Calculation of Normal Vibrations and Interpretation of the Quasiline Spectra of Tetraazachlorin

Quasiline fluorescence and fluorescence-excitation spectra of tetraazachlorin and its N-deuterated derivative in n-octane at 77 K have been investigated and the frequencies of the normal vibrations for the electronic states S ₀ and S ₁ have been determined. Calculation of the normal vibrations of these molecules has been done and used to interpret the experimental data. Based on the results of analysis of the intensities in the spectra, the change in the structure of the molecule in the electronic state S ₁ is discussed.     

Vibrational spectroscopy and DFT calculations of di‐amino acid cyclic peptides. Part I: cyclo(Gly‐Gly), cyclo(L‐Ala‐L‐Ala) and cyclo(L‐Ala‐Gly) in the solid state and in aqueous solution

Investigations of the vibrational spectra of cyclo(Gly‐Gly), cyclo(L‐Ala‐L ‐Ala) and cyclo(L ‐Ala‐Gly) are reported. Raman scattering and Fourier transform infrared (FTIR) spectra of solid‐state and aqueous protonated samples, as well as their corresponding N‐deuterated isotopomers, have been examined. In addition, density functional theory (DFT) (B3‐LYP/cc‐pVDZ) calculations of molecular structures and their associated vibrational modes were carried out. In each case, the calculated structures of lowest energy for the isolated gas‐phase molecules have boat conformations. Assignments have been made for the observed Raman and FTIR vibrational bands of the cyclic di‐amino acid peptides (CDAPs) examined. Raman polarization studies of aqueous phase samples are consistent with C₂ and C₁ symmetries for the six‐membered rings of cyclo(L‐Ala‐L‐Ala) and cyclo(L‐Ala‐Gly), respectively. There is a good correlation between experimental and calculated vibrational bands for the three CDAPs. These data are in keeping with boat conformations for cyclo(L‐Ala‐L‐Ala) and cyclo(L‐Ala‐Gly) molecules, predicted by the ab initio calculations, in both the solid and aqueous solution states. However, Raman spectroscopic results might infer that cyclo(L‐Ala‐Gly) deviates only slightly from planarity in the solid state. The potential energy distributions of the amide I and II modes of a cis‐peptide linkage are shown to be significantly different from those of the trans‐peptides. For example, deuterium shifts have shown that the cis‐amide I vibrations found in cyclo(Gly‐Gly), cyclo(L‐Ala‐L‐Ala), and cyclo(L‐Ala‐Gly) have larger N‐H contributions compared to their trans‐amide counterparts. Compared to trans‐amide II vibrations, cis‐amide II vibrations show a considerable decrease in N H character. Copyright © 2009 John Wiley & Sons, Ltd.     

Calculation of Normal Vibrations of the Tetraazaporphin Molecule and Interpretation of Quasiline Spectra

Quasiline fluorescence and fluorescence-excitation spectra of tetraazaporphin and its N-deuterated derivative in n-octane at 77 K have been investigated, and the frequencies of normal vibrations in electronic states S ₀ and S ₁ have been determined. Calculation of normal vibrations of these molecules has been done and, on its basis, the experimental data are interpreted. It is shown that in the spectra, predominantly the totally symmetric vibrations of type A _g symmetry of the point D _2h symmetry group are active. Some activation of the nontotally symmetric B _1g vibrations in the fluorescence-excitation spectra is explained by the nonadiabatic interaction of the vibrational sublevels of the excited electronic state S ₁ with the purely electronic level S ₂.     

High‐resolution stimulated Raman spectroscopy and analysis of the ν2 and ν3 bands of C2H4

The high‐resolution stimulated Raman spectra of the ν₂ and ν₃ bands of C₂H₄ have been recorded and analyzed separately by means of the tensorial formalism developed in Dijon and Reims for X₂Y₄ asymmetric‐top molecules. For the ν₂ band, a total of 191 lines were assigned and fitted. We obtained a global root mean square deviation of 1.86 × 10^{− 3} cm^{− 1}. For the ν₃ band analyzed in interaction with the ν₆ infrared band, a total of 185 lines were assigned and fitted. We obtained a global root mean square deviation of 1.29 × 10^{− 3} cm^{− 1}. Both analyses lead to very satisfactory synthetic spectra. Copyright © 2013 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the uranyl mineral natrouranospinite (Na2,Ca)[(UO2)(AsO4)]2· 5H2O

Raman spectra of natrouranospinite complemented with infrared spectra were studied and related to the structure of the mineral. Observed bands were assigned to the stretching and bending vibrations of (UO₂)²⁺ and (AsO₄)³⁻ units and of water molecules. U O bond lengths in uranyl and O H···O hydrogen bond lengths were calculated from the Raman and infrared spectra. Copyright © 2009 John Wiley & Sons, Ltd.     

EELS of methane physisorbed on NaCl(100)

EELS spectra of CH₄, CD₄ and CH₂D₂ physisorbed on NaCl(100) at 40 K are presented. For the clean NaCl surface, increasing the incident beam energy to the 30 to 50 eV range is sufficient to overcome charging effects. However, when adsorbate is present charging prevents extended signal averaging. All methane modes appear to contribute to the EELS spectra. Loss peaks corresponding to adsorbate vibrations are very broad (400 to 600 cm⁻¹, FWHH), the low resolution being probably due to a combination of effects including surface disorder, scattering of electrons by gas phase molecules and charging effects.     

Raman spectroscopic study of the uranyl mineral metauranospinite Ca[(UO2)(AsO4)]2·8H2O

Raman spectra of metauranospinite Ca[(UO₂)(AsO₄)]₂·8H₂O complemented with infrared spectra were studied. Observed bands were assigned to the stretching and bending vibrations of (UO₂)²⁺ and (AsO₄)³⁻ units and of water molecules. U O bond lengths in uranyl and O H···O hydrogen bond lengths were calculated from the Raman and infrared spectra. Copyright © 2009 John Wiley & Sons, Ltd.     

Lineshape analysis of stimulated Raman spectra of the near‐nozzle region of free jet expansions

An anomalous lineshape of stimulated Raman spectra obtained from the region very close to the nozzle of supersonic pulsed expansions of nitrogen is presented. High‐resolution Raman spectra of the Q branch of the fundamental vibration mode of N₂ have been recorded from two different nitrogen expansions at T₀ = 295 K and P₀ = 1.5–3.5 bar, the lasers crossing the jet axis in the range z/D = 0.25–1.25, where D is the effective nozzle diameter. The combination of Doppler shifts and strong gradients of density and temperature in the near‐nozzle region yield an inhomogeneous broadening and a double peak structure of the recorded Raman line profiles. The comparison of the experimental results with the simulation of the Raman spectrum from this region provides valuable information about the near‐nozzle flow field. The lineshape described here is different from another reported previously in the literature, which is based on a depletion of the density of free molecules on the axis due to condensation. Copyright © 2009 John Wiley & Sons, Ltd.     

Theory of the effect of intermolecular interactions on the Raman spectra of liquid CHCl3 and CFCl3

A theory of weak intermolecular interactions is presented which indicates how association in the liquid state can manifest itself in vibration spectra. The theory is applied in this case to CHCl₃ and CFCl₃. The calculations predict which bands are most sensitive to the effects of intermolecular interaction. Previous experimental observations on the behaviour of the a ₁ vibrations of these molecules are reproduced. The calculations also predicted new features in the behaviour of the degenerate vibrations which were confirmed experimentally.

The method lends itself to the study of solvent effects on vibration spectra in general.     

Raman and infrared study of phyllosilicates containing heavy metals (Sb,Bi): bismutoferrite and chapmanite

The kaolinite‐like phyllosilicate minerals bismutoferrite BiFe³⁺₂Si₂O₈(OH) and chapmanite SbFe³⁺₂Si₂O₈(OH) have been studied by Raman spectroscopy and complemented with infrared spectra. Tentatively interpreted spectra were related to their molecular structure. The antisymmetric and symmetric stretching vibrations of the Si O Si bridges, δ SiOSi and δ OSiO bending vibrations, ν (Si O_terminal)⁻ stretching vibrations, ν OH stretching vibrations of hydroxyl ions, and δ OH bending vibrations were attributed to the observed bands. Infrared bands in the range 3289–3470 cm⁻¹ and Raman bands in the range 1590–1667 cm⁻¹ were assigned to adsorbed water. O H···O hydrogen‐bond lengths were calculated from the Raman and infrared spectra. Copyright © 2009 John Wiley & Sons, Ltd.     

Structural and crystallization behavior of (Ba,Sr)TiO3 borosilicate glasses

Various glass samples were prepared by melt quench technique in the glass system [(Ba_{1? x} Sr _x ) TiO₃]–[2SiO₂–B₂O₃]–[K₂O] doped with 1?mole% of La₂O₃. Infrared spectra show the number of absorption peaks with different spliting in the wave number range from 450 to 4000?cm^?1. Absorption peaks occurs due to asymetric vibrational streching of borate by relaxation of the bond B–O of trigonal BO₃. Raman spectra show the Raman bands due to ring-type metaborate anions, symmetric breathing vibrations BO₃ triangles replaced by BO₄ tetrahedra, and symmetric breathing vibrations of six-member rings. The differential thermal analysis of a glass sample corresponding to composition x?=?0.0 shows crystallization temperature at 847°C and glass transition temperature at 688°C. X-ray diffraction (XRD) pattern of glass ceramic samples shows the major crystalline phase of BaTiO₃ whereas pyrochlore phases of barium titanium silicate. Scanning electron micrographs confirm the results of XRD as barium titanate is major crystalline phase along with pyrochlore phase of barium titanium silicate.     

The analysis of pH‐dependent protonated conformers of 1‐hydroxyethylidene‐1,1‐diphosphonic acid by means of FT‐Raman spectroscopy,multivariate curve resolution and DFT modelling

1‐Hydroxyethylidene‐1,1‐diphosphonic acid (HEDP) solutions in the pH range 0.98–13.00 were analysed using FT‐Raman spectroscopy and ³¹P and ²³Na NMR spectroscopy. Vibrational bands for different protonated species were observed in the Raman spectra, whereas only a single NMR signal that shifted with pH was observed for all samples over the entire pH range. No significant shift in the ²³Na NMR signal was observed, confirming that formation of Na⁺(aq) complexes did not take place; hence, no interference with the different protonated forms of HEDP occurred. Vibrational bands were assigned using density functional theory(DFT)‐calculated spectra of the most likely conformers in solution. Multivariate curve resolution was performed on the Raman spectra in the region containing the PO stretching vibrations to determine the number of protonated species formed over the entire pH range. Chemometric analysis compares very favourably with the experimental species distribution diagram which was generated using the reported log K_H values. Copyright © 2009 John Wiley & Sons, Ltd.     

Spectroscopy and dissociation of sulfuryl halides SO2X2 (X=F,Cl)

The spectroscopy and dissociation of the sulfuryl halides SO₂F₂ and SO₂Cl₂ have been studied in detail using ab initio methods. The possibility of various dissociation channels has been explored taking into account that the fragmented atoms and molecules can stay in their ground state only. An interesting pattern was observed in their dissociation energy spectra for the dissociation channels. The singlet potential energy surfaces for the exit channels of these molecules have been analysed. The release of halogen molecules after dissociation is discussed from an industrial point of view. Finally, the enthalpy of formation of these molecules was computed using the ab initio results. Our results agree very well with the experimental values available.     

Overtone spectroscopy of benzaldehyde

The vibrational overtone spectra of aryl and alkyl C-H stretch vibrations in benzaldehyde have been studied using conventional IR and thermal lensing technique at room temperature. The stretching vibrational frequencyω _e, anharmonicity constantω _e x _e and the dissociation energies of the two C-H bonds have been calculated. The bond length of C-H bond in aryl position has been estimated.     

Effect of an aliphatic spacer group on the adsorption mechanism of phosphonodipeptides containing N-terminal glycine on the colloidal silver surface

This study presents the complete solid-state vibrational assignments for a series of five zwitterionic phosphonodipeptides containing an N-terminal glycine: L -Gly-L -CH(Me)-PO₃H₂ (G1), L -Gly-C(Me,Me)-PO₃H₂ (G2), L -Gly-L -CH(Et)-PO₃H₂ (G3), L -Gly-C(Me,Et)-PO₃H₂ (G4), and L -Gly-L -CH(iBu)-PO₃H₂ (G5). The assignments are based primarily on Fourier-transform Raman spectra (FT-RS) and Fourier-transform infrared spectra (FT-IR) spectra, as well as density functional theory (DFT) calculations at the B3LYP; 6-31 + + G** level of theory. Existing literature data are also taken into consideration. The surface geometry of these molecules on a colloidal silver surface was also determined by observing the wavenumber, width, and relative intensity changes of enhanced bands in their surface-enhanced Raman scattering spectra. It is proposed that G1 mainly adsorbs onto the colloidal silver particles through the phosphonate terminus, whereas the PO bond in G3 and G5 assists in the interaction of these molecules with the silver surface. G3 interacts with Ag mainly via α-methlyalanine and the amide bond. It is also shown that the amide bond and glycine backbone are involved in the adsorption of G3 on the silver nanoparticles. In addition, the differences recorded for G4 and G5 SERS spectra are mainly due to interactions between the silver surface and the amine group and N- and P-terminus, respectively, and are manifestations of the characteristic vibrations of these groups. Copyright © 2008 John Wiley & Sons, Ltd.     

Strong quadrupole interaction of light with molecules and its manifestation in surface-enhanced hyper-Raman scattering spectra

The possibility of the giant enhancement of hyper-Raman scattering by molecules adsorbed on rough metal surfaces is demonstrated. The theory is based on the qualitative consideration of electromagnetic field enhancement near some model rough surfaces and individual irregularities, as well as on the quantum-mechanical features of dipole and quadrupole interactions of light with molecules (as in the theory of surface-enhanced Raman scattering), proposed by the author. A consideration of symmetric molecules makes it possible to obtain selection rules for surface-enhanced hyper-Raman scattering (SEHRS) spectra and establish such a regularity as the occurrence of strong forbidden lines (which are due to totally symmetric vibrations); these lines are transformed according to unitary irreducible representation in molecules with the symmetry groups C _nh , D, and higher. An analysis of the data in the literature for trans-1,2-bis (4-pyridyl)ethylene and pyridine molecules shows that their spectra can be explained in terms of the dipole-quadrupole theory of SEHRS. At the same time, the analysis of the SEHRS spectra of pyrazine revealed the presence of strong forbidden bands due to totally symmetric vibrations. This finding substantiated the proposed theory, which makes it possible to interpret the entire spectrum in detail. These results are in good agreement with the general mechanism of the optical effects enhanced by molecules adsorbed on metal surfaces, which was developed by the author.     

Vibrational spectroscopy and DFT calculations of N,N′‐dicyclohexylcarbodiimide

Infrared (IR) and Raman spectra were obtained for N,N′‐dicyclohexylcarbodiimide (DCC) in the solid state and in CHCl₃ solution. Structures and vibrational spectra of isolated, gas‐phase DCC molecules with C₂ and C_i symmetries, computed at the B3‐LYP/cc‐pVTZ level, show that the IR and Raman spectra provide convincing evidence for a C₂ structure in both the solid state and in CHCl₃ solution. Using a scaled quantum‐chemical force field, these density functional theory calculations have provided detailed assignments of the observed IR and Raman bands in terms of potential energy distributions. Comparison of solid‐state and solution spectra, together with a Raman study of the melting behaviour of DCC, revealed that no solid‐state effects were evident in the spectra. Copyright © 2010 John Wiley & Sons, Ltd.     

Er3+及Er3+/Yb3+共掺铋酸盐玻璃光谱性质研究

制备了Er³⁺及Er³⁺/Yb³⁺共掺铋酸盐玻璃，测试了样品的吸收光谱、荧光光谱.应用Judd-Oflet理论计算了Er³⁺在铋酸盐玻璃中的光谱强度参数，分别为Ω₂=(5.47—2.92)×10^-20cm²，Ω₄=(2.16—1.22)×10^-20cm², 关键词： 3+')" href="#">Er³⁺ 铋酸盐玻璃 3+/Yb³⁺共掺')" href="#">Er³⁺/Yb³⁺共掺 光谱性质     

The numerical determination of dipole hyperpolarizabilities

The paper is devoted to calculations of the contour shapes in the infra-red and Raman spectra of the 1 : 1 and 1 : 2 type complexes of ordinary and heavy water with two organic bases, dioxane and dimethyl sulphoxide, by means of a computer. The calculations have been made using the mathematical formalism developed in the previous papers of this series which takes into account the coupling between two stretching vibrations of the water molecule and the overtone of its bending vibration for a set of the liquid molecules variously perturbed by non-equal H-bonds. The basic parameters of the model are obtained from the spectra of HOD molecules involved in the same complex as the one considered, and from empirical correlations discussed in the previous papers. Starting from a set of parameters determined in this manner we calculate three spectra simultaneously for each of the above-mentioned complexes, namely the infra-red spectrum and the isotropic and anisotropic components of the Raman spectrum. Every spectrum is composed of three contours belonging to the overtone of the bending vibrations, and also to the in-phase and out-of-phase stretching vibrations respectively. These contours are asymmetrical and have different half-widths, maximum frequencies and intensities in all three types of spectra. The model demonstrates the inadequacy of the widespread interpretation of such spectra in terms of the symmetric and antisymmetric vibrations of undistorted water molecules characterized by the symmetry C _2v . Good agreement between calculated and experimental spectra is considered to provide strong evidence of the fluctuation model.