DYNAMIC INFRARED SPECTROSCOPY

Attenuated total reflection (ATR) FTIR is one of the most useful tools for characterising the chemical composition and physical characteristics of polymer surfaces [53]. One useful application is the measurement of molecular orientation using polarised infrared ATR spectroscopy [54,55]. The polarised infrared ATR spectra normally include three-dimensional (e.g., machine, transverse, and thickness direction) orientational information in contrast to the polarised transmission infrared linear dichroism. In addition, band absorbance of less than 0.7 au is easily achieved, even with the strong absorption bands, because the penetration depth of ATR from sample surfaces can be adjusted to a few micrometers by changing the internal reflection element and/or the angle of incidence. If successful combination of the dynamic infrared spectroscopy and the ATR methods can be achieved, more useful dynamic orientational information can be obtained. 

Kischel, M., Kisters, D., Strobe, G., and Veeman, W.S. (1998) Dynamic infrared spectroscopy, a tool to detect hydrogen bonds in polymers Fur. Polym. J., 34, 1571. 

Anderson D T, Schwartz R L and Todd M W and Lester M I 1998 Infrared spectroscopy and time-resolved dynamics of the ortho-Hj-OH entrance channel complex J. Chem. Phys. 109 3461-73... 

We discuss the rotational dynamics of water molecules in terms of the time correlation functions, Ciit) = (P [cos 0 (it)]) (/ = 1, 2), where Pi is the /th Legendre polynomial, cos 0 (it) = U (0) U (it), u [, Is a unit vector along the water dipole (HOH bisector), and U2 is a unit vector along an OH bond. Infrared spectroscopy probes Ci(it), and deuterium NMR probes According to the Debye model (Brownian rotational motion), both... 

This comprehensive review of theoretical models and techniques will be invaluable to theorists and experimentalists in the fields of infrared and Raman spectroscopy, nuclear magnetic resonance, electron spin resonance and flame thermometry. It will also be useful to graduate students of molecular dynamics and spectroscopy. 

The vibrations of molecular bonds provide insight into bonding and stmcture. This information can be obtained by infrared spectroscopy (IRS), laser Raman spectroscopy, or electron energy loss spectroscopy (EELS). IRS and EELS have provided a wealth of data about the stmcture of catalysts and the bonding of adsorbates. IRS has also been used under reaction conditions to follow the dynamics of adsorbed reactants, intermediates, and products. Raman spectroscopy has provided exciting information about the precursors involved in the synthesis of catalysts and the stmcture of adsorbates present on catalyst and electrode surfaces. 

In the case of selective oxidation catalysis, the use of spectroscopy has provided critical Information about surface and solid state mechanisms. As Is well known( ), some of the most effective catalysts for selective oxidation of olefins are those based on bismuth molybdates. The Industrial significance of these catalysts stems from their unique ability to oxidize propylene and ammonia to acrylonitrile at high selectivity. Several key features of the surface mechanism of this catalytic process have recently been descrlbed(3-A). However, an understanding of the solid state transformations which occur on the catalyst surface or within the catalyst bulk under reaction conditions can only be deduced Indirectly by traditional probe molecule approaches. Direct Insights Into catalyst dynamics require the use of techniques which can probe the solid directly, preferably under reaction conditions. We have, therefore, examined several catalytlcally Important surface and solid state processes of bismuth molybdate based catalysts using multiple spectroscopic techniques Including Raman and Infrared spectroscopies, x-ray and neutron diffraction, and photoelectron spectroscopy. 

The objective of this study is to investigate the mechanism of propylene oxidation by a transient infrared spectroscopic technique over Rh/Al203. This technique allows simultaneous measurement of the dynamics of adsorbed species by in situ infrared spectroscopy and the product formation profile by mass spectrometry. 

I. Noda, A.E. Dowrey and C. Marcott, Characterization of polymers using polarization-modulation infrared techniques Dynamic infrared linear dichroism (DIRLD) spectroscopy. 

We focus our review on the dynamical properties of hydrogen bonds X-H Y which have been widely studied by means of infrared spectroscopy. Indeed, the infrared (IR) spectra of hydrogen bonds (H bonds) appeared to be a very useful tool because the broad stretching band vs (X-H - Y) is very informative, containing complete information on the electronic and consequently nuclear... 

Another technique that has been employed for studying certain types of changes in solids is infrared spectroscopy, in which the sample is contained in a cell that can be heated. By monitoring the infrared spectrum at several temperatures, it is possible to follow changes in bonding modes as the sample is heated. This technique is useful for observing phase transitions and isomerizations. When used in combination, techniques such as TGA, DSC, and variable-temperature spectroscopy make it possible to learn a great deal about dynamic processes in solids. 

Polymer films were produced by surface catalysis on clean Ni(100) and Ni(lll) single crystals in a standard UHV vacuum system H2.131. The surfaces were atomically clean as determined from low energy electron diffraction (LEED) and Auger electron spectroscopy (AES). Monomer was adsorbed on the nickel surfaces circa 150 K and reaction was induced by raising the temperature. Surface species were characterized by temperature programmed reaction (TPR), reflection infrared spectroscopy, and AES. Molecular orientations were inferred from the surface dipole selection rule of reflection infrared spectroscopy. The selection rule indicates that only molecular vibrations with a dynamic dipole normal to the surface will be infrared active [14.], thus for aromatic molecules the absence of a C=C stretch or a ring vibration mode indicates the ring must be parallel the surface. 

Infrared spectroscopy is the workhorse in this field, because it can quickly provide dynamical details, discriminate between different cluster sizes and phases [40], and sample a wide spectral range. It often yields valuable feedback for quantum chemical calculations. In contrast to some action spectroscopy techniques, IR absorption spectroscopy is not intrinsically size-selective. All cluster sizes generated in the expansion are observed together, and indirect methods of size assignment are needed. 

Infrared, Raman, microwave, and double resonance techniques turn out to offer nicely complementary tools, which usually can and have to be complemented by quantum chemical calculations. In both experiment and theory, progress over the last 10 years has been enormous. The relationship between theory and experiment is symbiotic, as the elementary systems represent benchmarks for rigorous quantum treatments of clear-cut observables. Even the simplest cases such as methanol dimer still present challenges, which can only be met by high-level electron correlation and nuclear motion approaches in many dimensions. On the experimental side, infrared spectroscopy is most powerful for the O—H stretching dynamics, whereas double resonance techniques offer selectivity and Raman scattering profits from other selection rules. A few challenges for accurate theoretical treatments in this field are listed in Table I. 

P. Hamm and R. M. Hochstrasser, Structure and dynamics of proteins and peptides Femto second two dimensional infrared spectroscopy, in Ultrafast Infrared and Raman Spectroscopy, Markel Dekker, New York, 2001, p. 273. 

Bisphthalonitrile monomers were cured neat, with nucleophilic and redox co-reactants, or in combination with a reactive diluent. Dynamic mechanical measurements on the resulting polymers from -150 to +300°C turn up several differences attributable to differences in network structure. Rheovibron results were supplemented with solvent extraction, differential scanning calorimetry (DSC), vapor pressure osmometry, and infrared spectroscopy to characterize the state of cure. 

An important consequence of the presence of the metal surface is the so-called infrared selection rule. If the metal is a good conductor the electric field parallel to the surface is screened out and hence it is only the p-component (normal to the surface) of the external field that is able to excite vibrational modes. In other words, it is only possible to excite a vibrational mode that has a nonvanishing component of its dynamical dipole moment normal to the surface. This has the important implication that one can obtain information by infrared spectroscopy about the orientation of a molecule and definitely decide if a mode has its dynamical dipole moment parallel with the surface (and hence is undetectable in the infrared spectra) or not. This strong polarization dependence must also be considered if one wishes to use Eq. (1) as an independent way of determining ft. It is necessary to put a polarizer in the incident beam and use optically passive components (which means polycrystalline windows and mirror optics) to avoid serious errors. With these precautions we have obtained pretty good agreement for the value of n determined from Eq. (1) and by independent means as will be discussed in section 3.2. 

R Musto, M. Abbate, G. Ragosta and G. Scarinzi, A smdy by Raman, near-infrared and dynamic-mechanical spectroscopies on the curing behaviour, molecular structure and viscoelastic properties of epoxy/anhydride networks, Polymer, 48, 3703-3716 (2007). 

Probing Metalloproteins Electronic absorption spectroscopy of copper proteins, 226, 1 electronic absorption spectroscopy of nonheme iron proteins, 226, 33 cobalt as probe and label of proteins, 226, 52 biochemical and spectroscopic probes of mercury(ii) coordination environments in proteins, 226, 71 low-temperature optical spectroscopy metalloprotein structure and dynamics, 226, 97 nanosecond transient absorption spectroscopy, 226, 119 nanosecond time-resolved absorption and polarization dichroism spectroscopies, 226, 147 real-time spectroscopic techniques for probing conformational dynamics of heme proteins, 226, 177 variable-temperature magnetic circular dichroism, 226, 199 linear dichroism, 226, 232 infrared spectroscopy, 226, 259 Fourier transform infrared spectroscopy, 226, 289 infrared circular dichroism, 226, 306 Raman and resonance Raman spectroscopy, 226, 319 protein structure from ultraviolet resonance Raman spectroscopy, 226, 374 single-crystal micro-Raman spectroscopy, 226, 397 nanosecond time-resolved resonance Raman spectroscopy, 226, 409 techniques for obtaining resonance Raman spectra of metalloproteins, 226, 431 Raman optical activity, 226, 470 surface-enhanced resonance Raman scattering, 226, 482 luminescence... 

Selected entries from Methods in Enzymology [vol, page(s)] Biomolecular vibrational spectroscopy, 246, 377 Raman spectroscopy of DNA and proteins, 246, 389 resonance Raman spectroscopy of metalloproteins, 246, 416 structure and dynamics of transient species using time-resolved resonance Raman spectroscopy, 246, 460 infrared spectroscopy applied to biochemical and biological problems, 246, 501 resonance Raman spectroscopy of quinoproteins, 258, 132. 

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