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71.
Poór B Michniewicz N Kallay M Buma WJ Kubinyi M Szemik-Hojniak A Deperasiñska I Puszko A Zhang H 《The journal of physical chemistry. A》2006,110(22):7086-7091
We have unraveled the effects of an amino substituent in the ortho position on the excited-state dynamics of 4-nitropyridine N-oxide by studying the picosecond fluorescence kinetics and femtosecond transient absorption of a newly synthesized compound, 2-butylamino-6-methyl-4-nitropyridine N-oxide, and by quantum chemical calculations. Similar to the parent compound, the S(1) state of the target molecule has significant charge-transfer character and shows a large (approximately 8000 cm(-1)) static Stokes shift in acetonitrile. Analysis of the experimental and the theoretical results leads, however, to a new scenario in which this intramolecular charge transfer triggers in polar, aprotic solvents an ultrafast (around 100 fs) intramolecular proton transfer between the amino and the N-O group. The electronically excited N-OH tautomer is subsequently subject to solvent relaxation and decays with a lifetime of approximately 150 ps to the ground state. 相似文献
72.
73.
G Benedek 《J Phys Condens Matter》2012,24(35):350401
The full text of the biography is available in the pdf provided. 相似文献
74.
G. Benedek P. Nieto J. P. Toennies 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,76(2):237-249
The mechanism behind the intensity oscillations accompanying the flow of
solid helium through a micron-sized orifice into vacuum, called the geyser
effect, is investigated by measuring the pressure pulses at various
locations in the entire flow system. The new results reveal that the source
chamber pressure pulses have the same shape as the external detector pulses
monitored in the previous experiments [G. Benedek et al., Phys. Rev. Lett.
95, 095301 (2005)]. New experiments in which the external gas
reservoir is isolated from the pressure regulator provide direct information
on the mechanism of the collapse leading to the geyser pulses. Thus each
geyser pulse is triggered by the breakdown of a plug located upstream of the
source chamber. The flow of liquid through the orifice determines the shape
of the subsequent geyser pulse. 相似文献
75.
V. Hizhnyakov I. Tehver V. Boltrushko G. Benedek 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,75(2):187-195
A multimode theory of the Raman scattering in resonance with an electronic transition causing a strong weakening of atomic
bonds is proposed. Simple analytical relations between the Fourier transforms of the first- and second-order Raman amplitudes
and the absorption are derived. It is predicted that the Raman scattering on low-frequency vibrations will be strongly enhanced.
Besides the second-order Raman scattering is also enhanced as compared to the first-order scattering. The Raman excitation
profiles show a structure caused by the Airy oscillations. The shapes of the profiles of all vibrations contributing to the
weakening bond are the same as a consequence of the strong mode mixing under the virtual vibronic transition. 相似文献
76.
Summary The LCAO tight-binding method for computing electronic states in insulators and semiconductors has been recently recovered,
in the Green's function formalism, for treating localized perturbations in ideal lattices. After a brief review of this method
applied to surfaces, we face out the problem of a symmetry transformation turning an infinitely thick slab into a semi-infinite
crystal. In this way conceptual and computational simplifications are achieved. We derive a formal expression for the charge
density excess produced by a localized perturbation on the surface layer. This quantity is useful for the problem of inelastic
scattering of atoms by surface phonons.
Gruppo Nazionale di Struttura della Materia del CNR. 相似文献
Riassunto Il metodo LCAO di legame forte, in uso per calcolare gli stati elettronici d'isolanti e semiconduttori, è stato recentemente rivisitato, nel formalismo della funzione di Green, per studiare perturbazioni localizzate in cristalli ideali. Dopo una breve rassegna di questo metodo applicato alle superfici, si affronta il problema di una transformazione di simmetria, che porta da una lastra infinitamente spesso ad un cristallo semiinfinito. Cosí si ottengono delle semplificazioni sia concettuali che di calcolo. Infine si sviluppa un'espressione formale per il cambiamento nella densità di carica prodotta da una perturbazione localizzata che si trovi sullo strato superficiale. Questa quantità è di rilevanza nel problema dello scattering anelastico di atomi da parte di superfici libere.
Резюме Недавно был развит метод ЛСАО сильной связи для вычисления электронных состояний в изоляторах и полупроводниках в формализме триновских функций, для рассмотрения локализованных возбуждений в идеальных решетках. Проводится краткий облему симметричното преобразования бесконечно толстой пластины в полубесконечный кристалл. Зтот подход позволяет получитв схематические и вычислителвные упрощения. Мы выводим формалвное выражение для приращения плотновти заряда, образованното локлизованным возмущнием на поверхности. Зто выражение полезно для решения проблемы неупругого рассеяния атомов на поверхностных фононах.
Gruppo Nazionale di Struttura della Materia del CNR. 相似文献
77.
A small set of easily available epi-cinchona based thiourea organocatalysts have been synthesized and tested in enantioselective Michael addition of nitroalkanes to chalcones. These bifunctional catalyst systems promoted the conjugate additions with high enantioselectivities and chemical yields. The extension of this methodology was further explored to encompass alpha,beta-unsaturated N-acylpyrroles, as a chalcone mimic. Functionally, the N-acylpyrrole moiety in the adduct acts as an ester surrogate; therefore, it can easily be transformed to various valuable and biologically relevant compounds. This approach allowed the concise stereoselective synthesis of (R)-rolipram. 相似文献
78.
79.
Vibrational properties of C20-based solids 总被引:6,自引:0,他引:6
Spagnolatti I. Mussi A. Bernasconi M. Benedek G. 《The European Physical Journal B - Condensed Matter and Complex Systems》2004,38(2):143-145
The European Physical Journal B - The phonon dispersion relations and IR spectrum of a C20-based solid recently identified experimentally [Iqbal et&;nbsp;al. , Eur. Phys. J. B 31, 509 (2003)]... 相似文献
80.
Properties for distances based on neighbourhood sequences on the face-centred cubic (fcc) and the body-centred cubic (bcc) grids are presented. Formulas to both compute the distances and assure that the distances satisfy the conditions for being metrics are presented and proved to be correct. The formulas are used to calculate the neighbourhood sequences that generates distances with lowest deviation from the Euclidean distance. 相似文献