Journal of Structural Chemistry

Nemukhin, A.; Grigorenko, B.; Ozhegova, N.

doi: 10.1007/BF02762647pmid: N/A

Modeling the properties of molecules isolated in low-temperature inert matrices is discussed in terms of cluster approaches. The analysis uses molecular dynamic and quantum chemical methods. Particular attention is paid to spectral features resulting from the matrix environment effects.

Perelygin, I.

doi: 10.1007/BF02762649pmid: N/A

The structure and shape of bands in the Raman vibrational spectra of polar molecules in liquids are analyzed. The possibility of using these data to examine interactions of molecules as well as their vibrational and orientational dynamics is shown.

Zelentsov, D.

doi: 10.1007/BF02762645pmid: N/A

The previously suggested approximate method for calculating the overlap integrals of vibrational wave functions is considerably improved for the purpose of maximally accurate calculation of excitation-induced mixing of normal coordinates. A general formula is obtained for all types of overlap integrals as a finite power series of the potential surface shift parameters; the coefficients are derivatives of the corresponding generating Junctions represented as polynomials of the shift vector elements of the normal coordinates and the mixing matrix. The spectra of model molecules of decatetraene and tetra- and hexadecaheptaene were calculated using the expressions derived in this work and a semiempirical parametric method for determination of excitation-induced changes in the potential surface of molecules. The calculations confirmed the high efficiency of both the parametric method and the new technique.

Espenbetov, A.; Struchkov, Yu.; Logunov, A.; Butin, B.

doi: 10.1007/BF02762668pmid: N/A

Berezm, K.; Babkov, L.

doi: 10.1007/BF02762659pmid: N/A

The electronic absorption spectrum of pyridine N-oxide vapor in the region of the third electronic transition (43,000-46,000 cm-1) was recorded. The frequencies and intensities of vibronic bands, including the 0–0 band at 43,896 cm-1, were measured An assignment of the frequencies of fundamental vibrations in the third electronically excited state is suggested The matrices of rotation and shift of normal coordinates due to electronic excitation are calculated, and the vibronic spectrum of pyridine N-oxide is interpreted on the basis of these matrices.

Godunov, I.; Abramenkov, A.; Pupyshev, V.

doi: 10.1007/BF02762652pmid: N/A

The results of the analysis of the fluorescence excitation spectrum of trans-hexafluorobiacetyl published earlier are revised. New values of torsion frequencies and potential barriers of internal rotation of the CF3 group in the ground and excited states of the molecule are obtained. A procedure for calculating the probabilities of torsional vibronic transitions of molecules is described.

Petrov, V.; Petrova, V.; Giricheva, N.; Girichev, G.

doi: 10.1007/BF02762665pmid: N/A

Apostolova, E.; Tulub, A.

doi: 10.1007/BF02762648pmid: N/A

A method for solving the vibrational problem by using an effective energy operator containing Morse potentials and new model atom approximations is developed. The approach is explained by reference to the trifluoromethylacetylene molecule where the model atom is a CCC or CC atomic group. Using certain assumptions for parameters in the spectrum, we managed to confirm the known experimental result of bond strengthening of the terminal hydrogen atom when the CC bond order increases and to predict the CH bond energy (462.5±4.6 kJ/mole). This procedure seems to be also effective for more complex adsorption problems where the model atom is a crystal. Given that the surface effect is predicted by the parameters of the method, the corresponding model energy operator is constructed. With appropriate spectral data, the approach guarantees very accurate estimations of adsorption bond energies.

Piottukh-Peletskii, V.; Derendyaev, B.; Bogdanova, T.

doi: 10.1007/BF02762661pmid: N/A

The results of identification of five-, six-, and seven-node fragments by the IR spectra of compounds are characterized by quantitative parameters: probability, reliability, and types of fragments. This analysis is carried out using the database containing more than 11,000 complete IR spectra and structures of organic compounds. It is analyzed how the fractions of correct fragments in the search result depend on the threshold occurrence and nonrandomness of fragment selection. Examples of statistical reliability of the revealed fragments are given.

Balashov, S.; Ivanov, I.; Karpov, V.; Korotaev, O.; Shchanov, M.

doi: 10.1007/BF02762654pmid: N/A

The effect of external pressure on the fluorescence spectra of perylene in n-octane at helium temperatures is investigated. It is shown that isobaric treatment of the sample considerably decreases the electronphonon interaction of the impurity molecules with the surroundings and gives rise to doublet structure of the spectra. The latter is explained in terms of the two-well adiabatic potential model