Results 1 - 10 of 441
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[en] A high resolution mapping of quantum Hall edge states has been performed by locally creating electrons with small excess energies with a near-field scanning optical microscope in a dilution refrigerator. We have observed fine structures parallel to the edge in photovoltage signals, which appear only at low temperature. The observed fine structures near sample edges have been seen to shift inward with increase in magnetic field in accordance with Chklovskii Shklovskii, and Glazman model
[en] Various focusing monochromators are compared and evaluated for use in an EXAFS spectrometer. For a line focus the Johann and Johansson cases are found to be most suitable. Obtaining a point focus is more difficult, with the best case appearing to be a singly bent mirror used in conjunction with the Johann or Johansson crystals
[en] A systematic study of high energetic alpha particle interaction with microinstability driven turbulence (ITG) is presented. The alpha particles are considered to be passive, thus not modifying the fine structure of the turbulence, and modelled as Maxwellian distributed. Both the turbulent fields and the evolution of the alpha distribution are computed by means of an Eulerian, flux tube code. It is shown how significant transport of high pressure distributions can occur, and how the direction and the intensity of the particle flux is sensitive to the choice of the temperature scale length of the alpha distribution, due to thermodiffusive phenomena. The diffusivity of an ITER-like case is studied, starting from an analytical treatment of the density and temperature profiles, which we show to be significant. New interpretative tools, by means of a single particle following code, are also presented.
[en] Optical frequency metrology plays an important role for the determination of the Rydberg constant and offers an alternative way to determine the fine structure constant α. We have developed a new technique for measuring optical frequencies using femtosecond light pulses culminating in the single laser optical frequency synthesizer. This new technique greatly simplifies the task of measuring optical frequencies
[en] The photodetachment cross section of a charged particle bound in a short range potential is an oscillating function of frequency of incident light, in the presence of a magnetic field. The theory of this effect is described, and calculated cross sections are shown. For photodetachment of electrons from negative atomic ions, this constitutes an additional magnetic field effect beyond the ones associated with fine and hyperfine structure of the ion and atom and with spin of the detached electron
[en] Precise radio frequency spectroscopy of non-penetrating, high angular momentum Rydberg states of helium tests many fundamental aspects of the physics of two-electron atoms. In addition, these studies provide the most precise tests of theories of long-range ''retardation'' or ''Casimir'' forces, which are of more general interest, and which have not traditionally been considered within the context of detailed atomic structure calculations. The high-L, n=10 states of helium have now been studied experimentally with a precision that approaches the fundamental limits set by the their natural linewidths, using fast beam microwave-optical techniques developed for this purpose. Comparison between the most recent experimental results and theoretical predictions confirms at the few percent level the predicted long-range interactions due to two-photon exchange, which contain the ''retardation'' contributions. Significant discrepancies remain, however, which point to the need for continued refinement of the theoretical calculations
[en] We have investigated experimentally excitonic properties in organic-inorganic hybrid multi quantum well crystals, (C4H9NH3)2PbBr4 and (C6H5−C2H4NH3)2PbBr4, by measuring photoluminescence, reflectance, photoluminescence excitation spectra. In these materials, the excitonic binding energies are enhanced not only by quantum confinement effect (QCE) but also by image charge effect (ICE), since the dielectric constant of the barrier layers is much smaller than that of the well layers. By comparing the 1s-exciton and 2s-exciton energies, we have investigated the influence of ICE with regard to the difference of the Bohr radius
[en] We examine in this work the expression of the dipolar autocorrelation function for an emitter in the plasma using the path integrals formalism. The results for Lyman alpha lines with fine structure are retrieved in a compact formula. The expression of the dipolar autocorrelation function takes into account the ions dynamics and the fine structure effects. The electron's effect is represented by the impact operator Φe in the final formula.
[en] There are a lot of methods dealing with the problems how to get the local radial intensity from a measured lateral intensity of the spectral line. All of them need some a priori information and often a preliminary filtering of the signal. Thus, it is always a question about loosing the useful information of the signal. One of the methods for determination radial intensity is a Tikhonov regularization method. This method requires minimum a priori information such as: the intensity is a monotone positive function. To check applicability limitations of the method, some model functions have been introduced. Special attention was devoted to the model function with the fine structure
[en] Proton radioactivity from deformed drip-line nuclei is discussed. It is shown how it is possible to describe all experimental data currently available for decay from ground and isomeric states, and fine structure within a consistent theoretical approach