Far-infrared vibrational properties of high-pressure-high-temperature C60 polymers and the C60 dimer

We report high-resolution far-infrared transmission measurements of the 2 + 2 cycloaddition C-60 dimer and two-dimensional rhombohedral and one-dimensional orthorhombic high-pressure high-temperature C60 polymers. In the spectral region investigated(20-650 cm(-1)), we see no low-energy interball modes, but symmetry breaking of the linked C-60 balls is evident in the complex spectrum of intramolecular modes. Experimental features suggest large splittings or frequency shifts of some IhC60-derived modes that are activated by symmetry reduction, implying that the balls are strongly distorted in these structures. We have calculated the vibrations of all three systems by first-principles quantum molecular dynamics and use them to assign the predominant IhC60 symmetries of observed modes. Pur calculations show unprecedentedly large downshifts of T-1u(2)-derived modes and extremely large splittings of other modes, both of which are consistent with the experimental spectra. For the rhombohedral and orthorhombic polymers, the T-1u(2)-derived mode that is polarized along the bonding direction is calculated to downshift below any T-1u(1)-derived modes. We also identify a previously unassigned feature near 610 cm(-1) in all three systems as a widely split or shifted mode derived from various silent IhC60 vibrations, confirming a strong perturbation model for these linked fullerene structures

Optimization of electron-beam sustained discharge laser electrodes system

AbstractOne of the basic problems at creation of powerful electron-beam sustained discharge lasers is achievement of the greatest possible intensity of an electric field in the charge volume limited to the aperture of the resonator and uniformity of power pumping on this volume. In our opinion known types of electrodes, for example,, etc. are not optimum, and the recommendations hallmarking a ratio of electrodes width to interelectrodes distance as 4:1, are a little bit overestimated.It is shown, what even at high uniformity of an electric field in the interelectrodes volume covered with the optical resonator, heterogeneity of pumping power density in cross section of the charge can reach 100%

Modeling of Wire Electrochemical Micromachining

AbstractWire electrochemical micromachining (WECMM) is a promising method for the fabrication of various metal parts. In recent years, WECMM has attracted increasing interest, especially for treatment of complex-shaped microworkpieces. By now, the regularities of electrochemical shaping for the complex-shaped workpieces have not been adequately investigated, because the majority of the works, which are devoted to WECMM, are experimental.In this work WECMM is studied theoretically. The Laplace equation for the electric potential and the equation of workpiece surface evolution are used as the mathematical model of the process. A scheme of computer simulation involves the numerical solution of the Laplace equation by the boundary element method; the determination of a new position of workpiece surface with regard for possible topological changes; and the motion of wire tool-electrode along a prescribed trajectory. Various schemes of shaping for the tool-electrodes with various cross-section shapes and various types of motions are analyzed. As a result of simulation, the dependences of the front and side interelectrode gaps on the machining parameters are obtained. They can be used for determining the path of wire tool-electrode in order to obtain the prescribed shape and sizes of workpiece surface

Electron motion in a Holstein molecular chain in an electric field

A charge motion in an electric field in a Holstein molecular chain is modeled in the absence of dissipation. It is shown that in a weak electric field a Holstein polaron moves uniformly experiencing small oscillations of its shape. These oscillations are associated with the chain’s discreteness and caused by the presence of Peierls-Nabarro potential there. The critical value of the electric field intensity at which the moving polaron starts oscillating at Bloch frequency is found. It is shown that the polaron can demonstrate Bloch oscillations retaining its shape. It is also shown that a breathing mode of Bloch oscillations can arise. In all cases the polaron motion along the chain is infinite. Copyright EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg 2011