Effect of the components of the raman scattering tensor on band intensities

The Raman scattering (RS) tensor as a function of excitation radiation frequency is studied taking into account, the vibration quantum. It is shown that the corresponding asymmetric components of the tensor are described by fast converging series. Expressions are obtained for the antisymmetric and symmetric components of the RS tensor. A convenient formula is proposed for the calculation of the RS tensor and its components, where the tensor is represented as a sum of the derivative of static polarizability and the terms containing fast converging series. The formula makes it possible to avoid infinite summation. Computer experiments simulating the dependence of the intensity of RS bands and their components on the excitation frequency are carried out. Moscow State University of Building Engineering. V. I. Vernadskii Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 6, pp. 1006–1015, November–December, 1996. Translated by I. Izvekova     

Spontaneous raman spectroscopic study of the association of liquid γ-butyrolactone molecules

Self-association of γ-butyrolactone molecules in pure liquid state and in nonpolar solutions is studied by spontaneous Raman spectroscopy. The constant and the enthalpy of formation of cyclic dimers in liquid γ-butyrolactone are calculated. Ufa State Aircraft Technical University. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 6, pp. 1099–1103, November–December, 1996. Translated by L. Smolina     

Dependence of the Daman intensities of combinations and overtones on the frequency of incident light

is shown that the combined method for calculating the Raman tensor elements suggested earlier [1, 2] may be extended to calculations of the intensities of second-order Raman bands (overtones and combinations). The behavior of the intensities of the first- and second-order Raman bands is studied in a wide range of frequencies of incident light, including the resonance region. The resulting equations for the Raman scattering tensor elements are convenient from computational viewpoint; this is especially important for the intermediate frequencies, which are most difficult for calculations. Translated fromZhurnal Strukturnoi Khimii, Vol. 38, No. 3, pp. 465–469, May–June, 1997.     

Effect of structural characteristics of water on the infrared absorption and raman spectra

An analysis of band contour in the IR absorption (overtone region) and Raman spectra of water suggests that the high-frequency components of spectral bands correspond to a single continuous distribution in energy of H-bonds. A local increase in the probability density function at high frequencies, which leads to an increase in the population of states with weak hydrogen bonds, is caused by the specific behavior of the angular dependence of the energy of hydrogen bonds between water molecules. St. Petersburg State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 3, pp. 467–472, May–June, 1995. Translated by I. Izvekova     

Herzberg-teller effect and intensity distribution in the absorption and raman scattering resonance spectra of polyatomic molecules

This paper studies the influence of the Herzberg-Teller effect on the intensity distribution in one- and two-photon absorption and Raman scattering resonance spectra of substituted benzenes. A quantum mechanical analysis of the intensity distribution in the spectra of phenylacetylene and pyrazine is accomplished using the general approach suggested in [1, 2]. Due to the inclusion of vibronic coupling in the calculation, one can explain the presence of lines (as well as their combinations and overtones) arising from one-quantum excitation of nontotally symmetric vibrations. The calculated data are in good agreement with the experimental data. Significantly, the two-photon absorption spectrum of pyrazine in the region of the¹A_1g→¹B_3u long-wave singlet-singlet transition is explained only by the Herzberg-Teller effect. Saratov State Pedagogical Institute. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 2, pp. 304–309, March–April, 1995. Translated by L. Smolina     

Investigation of molecular orientation distributions by polarized raman scattering and polarized fluorescence

It is assumed that the intensity of the vibrational Raman scattering from each of the structural units (molecular segments or crystallites) in an oriented polymer solid is determined by a symmetric second-rank tensor. The distribution of orientations of the principle axes of the tensors is expanded in a series of generalized spherical harmonics, Z_lmn(θ)e^?imψe^?in?, and it is shown that relations among the coefficients in this expansion can be obtained from suitable intensity measurements using polarized radiation. If the orientation of the tensor axes within the structural unit is known (in the general case, for several Raman lines), then the coefficients M_lmn of a similar expansion for axes fixed in the units can be obtained for l, m, and n even and l ≤ 4. The limitation to even m follows from the assumption that the solid has at least orthotropic statistical symmetry but the limitations on n and l arise from the nature of the Raman effect. Some simple special cases are considered and some orientation-independent intensity sums are derived. It is shown that, with the simplifying assumption usually made, the theory of the polarized fluorescence method for determining molecular orientations is a special case of the theory for the Raman method.     

Phase transitions,conformational lability,and intermolecular interactions in alkoxycyanobiphenyls

Vibrational spectroscopy methods (IR absorption, Raman scattering, calculations) were used to study changes in molecular structures of alkoxycyanobiphenyls during phase transitions. The spectra were measured in the 33–3500 cm⁻¹ region at temperatures of 100–450 K. The temperature dependences of the IR bands that correspond to the noncharacteristic vibrations of molecular fragments between the phenyl rings and the alkyl radicals point to the conformational polymorphism of these molecules. An analysis of the Raman bands corresponding to the characteristic vibrations of the C−H bonds of alkyl radicals [q(CH)], the C−H and C−C bonds of phenyl rings [q(CH) and Q(CC)], and the CN bonds of the cyano groups [Q(CN)] suggests significant intermolecular interactions. The conformational lability and intermolecular interactions are associated with differences in molecular packing in the substances of this homologous series. Saratov State University. Institute of Solid State Physics, Rostov State University. Institute of Physics, Uzbekistan Academy of Sciences. Samarkand State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 5, pp. 814–822, September–October, 1995. Translated by I. Izvekova     

Vibrational spectra and the structure of long-chain aliphatic compounds

Polymorphism and the structure of mesomorphous states of long-chain aliphatic compounds (LAC) have been studied by vibrational spectroscopy (theory, experiment) using calorimetry, polarizing microscopy (PM), and X-ray diffraction (XRD) analysis as auxiliary methods. LAC are represented by homologous series of alkyl- and alkoxybenzoic acids, alkylcyclohexanecarboxylic acids, their completely or partially fluoroalkyl-substituted analogs, and 4-cyano-4′-(n-alkoxy)biphenyls. The studies were performed at 77–500 K. IR absorption and Raman spectra were measured at 30–4000 cm⁻¹. The compounds are characterized by conformational polymorphism. The molecules and their H-complexes undergo structural rearrangements during phase and conformational transitions. In the course of the rearrangements, alkyl and fluoroalkyl radicals (AR and FAR) are twisted, and carboxyl groups are disordered. The rearrangements dictate the structure of mesophases, which are mostly formed of H-complexes consisting of dimers, monomers, and open associates. N. G. Chernyshevskii Saratov State University. Institute of Physics, Ukrainian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 2, pp. 338–344, March–April, 1995. Translated by L. Smolina     

Vibrational spectra of volatile inorganic hydrides in the liquid state

The results of studies of IR and Raman spectra of volatile inorganic hydrides of Group IV–VI and Periods 3 and 4 elements in the liquid state are surveyed and analyzed. The mechanisms of intermolecular interactions in these liquids are discussed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 629–644, April, 1999.     

Vibrational spectra and stereochemistry of mono-and polysaccharides. II. α-anomers of D-glucose and D-galactose. Glucitol and galactitol

The IR and Raman spectra of D-glucose and D-galactose α-anomers are compared with the corresponding spectra of the related polyatomic alcohols glucitol and galactitol. Experimental data on the frequencies and modes of normal vibrations and on the contributions of normal vibrations involving particular skeletal CiOi and CiC(i+1) bonds to the potential energy distribution (PED) are compared with the results of theoretical calculations. The α-anomers of D-glucose and D-galactose with different configurations of the C4C4 and C4H4 bonds are characterized by substantially different sets of frequencies with prevailing contributions to PED from the CiOi and CiC(i+1) bonds. The similar bonds of glucitol and galactitol are also characterized by specific frequency sets. Particular CiOi and CiC(i+1) bonds have different numbers of “localized” frequencies. B. I. Stepanov Institute of Physics, Belarus Academy of Sciences. V. Tshebyatovski Institute of Low Temperatures and Structural Studies, Polish Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 3, pp. 431–442, May–June, 1995. Translated by I. Izvekova     

Variational method for calculating the anharmonic vibrations of polyatomic molecules using a combined morse-anharmonic basis taking into account the fragmentary structure of molecules

A method of variational solution of anharmonic vibration problems using a mixed Morse—anharmonic basis is proposed. The basis functions are the products of the Morse oscillator eigenfunctions for vibrations of peripheral bonds, the harmonic oscillator eigenfunctions for almost harmonic skeletal and deformation vibrations, and the anharmonic basis functions for essentially anharmonic skeletal and deformation vibrations. The anharmonic basis wave functions are taken as a linear combination of the Morse and harmonic oscillator eigenfunctions. The introduction of the combined Morse—anharmonic functions allows one to factorize the solution of a problem into a series of individual blocks according to the fragmentary structure of molecules. Volgograd Pedagogical University. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 2, pp. 231–238, March–April, 1995. Translated by I. Izvekova     

Triterpene and steroid glycosides of the genusMelilotus and their genins III. Funkioside B and protodioscin from the seeds ofMelilotus tauricus

Two steroid glycosides belonging to the furostan series — funkioside B and protodioscin — have been isolated from the seeds of the plantMelilotus tauricus (Bieb.). Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 766–770, November–December, 1994.     

Triterpene and steroid glycosides of the genusMelilotus and their genins IV. Trillin and dioscin from the seeds ofMelilotus tauricus

Two steroid glycosides belonging to the spirostan series — trillin and dioscin — have been isolated from the seeds of the plantMelilotus tauricus (Bieb.) Ser. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 770–772, November–December, 1994.     

Vibrational structure of the electron transition to the second excited singlet state of pyridine N-oxide

The vibrational structure of the electron transition to the second singlet excited state of pyridine N-oxide has been studied. The frequency of the 0–0 transition is 34502 cm⁻¹. A computer-aided technique for the assignment of the frequencies of the normal vibrations of polyatomic molecules in the excited electronic states is proposed. The frequencies of the totally symmetric vibrations of pyridine N-oxide in the second singlet electronically excited state are assigned. N. G. Chernyshevskii Saratov State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 2, pp. 350–355, March–April, 1995. Translated by I. Izvekova     

Stand-off Raman spectroscopy: a powerful technique for qualitative and quantitative analysis of inorganic and organic compounds including explosives

A pulsed stand-off Raman system has been built and optimised for the qualitative and quantitative analysis of inorganic and organic samples including explosives. The system consists of a frequency doubled Q-switched Nd:YAG laser (532 nm, 10 Hz, 4.4 ns pulse length), aligned coaxially with a 6″ Schmidt–Cassegrain telescope for the collection of Raman scattered light. The telescope was coupled via a fibre optic bundle to an Acton standard series SP-2750 spectrograph with a PI-MAX 1024RB intensified CCD camera equipped with a 500-ps gating option for detection. Gating proved to be essential for achieving high signal-to-noise ratios in the recorded stand-off Raman spectra. In some cases, gating also allowed suppression of disturbing fluorescence signals. For the first time, quantitative analysis of stand-off Raman spectra was performed using both univariate and multivariate methods of data analysis. To correct for possible variation in instrumental parameters, the nitrogen band of ambient air was used as an internal standard. For the univariate method, stand-off Raman spectra obtained at a distance of 9 m on sodium chloride pellets containing varying amounts of ammonium nitrate (0–100%) were used. For the multivariate quantification of ternary xylene mixtures (0–100%), stand-off spectra at a distance of 5 m were used. The univariate calibration of ammonium nitrate yielded R ² values of 0.992, and the multivariate quantitative analysis yielded root mean square errors of prediction of 2.26%, 1.97% and 1.07% for o-, m- and p-xylene, respectively. Stand-off Raman spectra obtained at a distance of 10 m yielded a detection limit of 174 μg for NaClO₃. Furthermore, to assess the applicability of stand-off Raman spectroscopy for explosives detection in “real-world” scenarios, their detection on different background materials (nylon, polyethylene and part of a car body) and in the presence of interferents (motor oil, fuel oil and soap) at a distance of 20 m was also investigated.     

FT-IR and FT-Raman spectroscopic study of surface species of 2-aminopyridine adsorbed by sepiolite from Anatolia

The adsorption of 2-aminopyridine by Anatolian sepiolite was investigated by Fourier-transform infrared and Fourier-transform Raman spectroscopy. The spectroscopic results indicate that 2-aminopyridine molecules adsorbed on sepiolite are coordinated to Lewis acidic centers or surface hydroxyls by H-bonding interaction through the pyridine ring nitrogen lone pairs. No physical sorbed species has been detected. Monocationic surface species has also not been detected under the conditions applied. It must be noted that the adsoiption of aminopyridine affected the hydroxyl group vibrations of sepiolite. Translated fromZhurnal Strukturnoi Khimii, Vol. 40, No. 5, pp. 981–987, September–October, 1999.     

Dynamic polarizabilities and raman intensities of CO,N2, HCl and Cl2

We have performed first-order (identical to coupled Hartree-Fock) and second-order polarization propagator calculations of the dynamic dipole polarizability tensor for the CO, N₂, HCl and Cl₂ molecules. The derivatives of the polarizability tensor with respect to the internuclear distance at the equilibrium internuclear separation are compared with related data obtained from non-resonance Raman spectra. In most cases the correlation contributions beyond the coupled Hartree-Fock approximation have a more pronounced effect on the derivatives of the polarizability tensor than on the polarizability tensor itself. At both levels of approximation we found that derivatives of the dynamic polarizability tensor with respect to the internuclear separation increase with 10–15% for variation of the frequency from 0 (static polarizability) to about 28500 cm^?1. The depolarization ratio calculated from the polarizability derivatives shows no variation with frequency in the same frequency range.     

Calculation of two-center two-electron integrals in the slaters,p,d-basis set for the Ono electron-electron potential

This paper deals with the problems of extending semiempirical MNDO methods to compounds with d-elements. The problem is solved by estimating two-center two-electron integrals (TTI) with the Ono potential modeling interaction between two electrons in a molecule. A scheme for calculating TTI is suggested which uses the expansion of the Ono potential in a series of pairwise products of spherical harmonics centered on two atoms in the molecule. The scheme is stable and efficient for calculations in arbitrary Slater basis sets (including the s,p,d-basis set) and seems to be useful for development of NDDO methods. Scientific Research Institute of Chemistry at N. I. Lobachevskii Nizhnii Novgorod State University. Translated fromZhurnul Strukturnoi Khimii Vol. 35, No. 4, pp. 24–27, July–August, 1994. Translated by L. Smolina     

Synthesis of N-aminoglycosides of the alkaloid cytisine

A series of new N-aminoglycosides of the alkaloid cytisine based on industrially available monosaccharides D-glucose, D-galactose, D-xylose, and L-arabinose was synthesized and characterized. The optimal methods for condensing and isolating the products were found. The structures and position of cytisine in the glycosides were proved by PMR spectroscopy. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 596–597, November–December, 2008.     

Novel methods for calculating the fine vibronic spectra of polyatomic molecules

Novel approximate methods for calculating the vibrational structure of the electronic spectra of polyatomic molecules—a method for the direct calculation of the overlap integrals of vibrational wave functions for the electronic states involved in a transition and a variational method for the solution of the vibrational problem for the excited states—are discussed. The methods are based on the consideration of the displacement and entanglement of normal coordinates, the quasiorthogonality of the Dushinsky transformation, and the classification of the states by total vibrational quantum numbers. Matrix perturbation theory is employed. It is shown that the accuracy of these methods compares well with the accuracy of the available “exact” techniques (the errors are ∼1 cm⁻¹ for frequency and 10% for relative intensity). At the same time, calculations by the new methods are performed more than two orders of magnitude faster than by the previously known methods. K. A. Timiryazev Agricultural Academy, Moscow. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 2, pp. 217–230, March–April, 1995. Translated by I. Izvekova