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61.
62.
Ohne Zusammenfassung  相似文献   
63.
The way to determine the effective temperature of the excitonic system from the study of the edge luminescence high energy region is motivated. Experimental data on the exciton heating in ZnSe single crystals under laser excitation are presented. The effective temperature of excitons Tx has reached 158 K at the lattice temperature TL = 77 and the peak excitation intensity 2.7 MW cm?2 (hv0 = 3.50), while the excess temperature of the excitons (Tx ? TL) increases as a square root of the pump intensity. Exciton-hot-electron, exciton-hot-photon, exciton-exciton interactions and excitonic Auger process are considered as possible causes of the exciton system heating.  相似文献   
64.
The temperature dependence of the 17O NQR spectra of the O-H---O bonded oxygens in PbHPO4 have been studied using a proton-17O double resonance technique. The results show that the protons move between two off-centre sites above Tc and freeze into one of the possible equilibrium sites below Tc.  相似文献   
65.
In this paper we study some mappings of skew ruled surfaces in simply isotropic space which preserve the generators. We study isometries, conformal mappings and mappings which preserve the area. Furthermore, we study mappings of surfaces in I 3 1 which preserve the asymptotic lines.Received December 18, 2001; in revised form July 12, 2002 Published online April 4, 2003  相似文献   
66.
Proton transfer in hydrogen‐bonded organic co‐crystals of chloranilic acid with some organic bases was investigated by nuclear quadrupole resonance (NQR) spectroscopy. The 35Cl NQR frequencies of chloranilic acid molecule as well as 14N NQR frequencies of the organic base molecule were measured with the conventional pulse methods as well as double‐resonance methods, respectively. The extent of proton transfer in the O···H···N hydrogen bond was estimated from Townes–Dailey analysis of the 14N NQR parameters. The 35Cl NQR frequency and molecular geometry of chloranilic acid are correlated to the extent of proton transfer in the protonation process of the organic base molecule. It is shown that the hydrogen bond affects the π‐electron system of chloranilic acid. Geometry dependence of the O···H···N hydrogen bond, i.e. the H? N valence bond order versus the hydrogen‐bond geometry correlation is also discussed. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   
67.
A simple method has been developed for the determination of arsenic and antimony in environmental samples by solid sampling electrothermal atomic absorption spectrometry, which was validated using certified reference materials of soils (S-VM — Soil Eutric Cambisol; S-MS — Soil Orthic Luvisols; S-SP — Soil Rendzina), sewage sludge (WT-L; WT-M) and sediments (NIES2; GBW07906). The analytical procedure combines solid sampling with utilization of a matrix modifier admixture containing 5 µg of W and 5 µg of Mg. The tungsten in the admixture serves to stabilize the solid matrix during atomisation, which results in dramatically reduced non-specific absorption compared with the conventional palladium modifier. Magnesium was efficient in reducing the accumulation of the matrix residue on the platform. An alternative resonance line of 197.2 nm for arsenic and 206.8 nm for Sb was used in order to eliminate the spectral interferences caused by aluminum compounds, and silicon and iron compounds, respectively. Under optimized experimental conditions, the effective in situ analyte/matrix separation was achieved so that the use of aqueous standards for calibration became possible. With the modifier, a 3 SD detection limit of 0.5 µg g1 As and 0.1 µg g1 Sb and 10 SD quantification limit of 1.7 µg g1As and 0.3 µg g1 Sb and a characteristic mass of 65 pg As and 53 pg Sb were obtained. For all the matrices under scrutiny, a good agreement with certified values was achieved with RSD values less than 10%.  相似文献   
68.
The problem of the transient time in nucleation is studied. The size-dependent transient time at a constant temperature is defined and the approximate analytical solution is found and compared with the exact numerical solution for the model Li2O.2 SiO2 melt. It is shown that the analytical solution for the size-dependent transient time is in agreement with the numerical result.  相似文献   
69.
A crystal distribution function is established during the crystallization process of simple glass-forming melts on the basis of the numerical computation of the kinetic equation in a non-stationary regime for constant and non-constant temperature. Nucleation rate and time-temperature-transformation curves are determined from the calculations of the crystal distribution function at various constant temperatures for various parameters of the system (the dependence on the difference of the chemical potentials, the dependence on the surface energy etc.).  相似文献   
70.
A new two-dimensional depolarization pulse sequence is applied on the static powder sample of ferrocene. The transient oscillations during the first stage of the depolarization process are used for the modulation of magnetization during the evolution period giving the dipolar coupling/chemical shift resolved spectrum.  相似文献   
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