Interaction of metals with an organic semiconductor: Ag and In on PTCDA

The interaction of Ag and In with a thin film of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) was studied by near-edge X-ray absorption fine structure (NEXAFS). Upon Ag deposition on a PTCDA film of 20 nm thickness the relative intensities and lineshapes, as well as the angular dependence of the spectra remains unchanged, illustrating the formation of a chemically unreactive Ag/PTCDA interface. On the other hand, the adsorption of 0.3 nm In strongly decreases the intensity of the π^* resonances in C and O K-edge NEXAFS spectra. This is attributed to a strong charge transfer between In and PTCDA, leading to a redistribution of the charge in the molecule. However, the absence of a strong shift or new features and negligible dependence of peak intensities corresponding to π^* resonances on the In thickness indicate that the interaction between In and PTCDA is not accompanied by a covalent bond formation.     

Specific Features of the Quasilocal State Densities in the Presence of Defects in Media with Spatial Dispersion

The density of stationary quasilocal states of the continuous spectrum arising due to the presence of defects in a medium with spatial dispersion is analyzed. The influence of plane and point defects on the specific features of the spectral quasilocal state density is studied. It is demonstrated that the spectral density has a strict maximum caused by the quasilocal energy level arising in the system. For a plane defect, the energy of the quasilocal level is displaced from the resonance energy of total quasi-particle reflection from the defect. The influence of the quasilocal state on the electronic heat capacity in the presence of the point defect is analyzed.     

An efficient two-step synthesis of 3-allylindoles

A two-step synthetic sequence for an efficient synthesis of 3-allylindoles is described.     

Two-stream-like mechanism of zonal-flow generation by Rossby waves in a shallow rotating fluid

It is shown that the small-scale Rossby waves in a shallow rotating fluid placed in a gravitational field can generate large-scale zonal flows by means of a two-stream-like mechanism. This mechanism is revealed under the conditions when the Lighthill instability criterion is not satisfied. The text was submitted by the authors in English.     

Interaction of cationic 5,10,15,20-tetrakis(4-N-methyl pyridyl) porphyrin with mono-and polynucleotides: A study by picosecond fluorescence spectroscopy

The interaction of water-soluble cationic 5,10,15,20-tetrakis(4-N-methyl pyridyl) porphyrin (H₂TMPyP4) with some mono-and polynucleotides is studied by time-resolved and steady-state fluorescence spectroscopy, as well as by steady-state absorption spectroscopy. The fluorescence decay kinetics are analyzed by reconstructing the decay time distributions, which made it possible to describe in more detail than previously the complexes formed due to the interaction. The main effect of binding of H₂TMPyP4 adenosine 5′-monophosphate and to poly(dA-dT)₂ is shown to be an increase in the fluorescence lifetime from 4.6 ns in the solution to 8.3 and 12.3 ns, respectively. This effect is explained by a less polar (in comparison with water) environment of porphyrin in complexes, which leads to a decrease in the quenching action of the intramolecular charge transfer state between the porphyrin macrocycle and methyl pyridyl groups. In the case of complex formation with guanine-containing nucleotides (guanosine 5′-monophosphate and poly(dG-dC)₂), the effect of decrease in the quenching action of the intramolecular charge transfer state caused by a decrease in the medium polarity is superimposed by a stronger effect of decrease in the fluorescence lifetime of porphyrin as a result of intermolecular electron transfer from guanine to excited porphyrin. A high sensitivity of this intermolecular quenching to the mutual arrangement of the electron donor and the electron acceptor makes it possible to reveal four types of complexes between H₂TMPyP4 and guanosine 5′-monophosphate, which differ in the positions of four broad peaks in the porphyrin fluorescence decay time distribution (0.1, 0.7, 2.4, and 6.1 ns). For the complex with poly(dG-dC)₂, a narrow peak at 2.8 ns prevails in the fluorescence decay time distribution, with the contributions from two additional narrow peaks at 1.0 and 6.2 ns being small.     

Secondary electron distributions,ionization cross sections and loss functions for O(I)–O(V)

An analytic atomic independent-particle-model is used to generate wave functions for the bound and ionization continuum states of O(I), O(II), O(III), O(IV), and O(V). These wave functions are used in conjunction with the Born approximation to generate continuum generalized oscillator strengths (GOS). From these GOS, we obtain secondary electron distributions, which we represent by smooth analytic functions. From the secondary electron distributions, we obtain electron impact ionization cross sections, which are compared to experiment. Finally, we compute the loss functions.