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251.
G. Giardina G. Fazio A. Lamberto A. I. Muminov A. K. Nasirov U. T. Yakhshiev R. Palamara R. Ruggeri 《Acta Physica Hungarica A》2004,19(1-2):101-108
We study the effect of the entrance channel and the shell structure of reacting massive nuclei on the fusion mechanism and the formation of evaporation residues of heavy and superheavy nuclei. In the framework of the combined dinuclear system concept and advanced statistical model, we analyze the reactions 32S+182W, 48Ti+166Er and 60Ni+154Sm leading to 214Th*, and the reactions 48Ca+248Cm and the 48Ca+249Cf leading to the 296116 and 297118 compound nuclei, respectively. 相似文献
252.
Forces along Equidistant Particle Paths 总被引:1,自引:1,他引:0
Two particles on the sphere leave the equator moving due south and travel at a constant and equal speed along a geodesic colliding
at the south pole. An observer who is unaware of the curvature of the space will conclude that there is an attractive force
acting between the particles. On the other hand, if particles travel at the same speed (initially parallel) along geodesics
in the hyperbolic plane, then the particle paths diverge. Imagine two particles in the hyperbolic plane that are bound together
at a constant distance with their center of mass traveling along a geodesic path at a constant velocity, then the force due
to the curvature of the space acts to break the bond and increases as a quadratic function of the velocity. We consider this
problem for the sphere and the hyperbolic plane and we give the exact formula for the apparent force between the particles.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
253.
J. Wang G. A. Khodaparast J. Kono T. Slupinski A. Oiwa H. Munekata 《Physica E: Low-dimensional Systems and Nanostructures》2004,20(3-4):412
We have used two-color time-resolved magneto-optical Kerr effect spectroscopy to manipulate and detect dynamic processes of spin/magnetic order in a ferromagnetic semiconductor InMnAs. We observed ultrafast photo-induced “softening” (i.e., transient decrease of coercivity) due to spin-polarized transient carriers. This transient softening persists only during the carrier lifetime (2 ps) and returns to its original value as soon as the carriers recombine to disappear. Our data clearly demonstrates that magnetic properties, e.g., coercivity, can be strongly and reversibly modified in an ultrafast manner. We attribute the origin of this unusual phenomenon to carrier-mediated ferromagnetic exchange interactions between Mn ions. We discuss the dependence of data on the pump polarization, pump intensity, and sample temperature. Our observation opens up new possibilities for ultrafast optical manipulation of ferromagnetic order as well as providing a new avenue for studying the dynamics of long-range collective order in strongly correlated many-body systems. 相似文献
254.
G. Borges 《Acta Physica Hungarica A》2004,21(2-4):341-347
We present preliminary results on J/? production in Pb-Pb collisions at 158 GeV/nucleon, obtained in the analysis of the most recent data sample collected by NA50 experiment in year 2000. The results are compared with an updated absorption curve deduced from new high statistics protonnucleus data. The measurements reported here confirm the anomalous J/? suppression already observed by NA50 from previously collected data samples. 相似文献
255.
A. G. Milekhin A. I. Nikiforov M. Yu. Ladanov O. P. Pchelyakov S. Schulze D. R. T. Zahn 《Physics of the Solid State》2004,46(1):92-96
This paper reports on the results of resonant Raman scattering investigations of the fundamental vibrations in Ge/Si structures with strained and relaxed germanium quantum dots. Self-assembled strained Ge/Si quantum dots are grown by molecular-beam epitaxy on Si(001) substrates. An ultrathin SiO2 layer is grown prior to the deposition of a germanium layer with the aim of forming relaxed germanium quantum dots. The use of resonant Raman scattering (selective with respect to quantum dot size) made it possible to assign unambiguously the line observed in the vicinity of 300 cm?1 to optical phonons confined in relaxed germanium quantum dots. The influence of confinement effects and mechanical stresses on the vibrational spectra of the structures with germanium quantum dots is analyzed. 相似文献
256.
A. V. Turik A. I. Chernobabov G. S. Radchenko S. A. Turik 《Physics of the Solid State》2004,46(12):2213-2216
Effective complex piezoelectric and dielectric constants of disordered heterogeneous systems, such as statistical mixtures consisting of spheroidal particles of the same orientation but with random distribution in space, are studied. It is found for the first time that, in such systems, there exists giant piezoelectric enhancement accompanied by giant relaxation of piezoelectric coefficients and permittivity. The piezoelectric and dielectric spectra differ considerably from the Debye spectra and have a Cole-Cole character. The dependence of the effects considered on the aspect ratios of the spheroids is investigated. The physical mechanisms responsible for the anomalous behavior of the piezoelectric coefficients and permittivity are considered. 相似文献
257.
G. Busiello R. V. Saburova V. G. Sushkova G. P. Chugunova 《Physics of the Solid State》2004,46(2):316-325
The ageing effect is studied analytically in a disordered quantum system interacting with its surroundings and subjected to an external ac magnetic field. Energy dissipation is due to the interaction of the system with a set of independent harmonic oscillators, imitating a quantum thermal bath. Dynamic equations for the autocorrelation function and linear-response function are derived using the method of closed-path integrals. The effect of an external field is studied on the correlation function and response in the spin-glass and paramagnetic phases. Both functions are found to depend on the spin interaction strength. 相似文献
258.
Spatial parameters of the X-ray radiation produced by a high-voltage nanosecond discharge evolving in air under atmospheric
pressure in the rod (cathode)-plane electrode system with a 10-cm electrode spacing are studied experimentally. A ∼170-ns
voltage pulse with an amplitude of ∼200 kV and 10-ns rise time is applied to the cathode. The photoelectronic method is used
to study, under the same conditions, the integrated (over the gap) characteristics of the radiation, in particular, the duration
of its generation. It is found that, when the size of the X-ray source is not smaller than that of the discharge region of
diffusive luminescence, radiation from the cathode region of the gap is primarily observed (i.e., from the region where the
electric field distribution is sharply inhomogeneous). The X-ray generation is usually observed after the bridging of the
discharge gap, the X-ray pulse having a rise time of ∼3 ns, a duration of ∼10 ns, and an effective radiation energy of ∼6
keV. 相似文献
259.
Stimulated Raman scattering (SRS) in a long-distance fiber-optic communication line with wavelength-division multiplexing (WDM) is studied theoretically at a high power of the signal transmitted. A new criterion for determining the SRS threshold is used to calculate the critical input power versus the number of optical channels and frequency separation between them. The theoretical model is verified experimentally. SRS interaction between two channels in a communication line with an SRS amplifier for which the optical waveguide of the line serves as a nonlinear medium is measured. 相似文献
260.
G. A. Shulman 《Russian Physics Journal》2004,47(2):115-123
In addition to the solution of the quantum mechanical problem on the motion of a free electron in a magnetic field, given by L. D. Landau in his pioneering work, this quantum mechanical problem is solved in view of the fact that the sum of the components of the free kinetic energy of an electron along two axes is a periodic quantity varying identically within the boundaries of every Landau energy level. This periodicity is a consequence of the quantized motion of an electron in a plane normal to the direction of the external magnetic field. 相似文献