Quantenchemische Untersuchung der Reaktionsfähigkeit von π-Elektronen-Systemen in angeregtem Singulett- und Triplettzustand

Zusammenfassung Anhand der Methode der Konfigurationenwechselwirkung wurde die Ladungsdichteverteilung in einer Reihe von aromatischen Aminen und N-haltigen Heteroaromaten im angeregten Singulett- und Triplettzustand untersucht. Durch die Untersuchungen wurde die Formulierung der folgenden Regel ermöglicht: im angeregten Singulett- und Triplettzustand ist die Basizität bei den Aminen wesentlich vermindert; die N-haltigen Heteroaromaten weisen im angeregten Singulettzustand eine erhöhte Basizität auf, und im Triplettzustand tritt eine Verminderung der Basizität ein.

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The electron density distribution in excited singlet and triplet states of a number of aromatic amines and heterocyclic compounds containing nitrogen atoms is studied using the CI-method. The investigation allows the formulation of the following rule: in excited singlet and triplet states the amines possess significantly reduced basicity; the nitrogen heterocyclic compounds in excited singlet states increase their basicity, whereas in excited triplet states their basicity is decreased.

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Résumé Au moyen de la méthode d'interaction de configuration, on a étudié la répartition de la densité électronique dans un certain nombre d'aminés aromatiques et de composés hétérocycliques azotés dans l'état excité singulet et triplet.Les études effectuées ont permis d'établir la règle suivante: à l'état excité singulet ou triplet la basicité des aminés est sensiblement réduite; la basicité des composés N-hétérocycliques augmente dans l'état excité singulet et diminue dans le triplet.

     

Micellization and interfacial properties of alkyloxyethylene sulfate surfactants in the presence of multivalent counterions

Alkyloxyethylene sulfates are a special class of surfactants that are unusually stable in the presence of multivalent counterions and are not as prone to precipitation as anionic surfactants without intermediate ethoxy groups in the molecule. However, formation of micelles, their structure, and the properties of monolayers of these surfactants exhibit very interesting and sometimes unexpected properties depending on the nature of the ions dissolved in the solution. This paper presents a brief overview of our recent efforts to reveal the nature of these properties, including some new results. We show that the strong binding of multivalent (and particularly trivalent counterions) triggers a sphere-to-cylinder shape transition of the micelles and facilitates their further growth, even at very low ionic strength. The properties of surfactant monolayers are coupled to those of the micelles in the bulk and are governed also by multivalent counterion binding. The effect of multivalent counterions on the aggregation and structure formation in anionic surfactant solutions has both fundamental and practical importance.     

Searching for Neutrino and Ultra-High-Energy Gamma-Ray Counterparts of the GCN Alerts

Physics of Atomic Nuclei - The Baksan Neutrino Observatory setups are currently performing search for neutrino and ultra-high-energy gamma-ray counterparts of the events on the Gamma-ray...     

Strongly enhanced quadrupole deformation in a class of N≈Z nuclei driven by large-scale clustering?

The formation of large size clusters,and/or their relative motion as a possible excitation mode,are sugge sted to be closely related to the origin of deformation in specific cases,namely the case of two doubly-magic clusters or two clusters with nearby characterization.New lifetime data in N=Z ~(76)Sr and ~(80)Zr leading to large B(E2) values are reproduced consistently and well within this approach,along with data for a few neighboring N≈Z nuclei.These results are compared to previous studies of ~(32)S and ~(20)Ne and all of them support the ideas of the large-scale cluster approach.     

Measurements of cavitation bubble dynamics based on a beam-deflection probe

We present an optodynamic measurement of a laser-induced cavitation bubble and its oscillations based on a scanning technique using a laser beam-deflection probe. The deflection of the beam was detected with a fast quadrant photodiode which was built into the optical probe. The applied experimental setup enabled us to carry out one- or two-dimensional scanning of the cavitation bubble, automatic control of the experiment, data acquisition and data processing. Shadow photography was used as a comparative method during the experiments.     

Investigating the influence of a Forbush decrease on the detected flux of high-energy muons

The effect of Forbush decreases was studied for a flux of high-energy muons with a threshold of 220 GeV detected by the Baksan Underground Scintillation Telescope (BUST) of the Institute for Nuclear Research, Russian Academy of Sciences.     

A possibility for studying the fluctuations of the multiplicity in muon bundles

Fluctuations of the multiplicity in muon bundles is another characteristic of these bundles and can provide additional information both about the spectrum and composition of primary cosmic rays and about the model of their interaction. In this paper, the possibility of studying these fluctuations using the data of the Baksan underground scintillation telescope is considered.     

Experimental search for gamma-ray bursts from evaporating primordial black holes

The energy spectra and temporal characteristics of high-energy gamma-ray bursts from evaporating primordial black holes have been calculated using various evaporation models. The currently existing theoretical uncertainties in the shape of the evaporated photon spectrum are discussed. The data from the Andyrchy and Carpet-2 arrays of the Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences) obtained in the mode of detection of a single cosmic-ray component are used to search for cosmic gamma-ray bursts with a primary photon energy of about 8 GeV. New upper limits have been obtained for the number density of evaporating black holes in a local region of space with a characteristic size of ～10^?3 pc for various evaporation models.     

Hadrons with energies higher than 50 MeV in EASes with <Emphasis Type="Italic">N</Emphasis><Subscript><Emphasis Type="Italic">e</Emphasis></Subscript> = 10<Superscript>5</Superscript>–10<Superscript>7</Superscript>

Characteristics of the hadronic component of EASes with hadron energies E _h > 50 MeV were measured on the CARPET-2 complex shower array at the Baksan Neutrino Observatory of the Institute for Nuclear Research, Russian Academy of Sciences. Hadrons were registered using a 6-NM-64 neutron monitor; the data collection system of this array enables us to register the time intervals between pulses of neutron monitor counters with an error of up to 1 μs. For EASes with N _e = 10⁵–10⁷ whose axes are located in CARPET, we obtain the dependence of the mean neutron multiplicity in the neutron monitor on the total number of charged particles in the EAS.