A. N. Solov’ev

Improvement of the parametric method of the theory of vibronic spectra of polyatomic molecules: Absorption spectra and the structure of butadiene, hexatriene, and octatetraene in the excited state

The structure of the excited states and absorption spectra of butadiene, hexatriene, and octatetraene are calculated by the parametric method of the theory of vibronic spectra using models of the first-and second-order approximations. It is shown that these molecular models adequately reflect the molecular structure and allow one to predict quantitatively the shape and fine vibrational structure of the absorption spectra. When passing to the second-order approximation, only two additional (angular) parameters are used. These parameters are transferable in the series of polyenes. Compared to the first-order approximation model, the second-order approximation model more accurately takes into account the angular deformations of polyenes upon their excitation and describes the intensity distribution in the vibrational spectrum, including weak lines. In addition, the calculations also quantitatively predict spectral variations in the molecular series. The parametric method is more efficient for modeling polyatomic molecules in the excited states and their vibrational spectra compared to other semiempirical and ab initio methods.

Modeling vibronic spectra and excited states of polyenes with a parametric method

The structural-dynamic models of excited states and vibronic structure of absorption spectra of linear polyenes (R-(CH=CH)n-R, R=H, CH3, n=4, 5, 7) are calculated using the parametric method of the theory of vibronic spectra of such molecules. Good agreement is obtained between the calculated and experimental spectra. It is shown that the system of parameters of the method for the polyenes has a high degree of transferability in the series of related polyenes. The constructed models adequately reflect the real structure of the molecules in excited states and allow one to predict quantitatively the fine vibrational structure of the spectra, including relatively weak effects related to the methyl substitution. The dynamic of structural changes of the molecules upon their excitation is studied in the series of polyenes.

Identification of crack-like defects in elastic structural elements on the basis of evolution algorithms

A method for the identification of defects in elastic structural elements (SEs) on the basis of artificial neural network (ANN) tools was proposed. The problems of constructing a simulation model of an object, the optimal arrangement of transducers with the use of a genetic algorithm, and the subsequent identification of a defect were solved. The application of different learning architectures and algorithms to feed-forward neural networks (FFNs) was studied and the influence of errors on the estimation accuracy of the parameters of a defect was analyzed.

Calculation and analysis of the excited states and fine structure of vibronic spectra of anthracene, anthracene- d 10 , and tetracene

Structural dynamic models of the excited states of some molecules of the acene series (anthracene, anthracene-d10, and tetracene) have been developed and the vibronic structure of the fluorescence and absorption spectra of these molecules has been calculated by the parametric method of the theory of vibronic spectra. Good agreement is obtained between the calculated and experimental spectra. It is shown that the system of parameters determined for these acenes in the second-order approximation of the method is highly transferable in the acene series. The models proposed adequately describe the real structure of the excited molecules and make it possible to predict quantitatively the fine vibrational structure of the spectra, including relatively weak effects (weak bands, the spectral variations in the series of these molecules, and the variations upon deuterium substitution). The specific features of the structural variations in the investigated acene molecules upon their excitation and the dynamics of these variations in the series of these molecules are studied.

Modeling of the vibrational structure of the vibronic spectra of diphenylpolyenes by the parametric method

The structures of the electronic-vibrational spectra and of the excited states of a number of diphenylpolyene molecules are determined within the framework of the second approximation of the parametric method. The system of parameters of the structural fragments of molecules is improved and good agreement with spectral experiment is obtained. It is shown that there is a high degree of transferability of the polyene and acene parameters of the method and that the models obtained are adequate to the real structure of molecules. It is also shown that the method proposed makes it possible to perform predictive qualitative and quantitative calculations of the spectra of these molecules, as well as of the spectral characteristics necessary for modeling photochemical molecular transformations. In the series of diphenylpolyene molecules, an interpretation of the vibrational structure of the spectra is proposed and the specific features of variation of the geometry upon excitation of molecules are considered.

Modeling of the vibrational structure of the vibronic spectrum and an excited state of the dinaphthylethylene molecule

The vibrational structure of the fluorescence spectrum and the structure of a dinaphthylethylene molecule in an excited state are calculated in the first and second approximations of the parametric method employed in the theory of vibronic spectra. The calculated spectra are in quantitative agreement with experimental data. The role of the angular parameters of the parametric method in the quantitative prediction of the vibrational structure of the fluorescence spectrum and changes observed in the geometry of the dinaphthylethylene molecule under excitation is determined. It is demonstrated that the polyene and acene parameters of the parametric method possess a high degree of transferability and that the models obtained are quite adequate to the real structures of the molecules under investigation. The proposed approach permits qualitative predictions and quantitative predictive calculations of the spectra of the studied molecules, as well as the spectral characteristics necessary for simulation of photochemical molecular transformations.

Calculation and interpretation of the fine structure fluorescence spectra of anthracene upon resonance excitation of vibronic states

The vibrational structure of the spectra of fluorescence of anthracene obtained upon resonance excitation of vibronic states is calculated and analyzed by the parametric method of the theory of the vibronic spectra of complex molecules. The theoretical and experimental spectra agree qualitatively with each other, which indicates that this method of modeling such spectra is efficient. The parameterization of molecular models obtained upon calculation of the ordinary fluorescence and absorption spectra is completely applicable to the calculation of the fluorescence spectra considered. A total interpretation of the spectra is presented.

Calculation and interpretation of the vibronic spectra of pyridine and trans-1,2-di(2′-pyridyl)ethylene in the second approximation of the parametric method

The structures of pyridine and dipyridylethylene molecules in an excited state and their vibronic spectra are calculated within the second approximation of the parametric method. The system of parameters obtained, including parameters of the σ and π types, ensures a quantitative agreement between the theoretical and experimental spectra of the pyridine and dipyridylethylene molecules. This agreement indicates that the proposed model is adequate to the real structure of the molecules. The parameterization is sufficiently complete and provides a means for quantitatively modeling the vibrational structure of the spectra of complex molecules containing fragments similar to those characterized by the σπ* and ππ* transitions. It is demonstrated that, after such essential substitutions of atoms in the molecules, the system of parameters of the acene and polyene fragments retains the high stability. The vibrational structure of the electronic spectra of the pyridine and dipyridylethylene molecules is interpreted, and the changes observed in the geometry of these molecules under electronic excitation are analyzed.

Analysis of the Electromagnetic Characteristics of Open Resonators Formed by a Multifocus Spherical Mirror and a Plane Mirror When the Wavelength is 1 mm

The possibility of using modern program complexes for the analysis of electromagnetic fields in a double-mirror open resonator (OR) with a focusing mirror of a complex form including an OR of an orotron in the submillimeter wavelength range is considered. The values of resonance frequencies and the distribution of the fields of the fundamental oscillation type in the OR with a focusing five-focus spherical mirror are obtained with the use of the CST Studio Suite and HFSS Ansoft program complexes. In addition, more accurate values of the Q-factor and stored energy in such ORs with the single- and double-row periodic structures on a plane mirror are obtained. Therefore, the values of the electron efficiency of an orotron can be calculated more reliably.

Parametric design and verification of inertial navigation systems

The present work is dedicated to the development of the parametric design and verification of the inertial navigation systems (INS) and the integrated navigation systems (IntNS), which enable us to estimate the accuracy of navigation systems.