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971.
H. Nienhaus V. van Elsbergen W. Mönch 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(2):179-182
Si-terminated 3C-SiC(001) surfaces with () and ()reconstructions were investigated by high-resolution electron energy-loss spectroscopy (HREELS), low-energy electron diffraction
(LEED) and Auger electron spectroscopy. The surfaces were prepared by subsequent annealing steps after cleaning by heating
in a Si flux. At ()-reconstructed surfaces, the HREELS intensity increases while the widths of the loss lines decrease with proceeding preparation.
Eventually, weak loss structures at 380 and 700 cm-1 are detected besides the strong Fuchs-Kliewer phonon loss peaks. They are attributed to surface-localized vibrations, i.e., to stretching modes of on-top Si dimers and of C-Si-C groups, respectively. The weak features vanish after exposure to atomic
deuterium, but reappear after subsequent annealing. At () reconstructed surfaces the HREELS lines are broadened and no surface-localized modes were resolved.
Received 18 January 1999 相似文献
972.
The collective mode spectrum of the magnetized ionic mixture consisting ofs components is studied by starting from the microscopic balance equations and the fluctuation formulas for the microscopic densities. Apart from a heat mode ands-1 diffusion modes with frequencies of second order in the wavenumber, four modes with complex finite frequencies for vanishing wavenumber are found. If the mixture consist of particles with equal ratios of charge and mass, these four modes become similar to the gyroplasmon modes of the magnetized one-component plasma of which the frequencies are real in lowest order in the wavenumber. Green-Kubo relations are derived for the transport coefficients which appear in the frequencies of the heat mode and the diffusion modes. The long-time behavior of the integrands of the Green-Kubo expressions is evaluated with the help of mode-coupling theory. The static transport coefficients are found to be finite unless the mixture consists of species with equal ratios of charge and mass. It is concluded that the presence of species with different charge-mass ratios is essential for the validity of magnetohydrodynamics for an ionic mixture. 相似文献
973.
974.
T. Döppner S. Teuber Th. Diederich Th. Fennel P. Radcliffe J. Tiggesbäumker K. H. Meiwes-Broer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):157-160
Lead clusters are exposed to strong femtosecond light
pulses. The dependence of the recoil energy on the charge state
of the atomic ion is now investigated using a new detection
setup, i.e., a Thomson
analyser. First results show that in contrast to laser-induced
overdense plasmas at surfaces the recoil energy distribution
appears much narrower. Comparing free lead clusters with lead
clusters embedded in large helium droplets, the charging
dynamics show distinct differences on the femtosecond time
scale. In the embedded case the maximum ionization enhancement
is reached earlier. 相似文献
975.
M. Cozzini 《Pramana》2006,66(1):31-42
The collective modes of a rotating Bose-Einstein condensate confined in an attractive quadratic plus quartic trap are investigated.
Assuming the presence of a large number of vortices we apply the diffused vorticity approach to the system. We then use the
sum rule technique for the calculation of collective frequencies, comparing the results with the numerical solution of the
linearized hydrodynamic equations. Numerical solutions also show the existence of low-frequency multipole modes which are
interpreted as vortex oscillations. 相似文献
976.
Dynamics and Recovery of Genuine Multipartite Einstein–Podolsky–Rosen Steering and Genuine Multipartite Nonlocality for a Dissipative Dirac System via the Unruh Effect 下载免费PDF全文
The dynamics behaviors of genuine multipartite Einstein–Podolsky–Rosen steering (GMS) and genuine multipartite nonlocality (GMN) are investigated herein, and how the lost GMS and GMN under a mixed decoherence system can be recovered is explored. Explicitly, the decoherence system can be modeled by that a tripartite Werner‐type state suffers from the non‐Markovian regimes and one subsystem of the tripartite is under a non‐inertial frame. The conditions for steerable and nonlocal states can be obtained with respect to the tripartite Werner‐type state established initially. GMS and GMN are very fragile and vulnerable under the influence of the collective decoherence. GMS and GMN will vanish with growing intensity of the Unruh effect and the non‐Markovian reservoir. Besides, all achievable GMN's states are steerable, while not every steerable state (GMS's state) can achieve nonlocality. This means that the steering–nonlocality hierarchy is still tenable and GMN's states are a strict subset of the GMS's states in such a scenario. Subsequently, an available methodology to recover the damaged GMS and GMN is proposed. It turns out that the lost GMS and GMN can be effectively restored, and the ability of GMS and GMN to suppress the collective decoherence can be enhanced. 相似文献
977.
基于超流流体力学方程组和标度理论,数值研究了Bardeen-Cooper-Schrieffer (BCS)-Bose-Einstein Condensate (BEC)渡越过程中超流费米气体在线性减小谐振子势下的集体激发.详细研究了包括谐振子势频率线性减小的速度,减小到的幅度以及势阱各向异性参数对集体激发的影响.通过频谱分析和数据拟合,分别研究了各向同性势和各向异性势下在最小振幅激发下所对应的模式,且数值计算得到的频率值在整个BCS-BEC渡越过程中与前期的理论结果符合得很好.该工作可以为后面超流费米气体集体激发的实验提供有益的理论参考 相似文献
978.
In the current research paper, a conservative system comprising of a mass grounded by linear and nonlinear springs in series connection is studied. The equation of motion for the aforementioned system has been derived as a nonlinear ordinary differential equation with inertia and static–type cubic nonlinearities. The global residue harmonic balance method is applied to obtain an approximate analytical frequency and periodic solution of the problem. Using the obtained analytical expressions, the influences of the hardening and softening nonlinear spring on the non–dimensional frequency are investigated. The results show that developing the system nonlinearity leads the displacement of the mass and the deflection of linear spring to approach each other. Moreover, comparison of the results obtained using the proposed procedure with those achieved by other methods such as numerical method, variational iteration method and harmonic balance approach demonstrates the accuracy and advantages of the current approach. 相似文献
979.
A quantum secure direct communication protocol over a collective rotating channel is proposed. The protocol encodes logical bits in noiseless subspaces, and so it can function over a quantum channel subjected to an arbitrary degree of collective rotating noise. Although entangled states are used, both the sender and receiver are only required to perform single-particle product measurement or Pauli operations. The protocol is feasible with present-day technique. 相似文献
980.