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1.
Effects of Substrate Temperature on Helium Content and Microstructure of Nanocrystalline Titanium Films 下载免费PDF全文
Helium-charged nanocrystalline titanium films have been deposited by HeAr magnetron co-sputtering. The effects of substrate temperature on the helium content and microstructure of the nanocrystalline titanium films have been studied. The results indicate that helium atoms with a high concentration are evenly incorporated in the deposited titanium films. When the substrate temperature increases from 60℃ to 350℃ while the other deposition'parameters are fixed, the helium content decreases gradually from 38.6 at.% to 9.2at.%, which proves that nanocrystalline Ti films have a great helium storage capacity. The 20 angle of the Bragg peak of (002) crystal planes of the He-charged Ti film shifts to a lower angle and that of (100) crystal plane is unchanged as compared with that of the pure Ti film, which indicates that the lattice parameter c increases and a keeps at the primitive value. The grain refining and helium damage result in the diffraction peak broadening. 相似文献
2.
The Gibbs-Thomson effect modifies the pressure and temperature at which clathrates occur, hence altering the depth at which they occur in the seabed. Nuclear magnetic resonance (NMR) measurements as a function of temperature are being conducted for water/ice/hydrate systems in a range of pore geometries, including templated SBA-15 silicas, controlled pore glasses and sol-gel silicas. Rotator-phase plastic ice is shown to be present in confined geometry, and bulk tetrahydrofuran hydrate is also shown to probably have a rotator phase. A novel NMR cryoporometry protocol, which probes both melting and freezing events while avoiding the usual problem of supercooling for the freezing event, has been developed. This enables a detailed probing of the system for a given pore size and geometry and the exploration of differences between hydrate formation and dissociation processes inside pores. These process differences have an important effect on the environment, as they impact on the ability of a marine hydrate system to re-form once warmed above a critical temperature. Ab initio quantum-mechanical molecular dynamics calculations are also being employed to probe the dynamics of liquids in pores at nanometric dimensions. 相似文献
3.
M. Keil T. Kolling K. Bergmann W. Meyer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(1):55-64
The process of dissociative attachment (DA) of low-energy electrons ) to vibrationally excited sodium dimer molecules is studied with high electron energy resolution () in a supersonic molecular beam. A novel photoelectron source, based on two-step photoionization of the sodium atoms in the
beam, may deliver a current of up to 1 nA and has been used with a current of typically 0.2 nA in this experiment. The energy
dependence of the rate of sodium anion formation is determined by ion detection based on a time-of-flight analysis. The molecules
are selectively excited to levels using the technique of coherent population transfer by delayed pulses (STIRAP). The comparison of the experimental data with
recent resonance model calculations based on improved potential curves reveals generally good agreement for levels v
”>12. For some distinct differences between theoretical and experimental results persist.
Received: 21 November 1998 / Received in final form: 7 April 1999 相似文献
4.
A. Chernomoretz C. O. Dorso 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):197-202
In this communication we analyze the behavior of excited
drops that undergo fragmentation. We focus our attention on two
scenarios: in the first one the system is free to expand, while
in the second one it is confined inside a spherical volume. It
is shown that the caloric curve of free expanding systems does
not display a vapor branch. In the case of constrained ones,
they behave as undergoing a first order phase transition at low
densities while as a second order one at high densities. The
transition from liquid-like to vapor-like behavior is signaled
both by the caloric curves and thermal response functions. 相似文献
5.
Flat Supercontinuum Generation at 1550 nm in a Dispersion-Flattened Microstructure Fibre Using Picosecond Pulse 下载免费PDF全文
The generation of a flat supercontinuum of over 80nm in the 1550nm region by injecting 1.6ps 10 GHz repetition rate optical pulses into an 80-m-long dispersion-flattened microstructure fibre is demonstrated. The fibre has small normal dispersion with a variation smaller than 1.5 (ps·nm^-1·km^-1) between 1500 and 1650nm. The generated supercontinuum ranging from 1513 to 1591 nm has the flatness of ±1.5 dB and it is not so flat in the range of several nanometres around the pump wavelength 1552nm. Numerical simulation is also used to study the effect of optical loss, fibre parameters and pumping conditions on supercontinuum generation in the dispersion-flattened microstructure fibre, and can be used for further optimization to generate flat broad spectra. 相似文献
6.
Vapour-to-Liquid Nucleation in Associating Lennard-Jones Fluids with Multiple Association Sites 下载免费PDF全文
The excess Helmholtz free energy functional for associating Lennard-Jones (L J) fluid is formulated in terms of a weighted density approximation for short-ranged interactions and a Weeks-Chandler-Andersen approximation for long-range attraction. Within the framework of density functional theory, phase equilibria, vapour-liquid surface tension and vapour-liquid nucleation properties including the density profile, work of formation, excess number of particles and critical supersaturation are investigated for associating LJ fluids with different numbers of association sites (M =1,2, 3, 4) per particle. The influences of association energy and association sites on phase equilibria, surface tension and vapour-liquid nucleation properties are discussed. 相似文献
7.
A. Makhoute D. Khalil 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(1):77-82
We study electron-atom scattering in the presence of a
laser field with elliptic polarization. We discuss the dependence
of the differential cross sections for the cases of circular and
linear polarizations as a function of scattering angle.
Interesting typical signatures of the phase between the two
components of the circular polarization of the laser field appear
in the differential cross section. 相似文献
8.
S.P. Purohit Anoop K. Jain K.C. Mathur 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,2(1):41-44
Within the framework of the rotating wave approximation the elastic scattering of electrons by metastable 2s state of hydrogen
atoms is studied in the presence of a resonant laser field. The frequency of the circularly polarized laser field is chosen
to match the 2s-3p transition frequency in the hydrogen atom. Variation of the cross section with laser intensity and with incident electron energy (50-150 eV) is investigated.
Received: 18 July 1997 / Received in final form: 5 December 1997 / Accepted: 19 January 1998 相似文献
9.
The influence of defect-core on the birefringence and confinement losses of rectangular-lattice photonic crystal fibers are investigated numerically by applying the multipole method. Numerical results illustrate that the birefringence in such fibers is determined not only by the arrangement of air holes in the cladding but also the shape of the core. It is found that asymmetry of the core represented by its rectangular shape implies a higher effective index of the mode that is parallel with the longer side of the rectangle, whereas the anisotropic rectangular-lattice cladding gives rise to just the opposite effect and thus the resulting birefringence can be controlled by a proper combinations of both mechanisms. In particular, effect of the asymmetry of the core on the birefringence is dominant for shorter wavelength. Increased birefringence and reduced confinement loss can be achieved, if we form the core by the omission of several air holes in a row to reduce its negative effect on the birefringence. On the other hand, when asymmetry is increased in the other direction, a negative birefringence at shorter wavelength can be achieved. This occurs due to the fact that asymmetry of the core at higher frequencies overcomes the effect of the asymmetric cladding. As a result, its possible to achieve zero birefringence in anisotropic cladding photonic crystal fiber with an asymmetric core. 相似文献
10.
S. O. Konorov A. A. Ivanov M. V. Alfimov A. M. Zheltikov 《Applied physics. B, Lasers and optics》2005,81(2-3):219-223
Femtosecond Cr: forsterite laser pulses coupled into small-diameter birefringent channel waveguides off the central core of a photonic-crystal fiber are shown to generate multiple narrowband spectral peaks within the 380–460 nm wavelength region through multimode-phase-matched third-harmonic generation. Some of these peaks are shifted by tens of terahertz from the tripled frequency of the pump field, dictated by standard energy conservation for third-harmonic generation in monochromatic fields. The spectral contents of the third-harmonic signal generated in such a regime are controlled by changing polarization and the intensity of the input pump field. 相似文献