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41.
J. Herion M. Tapiero J. P. Zielinger N. Benjelloun-Saki W. Beyer 《Fresenius' Journal of Analytical Chemistry》1989,333(4-5):531-534
Summary Photo-induced current transient spectroscopy (PICTS) was performed for thin films of undoped hydrogenated amorphous silicon (a-SiH). Existing theoretical models i.e. the standard model of PICTS (the transient currents are limited by thermal emission of carriers from localized to mobile states) and the recombination model due to Rose (the transient currents are limited by recombination) fail to describe the experimental data. It is concluded that the recombination model has to be extended to arbitrary distributions of the density of states in order to be applicable to the present case.
Untersuchung tiefer Zustände in dünnen Schichten von wasserstoffhaltigem amorphem Silicium mit Hilfe der Photostrom-Transienten-Spektroskopie相似文献
42.
Femtosecond pump pulses are strongly attenuated in lithium niobate owing to two-photon absorption; the relevant nonlinear coefficient beta(p) ranges from approximately 3.5 cm/GW for lambda(p) = 388 nm to approximately 0.1 cm/GW for 514 nm. In collinear pump-probe experiments the probe transmission at the double pump wavelength 2lambda(p) = 776 nm is controlled by two different processes: A direct absorption process involving pump and probe photons (beta (r) = 0.9 cm/GW) leads to a pronounced short-duration transmission dip, whereas the probe absorption by pump-excited charge carriers results in a long-duration plateau. Coherent pump-probe interactions are of no importance. Hot-carrier relaxation occurs on the time scale of < or approximately equal to 0.1 ps. 相似文献
43.
Hsieh HT Psaltis D Beyer O Maxein D von Korff Schmising C Buse K Sturman B 《Optics letters》2005,30(17):2233-2235
Spatial gratings are recorded holographically by two femtosecond pump pulses at 388 nm in lithium niobate (LiNbO3) crystals and read out by a Bragg-matched, temporally delayed probe pulse at 776 nm. We claim, to our knowledge, the first holographic pump-probe experiments with subpicosecond temporal resolution for LiNbO3. An instantaneous grating that is due mostly to the Kerr effect as well as a long-lasting grating that results mainly from the absorption caused by photoexcited carriers was observed. The Kerr coefficient of LiNbO3 for our experimental conditions, i.e., pumped and probed at different wavelengths, was approximately 1.0 x 10(-5) cm2/GW. 相似文献
44.
We investigate the properties of qq and
states in hot and dense quark matter in the framework of light-front finite-temperature field theory. Presently we use the Nambu–Jona-Lasinio model of QCD and derive the gap equation at finite temperature and density. We study pionic and scalar diquark dynamics in quark matter and calculate the masses and the Mott dissociation as a function of the temperature T and the chemical potential μ. For the scalar diquark we determine the critical temperature of color superconductivity. 相似文献
45.
Gumberidze A Stöhlker T Banaś D Beckert K Beller P Beyer HF Bosch F Cai X Hagmann S Kozhuharov C Liesen D Nolden F Ma X Mokler PH Orsić-Muthig A Steck M Sierpowski D Tashenov S Warczak A Zou Y 《Physical review letters》2004,92(20):203004
Radiative recombination transitions into the ground state of cooled bare and hydrogenlike uranium ions were measured at the storage ring ESR. By comparing the corresponding x-ray centroid energies, this technique allows for a direct measurement of the electron-electron contribution to the ionization potential in the heaviest He-like ions. For the two-electron contribution to the ionization potential of He-like uranium we obtain a value of 2248+/-9 eV. This represents the most accurate determination of two-electron effects in the domain of high-Z He-like ions, and the accuracy reaches already the size of the specific two-electron radiative QED corrections. 相似文献
46.
47.
Figarella CF Benkadda S Beyer P Garbet X Voitsekhovitch I 《Physical review letters》2003,90(1):015002
Effects of externally imposed and self-generated poloidal flows on turbulent transport in the edge region of a tokamak are investigated using 3D nonlinear global simulations of resistive pressure-gradient-driven turbulence. Transport reduction is found to be due to synergetic changes in the fluctuation amplitude and in the dephasing of the fluctuations. A scaling of the fluctuation level and turbulent diffusivity with E x B flow shear strength is deduced from these simulations. These scalings agree with recent experimental observations on edge biasing as well as with analytical models. 相似文献
48.
Károly Lázár Nicolas Micheaud R. Magdolna Mihályi Gabriella Pál-Borbély Hermann K. Beyer 《Reaction Kinetics and Catalysis Letters》2001,74(2):289-298
Three variants of solid-state ion exchange were studied. Iron exchange was found to proceed in the first case, in theFeCl2+NH4ZSM-5 FeZSM-5 + NH4Cl process, even at low exchange capacity (Si/Al = 25).The second, Fe2O3 (hematite) + HZ direct reaction does not result in any noticeable interaction for eitherZ = Y or ZSM-5. This process can significantly be promoted by introducing CCl4 vapor via forming chlorine-containingmobile species. However, the structure of the Y zeolite largely collapses during this treatment, whereas the crystalline state of ZSM-5is preserved. 相似文献
49.
E. F. Jones P. M. Gore J. H. Hamilton A. V. Ramayya A. P. de Lima R. S. Dodder J. Kormicki J. K. Hwang C. J. Beyer X. Q. Zhang S. J. Zhu G. M. Ter-Akopian Yu. Ts. Oganessian A. V. Daniel J. O. Rasmussen I. Y. Lee J. D. Cole M. W. Drigert W.-C. Ma 《Physics of Atomic Nuclei》2001,64(7):1157-1164
The levels in 162Gd were identified in spontaneous fission studies. Its transition energies are remarkably similar to those in 160Gd. From that work, an analysis of yrast bands in even-even proton to neutron-rich Ba to Pb nuclei led to the discovery of a new phenomenon, shifted identical bands (SIB). SIBs are yrast bands in neighboring nuclei (a, b) with moments of inertia which are identical when shifted by a constant amount κ, so J 1a (1+κ)=J 1b , from 2+ to 8+ and higher to 16+. Out of over 700 comparisons, 55 SIBs were found from stable to the most neutron-rich Ce-W nuclei with $\left| {\bar k} \right|$ between 1.5% and 13%, where the spread in κ is less than ±1%, and only four identical bands ( $\bar k \cong 0$ ). As examples, we found for 158Sm-160Gd, $\bar k = \left( { - 3.2_{ - 0.2}^{ + 0.1} } \right)\%$ (where the ± is the total spread in κ from ?3.1 to ?3.4); 156Nd-160Gd, (?10.6 ?0.2 +0.4 )%; 158Sm-160Sm, (3.4 ?0.3 +0.5 )%. The J 1 values were fitted to a variable moment of inertia model with parameters J 0 and C whose values correlate with the SIB J 1 values. The SIBs are not correlated either with deformation or with the N p N n product of the IBA model. 相似文献
50.
F. Liu K.J. Daun V. Beyer G.J. Smallwood D.A. Greenhalgh 《Applied physics. B, Lasers and optics》2007,87(1):179-191
Laser-induced incandescence (LII) of nanoparticles at low pressures has received some attention in recent years as a particle
sizing technique or a technique for inferring the mean value of the absorption function of the particle material. In this
paper, we are concerned with some fundamental issues in the theory of LII with particular attention paid to those encountered
at very low pressures. The commonly adopted Rayleigh approximation for particle laser energy absorption and subsequent thermal
emission is critically evaluated against the Mie solution in the range of size parameter relevant to LII. The Rayleigh approximation
can cause significant error in particle laser energy absorption rate, especially when shorter wavelengths are used, and potentially
in the particle temperature inferred from the two-color LII. We also demonstrate that claims that low-pressure LII can be
used for particle sizing are flawed, due to the use of an incorrect expression for radiation heat loss rate from the particles
in this regime, and unjustified neglect of particle sublimation heat loss. Using the currently best available carbon sublimation
rate expression and physical parameters, the relative importance of heat conduction, thermal radiation, and sublimation heat
loss from an isolated carbon particle was investigated for different ambient pressures, particle temperatures and particle
diameters. To ensure particle radiation heat loss is dominant over conduction and sublimation the ambient pressure and the
particle temperature should be kept respectively lower than 10-4 atm and below about 2800 K. Under these conditions the effective temperature of a particle ensemble containing non-aggregated
polydisperse primary particles to the power of -4 is proportional to the mean value of the particle absorption function, provided
the particles are in the Rayleigh regime in the near infrared. The effect of aggregation on particle absorption and emission
is briefly discussed.
PACS 44.10.+i; 44.40.+a; 61.46Df 相似文献