Structural vibration

Doerksen R J and Thakkar A J 1999 Structures, vibrational frequencies and polarizabilities of diazaborinines, triazadiborinines, azaboroles and oxazaboroles J. Phys. C/rem. A 103 2141... 

The spectrum of Figure lb is a fingerprint of the presence of a CO molecule, since it is different in detail from that of any other molecule. UPS can therefore be used to identify molecules, either in the gas phase or present at surfaces, provided a data bank of molecular spectra is available, and provided that the spectral features are sufficiently well resolved to distinguish between molecules. By now the gas phase spectra of most molecules have been recorded and can be found in the literature. Since one is using a pattern of peaks spread over only a few eV for identification purposes, mixtures of molecules present will produce overlapping patterns. How well mixtures can be analyzed depends, obviously, on how well overlapping peaks can be resolved. For molecules with well-resolved fine structure (vibrational) in the spectra (see Figure lb), this can be done much more successfiilly than for the broad. 

It is apparent that vibrational stresses are a function of the square of the frequency as compared with the first power of the amplitude. Thus, a structure vibrating at a high frequency but with a very small amplitude actually may... 

Ethylenediamine complexes Extraction Halide complexes structures vibrational spectra... 

Ethylenediamine complexes Extraction Halide complexes structures vibrational spectra Halides +3 state +4 state +5 state +6 state... 

Many of the sulfur-rich compounds considered in this chapter are unstable reactive species so that important properties such as geometrical structures, vibrational spectra and reaction energies are difficult to obtain experimentally and remain uncertain. In these cases, theory is particularly suited to provide the necessary complementary information to understand and interpret the experimental observations for these systems. 

The lower members of the polysulfane series with n=2-6 have been prepared as pure compounds, while all members with n values up to 35 have been detected by H-NMR spectroscopy in so-called crude sulfane [31]. The gas-phase structures of the first three members of the polysulfane series are well established from either microwave spectra (H2S2 [32], H2S3 [33]) or high-level ab initio MO calculations (H2S4 [34]). Systematic ab initio studies of the structures, vibrational frequencies and heats of formation of H2S with i up to 6 have also been reported [4, 16]. 

Since the vibrational spectra of sulfur allotropes are characteristic for their molecular and crystalline structure, vibrational spectroscopy has become a valuable tool in structural studies besides X-ray diffraction techniques. In particular, Raman spectroscopy on sulfur samples at high pressures is much easier to perform than IR spectroscopical studies due to technical demands (e.g., throughput of the IR beam, spectral range in the far-infrared). On the other hand, application of laser radiation for exciting the Raman spectrum may cause photo-induced structural changes. High-pressure phase transitions and structures of elemental sulfur at high pressures were already discussed in [1]. 

Abstract Inorganic polysulfide anions and the related radical anions S play an important role in the redox reactions of elemental sulfur and therefore also in the geobio chemical sulfur cycle. This chapter describes the preparation of the solid polysulfides with up to eight sulfur atoms and univalent cations, as well as their solid state structures, vibrational spectra and their behavior in aqueous and non-aqueous solutions. In addition, the highly colored and reactive radical anions S with n = 2, 3, and 6 are discussed, some of which exist in equilibrium with the corresponding diamagnetic dianions. 

Perturbation of structural, vibrational, and electronic features of the catalytic center by interaction with probe molecules is the most important experimental approach for understanding the accessibiUty and the reactivity of the site itself. The understanding of the system increases enormously if the experimental results are interpreted on the basis of accurate ab initio modeling. These general statements of course also hold for TS-1 [49,52,64,74-77]. Unfortunately, we do not have the space to enter into a discussion of the abim-dant computational literature published so far on TS-1 catalyst in particular and on titanoshlcates in general. The reader can find an excellent starting point in the Uterature quoted in [49,52,64,74-77,88]. 

Structure Vibration mode vexp (cm1) vn" r (cm )(int. km/mol) Isym/Iasym... 

Goovaerts, F., Vansant, E.F., De Hulsters, P. et al. (1989) Structural vibrations of acid-leached mordenites - determination of structural aluminum by wave-number and intensity analysis, J. Chem. Soc., Faraday Trans., 85, 3687. 

In a thorough work with an extensive literature survey, crystal structures, vibrational and 31P NMR spectra of several phosphine complexes of mercury(II) halides HgX2 are presented.235 In the dibenzophosphole complex (dbp)2HgBr2, Hg adopts a distorted tetrahedral coordination (rav(Hg—P) 250.2, rav(Hg—Br) 261.1pm) (cf. the related Cd complex in the previous paragraph), with slightly shorter Hg—P and Hg—Br bonds, respectively, than in the comparable... 

Conformation of a System of Three Linked Peptide Units. Biopol. 6, 1425-1436. von Carlowitz, S., H. Oberhammer, H. Willner, and J. E. Boggs. 1986. Structural Determination of a Recalcitrant Molecule (S2F4). J. Mol. Struct. 100,161-177. von Carlowitz, S., W. Zeil, P. Pulay, and J. E. Boggs. 1982. The Molecular Structure, Vibrational Force Field, Spectral Frequencies, and Infrared Intensities of CH3POF2. J. Mol. Struct. (Theochem) 87, 113-124. 

Studies on the solid-state structures, vibrational frequencies and dipole moments of tertiary phosphine chalcogenides have shown the phosphorus to be in an approximately tetrahedral environment with phosphorus-chalcogen bond lengths in-between those expected for single and double bonds.21 There has been much debate on the nature of the phosphorus-chalcogen bond in these... 

Based on structural, vibrational, and electronic features, C.-T. adducts of S-donor molecules with I2 (the most numerous) were classified in three categories 25 28 (i) Weak or medium weak characterised by a mutual perturbation... 

From these static and dynamic properties, thermodynamic functions and other properties may be calculated. All calculated values of structural, vibrational and other properties may then be compared with the corresponding observed values. 

Katsyuba, S. A., Dyson, P. J., Vandyukova, E. E., Chernova, A. V., and Vidis, A., Molecular structure, vibrational spectra, and hydrogen bonding of the ionic liquid l-ethyl-3-methyl-lH-imidazolium tetrafluoroborate, Helv. Chim. Acta, 87, 2556-2565, 2004. 

The description of bonding at transition metal surfaces presented here has been based on a combination of detailed experiments and quantitative theoretical treatments. Adsorption of simple molecules on transition metal surfaces has been extremely well characterized experimentally both in terms of geometrical structure, vibrational properties, electronic structure, kinetics, and thermo-chemistry [1-3]. The wealth of high-quality experimental data forms a unique basis for the testing of theoretical methods, and it has become clear that density functional theory calculations, using a semi-local description of exchange and correlation effects, can provide a semi-quantitative description of surface adsorption phenomena [4-6]. Given that the DFT calculations describe reality semi-quantitatively, we can use them as a basis for the analysis of catalytic processes at surfaces. 

In connection to control in dynamics I would like to take here a general point of view in terms of symmetries (see Scheme 1) We would start with control of some symmetries in an initial state and follow their time dependence. This can be used as a test of fundamental symmetries, such as parity, P, time reversal symmetry, T, CP, and CPT, or else we can use the procedure to discover and analyze certain approximate symmetries of the molecular dynamics such as nuclear spin symmetry species [2], or certain structural vibrational, rotational symmetries [3]. 

A CARS experiment has recently been done to determine the amount of vibrational and rotational excitation that occurs in the O2 (a- -A) molecule when O3 is photodissociated (81,82). Valentini used two lasers, one at a fixed frequency (266 nm) and the other that is tunable at lower frequencies. The 266 nm laser light is used to dissociate O3, and the CARS spectrum of ( (a A), the photolysis product, is generated using both the fixed frequency and tunable lasers. The spectral resolution (0.8 cm l) is sufficient to resolve the rotational structure. Vibrational levels up to v" = 3 are seen. The even J states are more populated than the odd J states by some as yet unknown symmetry restrictions. Using a fixed frequency laser at 532 nm (83) to photolyze O3 and to obtain the products 0(3p) + 02(x3l g), a non-Boltzmann vibrational population up to v" = k (peaked at v" = 0) is observed from the CARS spectrum. The rotational population is also non-Boltzmann peaked at J=33, 35 33, 31 and 25 for v" = 0,1,2,3, and k, respectively. Most of the available energy, 65-67%, appears in translation 15-18% is in rotation and 17-18% is in vibration. A population inversion between v" = 2 and 3 is also observed. 

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