the electromagnetic nucleon form factors, in space-like and time-like regions. We give the expressions of the observables in annihilation processes, such as p + ¯↦ℓ+ + ℓ-, ℓ = e or μ, in terms of form factors. We discuss some of the phenomenological models proposed in the literature for the space-like region, and consider their analytical continuation to the time-like region. After determining the parameters through a fit on the available data, we give predictions for the observables which will be experimentally accessible with large statistics, polarized annihilation reactions 相似文献
24.
S.-H. Cho H. Kumagai K. Midorikawa 《Applied Physics A: Materials Science & Processing》2003,76(5):755-761
The time-resolved dynamics of plasma self-channeling and refractive index bulk modification in silica glasses were first observed
in situ using a high-intensity femtosecond (110 fs) Ti:sapphire laser (λp=790 nm). Plasma channeling is induced in silica glass at an irradiation higher than an input intensity of 1.5×1012 W/cm2 and photoinduces either the refractive-index modification or optical crack modification. In the domain of refractive-index
modification, the lifetime of induced plasma self-channeling was 20 ps and the structural transition time for forming the
refractive-index change was 10 ps. In the domain of optical cracks, however, the lifetime of induced plasma formation was
30 ps and the structural transition time for forming the optical cracks was 40 ps. According to electron spin resonance spectroscopic
(ESP) measurement, it was found that the defect concentration of the SiE′ center increased significantly in the refractive index modification region. A maximum value of the refractive-index change
Δn was measured to be 1.6×10-2. The intensity profile of the output beam transmitted through the refractive-index modification showed that the bulk modification
produced a permanent optical waveguide.
Received: 8 April 2002 / Accepted: 12 April 2002 / Published online: 22 November 2002
RID="*"
ID="*"Corresponding author. Fax: +81-48/462-4682, E-mail: shcho@riken.go.jp 相似文献
25.
D. Golberg P.S. Dorozhkin Y. Bando Z.-C. Dong C.C. Tang Y. Uemura N. Grobert M. Reyes-Reyes H. Terrones M. Terrones 《Applied Physics A: Materials Science & Processing》2003,76(4):499-507
Transport and field-emission properties of as-synthesized CNx and BNCx (x<0.1) multi-walled nanotubes were compared in detail. Individual ropes made of these nanotubes and macrofilms of those
were tested. Before measurements, the nanotubes were thoroughly characterized using high-resolution and energy-filtered electron
microscopy, electron diffraction and electron-energy-loss spectroscopy. Individual ropes composed of dozens of CNx nanotubes displayed well-defined metallic behavior and low resistivities of ∼10–100 kΩ or less at room temperature, whereas
those made of BNCx nanotubes exhibited semiconducting properties and high resistivities of ∼50–300 MΩ. Both types of ropes revealed good field-emission
properties with emitting currents per rope reaching ∼4 μA(CNx) and ∼2 μA (BNCx), albeit the latter ropes se- verely deteriorated during the field emission. Macrofilms made of randomly oriented CNx or BNCx nanotubes displayed low and similar turn-on fields of ∼2–3 V/μm. 3 mA/cm2 (BNCx) and 5.5 mA/cm2 (CNx) current densities were reached at 5.5 V/μm macroscopic fields. At a current density of 0.2–0.4 mA/cm2 both types of compound nanotubes exhibited equally good emission stability over tens of minutes; by contrast, on increasing
the current density to 0.2–0.4 A/cm2, only CNx films continued to emit steadily, while the field emission from BNCx nanotube films was prone to fast degradation within several tens of seconds, likely due to arcing and/or resistive heating.
Received: 29 October 2002 / Accepted: 1 November 2002 / Published online: 10 March 2003
RID="*"
ID="*"Corresponding author. Fax: +81-298/51-6280, E-mail: golberg.dmitri@nims.go.jp 相似文献
26.
E. I. Moses R. E. Bonanno C. A. Haynam R. L. Kauffman B. J. MacGowan R. W. Patterson Jr R. H. Sawicki B. M. Van Wonterghem 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(2):215-218
The National Ignition Facility (NIF) is a 192-beam laser
facility presently under construction at LLNL. When completed, NIF will be a
1.8-MJ, 500-TW ultraviolet laser system. Its missions are to obtain fusion
ignition and to perform high energy density experiments in support of the
US nuclear weapons stockpile. Four of the NIF beams have been commissioned
to demonstrate laser performance and to commission the target area including
target and beam alignment and laser timing. During this time, NIF
demonstrated on a single-beam basis that it will meet its performance goals
and demonstrated its precision and flexibility for pulse shaping, pointing,
timing and beam conditioning. It also performed four important experiments
for Inertial Confinement Fusion and High Energy Density Science. Presently,
the project is installing production hardware to complete the project in
2009 with the goal to begin ignition experiments in 2010. An integrated plan
has been developed including the NIF operations, user equipment such as
diagnostics and cryogenic target capability, and experiments and
calculations to meet this goal. This talk will provide NIF status, the plan
to complete NIF, and the path to ignition. 相似文献
27.
K. Ohno Y. Noguchi S. Ueda J. Onoe 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):137-140
Optimized three-dimensional (3D) cell structures and energy bands
of fused (peanut-shaped) C60 polymers (p55 and p66) have been
investigated using the first-principles pseudopotential approach
within the local density approximation of the density functional theory.
We found that the resulting electronic structure is either metal or
semiconductor depending on the shape of the polymer chains and
the unit cell structure. 相似文献
28.
H. Jensen J. Kröger N. Néel R. Berndt 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(3):465-469
Clusters on surfaces have been investigated with low-temperature scanning tunnelling microscopy and spectroscopy. Constant
current spectra acquired on Ag oligomers and one-dimensional chains on a Ag(111) reveal a
single resonance peak whose energy shifts towards the Fermi level with increasing cluster size. Next, controlled and reproducible
contact between a STM tip and a C60 molecule adsorbed on Cu(100) is reported. The
transition from tunnelling to contact is discussed in terms of local heating of the tip-molecule junction. 相似文献
29.
D. Khalil A. Makhoute A. Maquet G. Rahali M. Zitane 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):287-295
The dynamics of laser-assisted elastic collisions in
helium is studied using the second-order Born approximation.
Detailed calculations of the scattering amplitudes are performed
by using the Sturmian basis expansion. Differential cross sections
for elastic scattering with the net absorption/emission of up to
two photons are calculated for collision energies of 5 eV, 10 eV,
and 20 eV. We discuss the influence of the low-energy electrons on
the differential cross section (DCS) as a function of the
scattering angle for selected choices of the laser frequency and
the number of photons exchanged between the external field and
electron-helium system. 相似文献
30.
A. Tanaka R. Saito T. Kamikake M. Imamura H. Yasuda 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):229-232
We have performed the optical and photoelectron
spectroscopic studies of alkyl-passivated Si nanoparticles synthesized by a
solution route. The alkyl-passivated Si nanoparticle with mean diameter less
than about 2 nm exhibits a strong ultraviolet-blue photoluminescence.
Furthermore, we have directly investigated their electronic structures in
the vicinity of Fermi level by means of valence-band photoemission
measurements using synchrotron radiation. From these results, the detailed
optical properties and electronic structures of alkyl-passivated Si
nanoparticles are discussed. 相似文献