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1.
2.
P. K. Kashkarov B. V. Kamenev M. G. Lisachenko O. A. Shalygina V. Yu. Timoshenk M. Schmidt J. Heitmann M. Zacharias 《Physics of the Solid State》2004,46(1):104-108
The photoluminescence spectra and kinetics of both erbium-doped and undoped multilayer structures of quasi-ordered silicon
nanocrystals in a silicon dioxide matrix were studied. It was shown that the optical excitation energy of silicon nanocrystals
2–3 nm in size can be practically completely transferred to Er3+ ions in the oxide surrounding the nanocrystals, with its subsequent radiation at 1.5 μm. Possible reasons for the high excitation
efficiency of the Er3+ ions are discussed, and the conclusion is drawn that the F?rster mechanism is dominant in the energy transfer processes occurring
in these structures.
__________
Translated from Fizika Tverdogo Tela, Vol. 46, No. 1, 2004, pp. 105–109.
Original Russian Text Copyright ? 2004 by Kashkarov, Kamenev, Lisachenko, Shalygina, Timoshenko, Schmidt, Heitmann, Zacharias. 相似文献
3.
Andreas Wallner Margit Hölbling Judith Baumgartner Christoph Marschner 《Silicon Chemistry》2007,3(3-4):175-185
A number of cyclo-and bicyclosilanes have been prepared and structurally characterized by X-ray crystallography and Raman
spectroscopy. 1,1,4,4- and 1,1,3,3-tetrakis(trimethylsilyl)octamethylcyclohexasilanes were found to exhibit unusual twist- and twisted boat-conformations. The UV absorption properties of all compounds were studied and found to show absorption maxima red shifted
compared to the parent compound dodecamethylcyclohexasilane.
Dedicated to Prof. Mitsuo Kira on the occasion of his reception of the Wacker Silicon Award 2005 and in recongnition of his
numerous outstanding achievements in organosilicon chemistry. 相似文献
4.
H. Zacharias 《Applied Physics A: Materials Science & Processing》1988,47(1):37-54
In this article the application of tunable dye lasers to desorption phenomena is illuminated. These lasers provide radiation continuously tunable from 105 nm in the vacuum ultraviolet to about 10 m in the mid-IR. By employing either laser induced fluorescence (LIF) or resonance enhanced multiphoton ionization (REMPI) spectroscopy almost all diatomic and many polyatomic molecules can be probed with the sensitivity required to detect desorbing molecules under UHV conditions. The spectral resolution of the lasers is sufficiently high that rotational state selectivity is achieved. Recent developments permit in addition the velocity distributions of molecules to be determined with internal quantum state resolution. Therefore very detailed information about the molecular dynamics has been obtained. In most experiments so far reactive recombinations off surfaces have been investigated. In this paper special emphasis will be given to the recombination of hydrogen on copper and palladium surfaces. For these systems very detailed data about the internal state populations at various surface temperatures have been obtained. The rotational cooling previously observed in molecular beam scattering has also been established for desorption. Strong vibrational excitation has been observed, which in the case of desorption from copper may be associated with the recombination dynamics, whereas for desorption of D2 from Pd(100) a molecular precursor state might be responsible. By measuring the velocity distribution in each quantum state, the complete energetics of the desorbing molecules has been determined. Some first experiments on laser induced desorption with state selective detection of the desorbing molecules will also be discussed. Finally, making use of the polarization analysis of the signal, alignment effects in the desorption can be observed, permitting observation of molecular dynamics with a magnifying glass.Heisenberg fellow of the Deutsche Forschungsgemeinschaft 相似文献
5.
A number of novel N-protected β-amino nitriles were prepared as substrates for two nitrile-converting microorganisms, Rhodococcus sp. R312 and Rhodococcus erythropolis NCIMB 11540. The respective biotransformation products, β-amino acids, are known to be pharmacological very potent compounds. 相似文献
6.
The thermal decompositions of-AlF3 · 3H2O, AlF3 · 3.5H2O, AlF3 · 1.5H2O,-AlF3 and hydroxyfluorides of aluminium were investigated. The literature data were complemented with X-ray results. The first stages of decomposition are described. The AlF3 hydrates and hydroxyfluorides were used as model systems in order to interpret the thermal behaviour of -AlF3 in more detail.
Zusammenfassung Die thermische Zersetzung von-AlF3 · 3H2O, AlF3 · 3,5H2O, AlF3 · 1,5H2O,-AlF3 und Hydroxyfluoriden des Aluminiums wurden untersucht und die in der Literatur beschriebenen Ergebnisse durch Röntgenuntersuchungen ergänzt. Die ersten Phasen der Zersetzung werden beschrieben. Die AlF3-Hydrate und Hydroxyfluoride des Aluminiums können als Modellsystem genutzt werden, um das thermische Verhalten von -AlF3 detailliert zu beschreiben.
-AlF3 · 2, AlF3 · 3,52, AlF3 · 1,52,-AlF3 . . . - lF3.相似文献
7.
8.
Rhodococcus equi A4, Rhodococcus erythropolis NCIMB 11540 and Rhodococcus sp. R312 were investigated towards their ability to produce β-amino amides and acids from β-amino nitriles. The microorganisms show comparable trends: five-membered alicyclic 2-amino nitriles were transformed significantly faster than the six-membered compounds and the products of trans-2-amino nitriles (amides and acids) were formed considerably faster than the cis-counterparts (amides). The trans-five membered nitriles gave the amides (1b, 5b) in excellent enantiomeric excess (94-99%), the biotransformation of trans-six membered substrates resulted in the formation of the acid (3c, 7c) in excellent ee (87-99%). The ee's of the cis-compounds were throughout lower. Fifteen new substances were synthesized and characterized in the course of this work. 相似文献
9.
U. Robra H. Zacharias K. H. Welge 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1990,16(3):175-188
The dynamics of the photodissociation of NO2 into NO(X 2ΠΩ″, ν″=0,J″)+O(3 P 0,1,2) is investigated near the thermodynamic threshold. Cooling the internal degrees of freedom by a supersonic beam expansion provides a nearly complete quantum state selection prior to the predissociation. Measurements of the wavelength dependent dissociation yield into specific product quantum states are reported. At certain wavelengths Λ″ doublet resolved rotational population distributions of the fragments are obtained. Up to an excess energy ofE exc=121 cm?1 about 42% of this energy is partitioned into the rotation of the NO molecules, and correspondingly 58% into the translational degree of freedom. The role of electronic and total parity is discussed. 相似文献
10.
Crystalline title compound (1) prepared from aqueous solution of theophylline and 1,4-diaminobutane has been structurally and thermally characterized. Both the two-step TG decomposition curve and elemental analysis of the hexagonal crystals show that it consists of theophylline and 1,4-diaminobutane in 2:1 molar ratio. Actually, presence of one type of both theophyllinate anions and 1,4-diammoniumbutane dication have been indicated by FTIR spectroscopy. The molecular structure of lattice compound (1) has been determined by single crystal X-ray diffraction, where the hydrogen positions have been obtained from differential Fourier maps. It has confirmed that the crystal is really built up from these ionic constituents bound together with an extensive net of hydrogen bonds. The coupled TG-FTIR analysis of the evolved gases has revealed that the diamine is released as a whole molecule in the first decomposition step. Clathrate 1 and the proton migration in it might serve as a structural model of solid aminophylline whose crystal structure is still unknown. 相似文献