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Knyukshto V.N.,B. I. Stepanov Institute of Physics | Volkovich D.I.,B. I. Stepanov Institute of Physics | Gladkov L.L.,Higher State College of Communications | Kuzmitsky V.A.,Institute for Command Engineers | And 4 more authors.
Optics and Spectroscopy (English translation of Optika i Spektroskopiya) | Year: 2012

We have performed complex experimental and theoretical investigations of the spectral-luminescent properties and electronic structure of new phthalocyanine analogs, Mg octaphenylporphyrazine and its derivatives with an annulated thiadiazole or selenadiazole ring instead of two phenyl groups. Fluorescence characteristics have been determined at 293 and 77 K: emission, excitation, and fluorescence polarization spectra; fluorescence quantum yield φF, and lifetime τF. Annulation of a five-membered chalcogen-containing heterocycle leads to splitting of the long-wavelength absorption band Q(0-0) and to the bathochromic shift of its longest wavelength component Qx(0-0), which increase upon passage from S to Se. At the same time, the fluorescence quantum yield φF and lifetime τF decrease, which is related to the intramolecular heavy-atom effect. The geometric structure of the ground state of the Mg porphyrazine molecules has been determined based on the density functional theory (DFT), and excited electronic states have been calculated with modified parametrization of the INDO/S method, INDO/Sm. Semiquantitatively, the calculated level positions of the lowest Q states and spectral shifts of Mg octaphenylporphyrazine and S-derivative agree with experimental data. For the range of the Soret band, calculated transition energies and their intensity distributions substantially depend on the dihedral angle γ between a phenyl ring and porphyrazine macrocycle. We show that, based on calculations at the angle γ = 60°, bands in the observed absorption spectra can be assigned with an accuracy of ~2000 cm-1. © Pleiades Publishing, Ltd., 2012. Source


Klimovich A.S.,University of Bialystok | Solov'Ev V.V.,Higher State College of Communications
Journal of Computer and Systems Sciences International | Year: 2011

The problem of minimization of Moore finite-state machines (FSMs) is considered. This problem often arises in designing digital devices based on programmable logic devices. The proposed approach uses the operation of merging of two states of an FSM and the representation of the FSM as a list of transitions. Conditions guaranteeing the identical operation and deterministic behavior of the transformed FSM obtained by merging two states are given. The cases when wait states can emerge are also discussed. Algorithms for minimizing the number of internal states, transition paths, and the number input variables of Moore FSMs are described. Experimental results have shown that the proposed approach reduces the number of internal states by 6% on the average and sometimes by a factor of 1.86; the number of transitions is reduced by 20% on the average and sometimes by a factor of 2.83. The use of the proposed method in combination with the STAMINA computer program reduces the number of internal states by 16% on the average and sometimes by a factor of 2.17; the number of transitions is reduced by 41% on the average and sometimes by a factor of 7.97. In conclusion, important directions of research concerning the minimization of FSMs are discussed. © 2011 Pleiades Publishing, Ltd. Source


Gladkov L.L.,Higher State College of Communications | Gaponenko S.V.,B. I. Stepanov Institute of Physics | Shabunya-Klyachkovskaya E.V.,B. I. Stepanov Institute of Physics | Shimko A.N.,B. I. Stepanov Institute of Physics | And 2 more authors.
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2014

Vibrational states of the newly synthesized molecule N′-(Adamantan-2- ylidene)thiophene-2-carbohydrazide, a potential antibacterial agent, are examined experimentally for the crystalline phase and analyzed based on quantum chemical modelling of the solitary molecule and of the dimer, and assignment of the observed vibrational frequencies is proposed. Modelling of the title molecule dimer is found to describe better the experimentally observed vibration frequencies for the crystalline phase than calculations performed for a solitary molecule. Contributions from adamantane and thiophene parts within the molecule are identified. Additionally, multiple hydrogen bonds have been revealed both experimentally and computationally, inherent in the crystalline phase contrary to a solitary molecule. The spectroscopic findings correlate with the calculated interatomic distances which were found to change in the dimer versus a single molecule and to correspond better to the X-ray analysis data of the title compound in the crystalline phase. © 2014 Elsevier B.V. All rights reserved. Source


Volkovich D.I.,B. I. Stepanov Institute of Physics | Gladkov L.L.,Higher State College of Communications | Kuzmitsky V.A.,Institute for Command Engineer of the Ministry of Emergency Situations of the Republic of Belarus | Solovyov K.N.,B. I. Stepanov Institute of Physics
Journal of Applied Spectroscopy | Year: 2011

Geometric structures and excited electronic states for free bases of bacteriochlorin (H2BC) and tetraazabacteriochlorin (H2TABC) as well as for their magnesium complexes (MgBC and MgTABC), analogs of bacteriopheophytin a (H2BPhea) and bacteriochlorophyll a (MgBPhea), have been calculated by a DFT method and by an INDO/Sm method (the INDO/S method with parameterization modified by the authors), respectively. The factors responsible for the observed bathochromic shift of the long-wavelength Qx(0-0) band of MgBPhea relative to H2BPhea, δEQx ≅ -300cm-1, have been clarified. Contributions of one- and two-electron interactions to the resulting shift of the Qx(0-0) band have been analyzed in detail for the H2BC/MgBC, H2TABC/MgTABC, and porphine (H2P)/Mg porphine (MgP) pairs. It is shown that the bathochromic shift under consideration for the tetrahydro derivatives is caused by a decrease of the orbital energy gap ε1-ε-1 between the lowest unoccupied and highest occupied molecular orbitals. The variation of δ(ε1-ε-1) is large and amounts to -1660 and -920 cm-1 for the H2BC/MgBC and H2TABC/MgTABC pairs, respectively. The two-electron contributions, both into the energy of electronic configurations and due to the superposition of the configurations, produce a compensating hypsochromic effect such that the shifts δEQx are -260 and -150 cm-1 for the H2BC/MgBC and H2TABC/MgTABC pairs, respectively. It is also shown that the calculated electronic spectra for the considered molecules agree quantitatively with the experimental absorption spectra. © 2011 Springer Science+Business Media, Inc. Source


Gladkova O.L.,Higher State College of Communications | Parkhats M.V.,B. I. Stepanov Institute of Physics | Gorbachova A.N.,B. I. Stepanov Institute of Physics | Terekhov S.N.,B. I. Stepanov Institute of Physics
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2010

Fourier transform infrared spectra of chlorin e6 and its trisodium salt are presented. The geometrical structure and frequencies of normal vibrations of both compounds were calculated using density functional method with the PBE exchange-correlation functional. The frequencies were assigned and IR spectra of the studied molecules were interpreted for the first time. Spectral effects of degradation of chlorin e6 and its trisodium salt upon their storage on the air are analyzed. The possible structures of degraded species are discussed. © 2010 Elsevier B.V. All rights reserved. Source

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