Plasma oscillations in fullerene molecules within the random phase approximation

A method is presented for calculating the density of plasma excitation modes in fullerene molecules, which makes it possible to describe more accurately the specific features of the spectra as compared to the models proposed previously. The method is based on the inclusion of the total contribution of π and σ electrons to the spectra of collective oscillations in the molecules. This allows one to consider fullerene molecules with an arbitrary symmetry and arbitrary substituents. A comparative analysis of the experimental curves obtained for resonance electron capture and the results of numerical simulations for C₆₀, C₇₀, and C₇₆ molecules has demonstrated that not only the main maxima but also the ranges of the formation of negative ions coincide.     

Coherent electron density distribution oscillations in electron capture by fast protons in helium

Assuming the validity of a recent model of Lyman-α beat behaviour from fast H atoms under conditions of reversal of an applied electric field, we find strong electric dipole density distribution oscillations in electron capture to n=2 levels of hydrogen by fast protons (≈ 2 au) in helium. Possibilities for testing relative orbital phase calculations in charge-transfer theory, and for making comparisons between beam-surface and single ion-atom collision models of projectile passage through solids exist.     

Z oscillations in ion-induced fullerene fragmentation

Multiply charged ion-induced fragmentation and ionization of C60 is governed by electronic and nuclear stopping of the projectile as well as charge exchange. We have studied the collision dynamics as a function of the projectile atomic number Z ( 2相似文献   

Possible explanation of oscillations of the electron capture rate in decays of one-electron ions

On the basis of the idea of mixing (interaction) between the electron capture and the positron emission channels in the β ⁺ decay in the cases when both channels are energetically allowed, we attempt to explain oscillations of the K-capture rates that were possibly seen in recent experiments.     

Plasma oscillations in two-dimensional electron systems with a superstructure under Stark quantization conditions

The effect of quantizing electric field on plasma oscillations of two-dimensional electron gas in a system with a periodic potential has been theoretically investigated. The coupled-plasmon spectrum ω(q) is calculated for high temperatures (Δ ? T, where Δ is the conduction miniband width and T is temperature in energy units). The calculations are based on the quantum theory of plasma oscillations in the random-phase approximation, with allowance for the umklapp processes.     

Ultrafast dissociation and electron excitation in polyatomic organic molecules upon multiple IR photon capture

We suggest a model that allows analysis of the photoprocesses in polyatomic organic molecules upon multiple IR photon capture. The dissociation and electron excitation of these molecules is shown to depend resonantly on the photon energy and intensity. The (CH₂)_n substructures of these molecules serve for IR photons as antennas that accumulate energy to values at which dissociation or electron excitation can be triggered. The model is applied to diphenylalkan molecules as an example.     

Low energy electron oscillations during epitaxial growth of thin films

We have measured the specularly reflected intensity of low energy (12 eV) electrons as a function of the deposition time during the growth of Cu-thin films on fcc-Co(100) and Co-thin films on Cu(100). The measured curves show pronounced periodical oscillations. The origin of these oscillations is identified as arising from the interference of the electron waves reflected at the vacuum-film and film-substrate boundaries.     

足球烯分子三阶非线性光学性质的研究

报道了有关足球烯分子甲苯溶液中简并四波混频实验.测量出足球烯C_(70)分子和C_(60)分子的三阶超极化率张量y_(1111)分量分别为1.2×10~(-30)esu和4.0×10~(-31)esu.对应于固体样品的三阶非线性光学系数X_(1111)分量分别是2.5×10~(-8)esu和8.5×10~(-9)esu.此结果表明了足球烯分子是现有的非线性光学材料中具有较大三阶非共振电子极化率材料之一.文中还利用自由电子模型解释了非线性光学极化率的起源.     

Plasma oscillations in a two-dimensional semimetal

Collective oscillations of an electron-hole plasma in a two-dimensional semimetal have been investigated. It has been shown that two undamped branches of plasma oscillations exist under certain conditions on the parameters of the structure. Acoustic plasmons are not damped in a finite wavenumber range. When the Fermi velocities of the electrons and holes are equal to each other, this range expands to the range of the applicability of the theory (the momentum of the plasmon is much lower than the Fermi momenta of the particles).     

Giant oscillations of electron temperature during steady-state operation on Tore Supra

During fully noninductively driven discharges in the Tore Supra tokamak, large spontaneous oscillations of the core electron temperature (DeltaTe/Te>50%) have been observed for the first time. They occurred during the standard O regime, which is itself characterized by periodic oscillations of much smaller amplitude. The "giant" oscillations appear to involve distinct mechanisms with respect to the O regime and provide a spectacular example of the complex nonlinear interactions between energy confinement, noninductive current sources, and MHD that may occur in a tokamak plasma during steady-state operation.     

Double internal bremsstrahlung in electron capture

Double internal bremsstrahlung has been observed in the electron capture decay of ³⁷Ar. The energy distribution of the two photons has been investigated, using a dual parameter pulse-height analysis system, at an angle of θ = 90° between two photon propagation vectors. For sum photon energies in the interval of 210–810 keV and at θ = 90° the ratio of the transition probabilities of double to single bremsstrahlung emissions was found to be (4.8±0.4)×10^?5.     

Plasma oscillations and dynamical friction

The forceF of mutual interaction of two species of charged particles in relative motion with velocityU is, forU higher than the mean thermal velocities of particles, a decreasing function ofU. This property ofF(U) can give rise to the excitation of electrostatic oscillations.

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F, copta , U, U, , , U. F(U) .

     

Large amplitude electron plasma oscillations

We consider a cold plasma in order to find new large-amplitude wave solutions in the long-wavelength limit. Accordingly we derive two generic coupled equations which describe the energy exchange between the electrostatic and electromagnetic waves. A new kind of quasi-periodic behavior is found. Our derivations may be considered as a prerequisite to extended studies of stimulated Raman scattering for cases where the wave amplitudes are so large that standard perturbation techniques are not applicable.