Showing papers on "Infrared spectroscopy correlation table published in 2000"

Reflection Absorption Infrared Spectroscopy and the Structure of Molecular Adsorbates on Metal Surfaces

Abstract: Infrared (IR) spectroscopy is widely used to identify molecular adsorbates that form on metals in the course of surface chemical reactions. Because IR spectroscopy is one of the few surface-sensitive probes that provide molecule-specific information without perturbing the chemisorbed state, there is great interest in extracting as much structural information from the spectra as possible. The various ways IR spectroscopy is used to determine the structure of molecular adsorbates, from strictly qualitative interpretations based on symmetry selection rules to the use of ab initio electronic structure calculations to predict the IR spectrum of a chemisorbed molecule, are reviewed.

Reactions of substituted aromatic hydrocarbons with the Si(001) surface

Abstract: The interactions of toluene, para-xylene, meta-xylene and ortho-xylene with the (001) surface of silicon have been investigated using Fourier-transform infrared spectroscopy Infrared spectra show that these methyl-substituted aromatic hydrocarbons are chemisorbed and oriented on the Si(001) surface at both 110 and 300 K Peaks in the Si–H stretching region indicate that some dissociation occurs upon adsorption Comparisons of infrared spectra of these molecules with deuterated and nondeuterated methyl groups reveal that the major source of decomposition is likely from C–H cleavage of the substituent groups, leaving the ring intact Additionally, the striking similarity of the infrared spectra of benzene, toluene and the xylene isomers suggests that the methyl-substituted aromatic rings interact with the Si(001) surface in much the same way as benzene Differences in relative peak intensity point to the possibility that the methyl substituent groups may steer the ring into different ratios of specific bon

Saturated-absorption spectroscopy with low-power difference-frequency radiation.

Abstract: We report high-resolution saturated-absorption spectra recorded by use of a few microwatts of radiation generated in a single pass by difference-frequency mixing. These results were obtained without the use of buildup cavities for the nonlinear mixing or for the saturation spectroscopy. We show high-quality saturated-absorption signals for the fundamental rovibrational band of CO2 near 4.3 µm. Convenient sources and frequency-conversion devices open new possibilities for sub-Doppler spectroscopy in the infrared.

Infrared Vibration-Rotation Spectroscopy: From Free Radicals to the Infrared Sky

Abstract: Calculation of Vibration-Rotation Energy Levels: Symmetry, Transformations, Open-Shell Molecules. Effective Hamiltonians for Flexible or Floppy Molecules. Rovibrational Line Intensities and Lineshapes: Linear and Non-Linear Spectroscopy. The Experimental Measurement of Infrared Spectra. Analysis of the Vibration-Rotation Bands of Linear Molecules. Analysis of Symmetric and Spherical Rotor Spectra. Asymmetric Rotor Bands. Electric and Magnetic Resonance Spectroscopy. Laser Spectroscopy of Free Radicals, Ions and Weakly Bound Molecules. Spectroscopy of the Earth's Atmosphere: Interplay Between High-Resolution Laboratory Spectroscopy and Remote Sensing. Astrophysical Spectra. Indexes.

Infrared and Raman Spectroscopy

Abstract: The article contains sections titled: 1. Introduction 2. Techniques 2.1. Fourier Transform Infrared Technique 2.2. Dispersive and Fourier Transform Raman Techniques 3. Basic Principles of Vibrational Spectroscopy 3.1. The Vibrational Spectrum 3.2. QuantitativeAnalysis 3.3. The Symmetry of Molecules and Molecular Vibrations; SelectionRules 4. Interpretation of Infrared and Raman Spectra of Organic Compounds 4.1. The Concept of Group Frequencies 4.2. Methyl and Methylene Groups 4.3. Alkene Groups 4.4. Aromatic Rings 4.5. Triple Bonds and Cumulated Double Bonds 4.6. Ethers, Alcohols, and Phenols 4.6.1. Ethers 4.6.2. Alcohols and Phenols 4.7. Amines, Azo, and Nitro Compounds 4.7.1. Amines 4.7.2. Azo Compounds 4.7.3. Nitro Compounds 4.8. CarbonylCompounds 4.8.1. Ketones 4.8.2. Aldehydes 4.8.3. Carboxylic Acids 4.8.4. Carboxylate Salts 4.8.5. Anhydrides 4.8.6. Esters 4.8.7. Lactones 4.8.8. Carbonate Salts 4.8.9. Amides 4.8.10. Lactams 4.9. Sulfur-Containing Compounds 4.9.1. Thiols 4.9.2. Sulfides and Disulfides 4.9.3. Sulfones 4.10. Computer-Aided Spectral Interpretation 5. Applications of Vibrational Spectroscopy 5.1. Infrared Spectroscopy 5.1.1. Transmission Spectroscopy 5.1.2. External Reflection Spectroscopy 5.1.3. Internal Reflection Spectroscopy 5.1.4. Diffuse Reflection Spectroscopy 5.1.5. Emission Spectroscopy 5.1.6. Photoacoustic Spectroscopy 5.1.7. Chromatography/Fourier Transform Infrared Spectroscopy 5.1.8. Thermogravimetry/Fourier Transform Infrared Spectroscopy 5.1.9. Vibrational Circular Dichroism 5.2. Raman Spectroscopy 5.3. Fourier Transform Infrared and Raman Microspectroscopy 5.4. Time-Resolved FT-IR and FT-Raman Spectroscopy 5.5. Vibrational Spectroscopic Imaging 5.6. Infrared and Raman Spectroscopy of Polymers 6. Near-Infrared Spectroscopy 6.1. Comparison of Mid-Infrared and Near-Infrared Spectroscopy 6.2. Applications of Near-Infrared Spectroscopy

Infrared Spectroscopy in Analysis of Polymers and Rubbers

Abstract: The infrared spectrum of a polymer or rubber is a profile of its absorption characteristics plotted against infrared wavenumber (or frequency). It is generated when infrared radiation interacts with the molecular moieties that constitute the polymer or rubber material. It is a distinctive property (a “fingerprint”) of the polymer or rubber sample in the form, manner and environment in which it is being examined. It is based on the absorption of infrared radiation at frequencies that match those of the normal modes of vibration within the macromolecule. These absorption features are characteristic of the molecular configuration, sequencing and conformation, and state of order. Absorptions by internal vibrations predominate in the mid-infrared region (ca. 4000–400 cm−1); they involve a few selected atoms in a molecular (functional) grouping, which is a sub-set of those constituting the macromolecule. External vibrations, such as lattice vibrations, which involve segments of macromolecules in crystalline regions, tend to occur at low wavenumbers (<400 cm−1). The intensity of an absorption band is, to a first approximation, proportional to the number density of vibrating species giving rise to that band. The intensity of an absorption band is related to the dipole moment change associated with the molecular vibration; if it is large then the band intensity will be high. Infrared spectroscopy is highly specific. For some quantitative analyses, it can be very precise and sensitive (<0.1%). It is complemented with Raman spectroscopy, for which the selection rules are different and relate band intensity to the change of polarizability occurring during a molecular vibration. Infrared spectroscopy can be used to identify and analyse the molecular structure, composition, order and morphology, both qualitatively and quantitatively, of polymers, copolymers and rubbers and their products. However, for heavily filled and plasticized formulations the spectral interferences may be too high to allow direct or adequate interpretation of a spectrum, and separation of the components will be necessary for unambiguous identifications.

Infrared spectroscopic study of molecular hydrogen bonding in chiral smectic liquid crystals

Abstract: We report the use of Fourier-transform infrared (IR) spectroscopy to probe intermolecular and intramolecular hydrogen bonding in thermotropic liquid-crystal phases. Infrared spectra of aligned smectic liquid crystal materials vs temperature, and of isotropic liquid-crystal mixtures vs concentration were measured in homologs both with and without hydrogen bonding. Hydrogen bonding significantly changes the direction and magnitude of the vibrational dipole transition moments, causing marked changes in the IR dichroic absorbance profiles of hydrogen-bonded molecular subfragments. A GAUSSIAN94 computation of the directions, magnitudes, and frequencies of the vibrational dipole moments of molecular subfragments shows good agreement with the experimental data. The results show that IR dichroism can be an effective probe of hydrogen bonding in liquid-crystal phases.

Infrared Spectrum and Group Theoretical Analysis of the Vibrational Modes of Carbonyl Sulfide

Abstract: Carbonyl sulfide (OCS) is an excellent sample for infrared spectroscopy and normal mode analysis experiments in the physical chemistry laboratory. Students use HyperChem to calculate the vibrational spectrum and visualize vibrational motions; the infrared activities of the vibrational modes are then predicted using group theory. Because all fundamental, overtone, and combination bands of OCS are infrared active, the spectrum of OCS has many features for students to assign. The rotational substructure of the fundamental transitions is also partially resolved and can be explained in terms of the selection rules for parallel and perpendicular transitions. Finally, we describe the unique observation of a hot band transition in the infrared for the ν2 bending mode and compare its intensity to the relative population predicted from the Boltzmann distribution.

Resolution of overlapping spectra by wavelength modulation spectroscopy

Abstract: RESOLUTION OF OVERLAPPING SPECTRA BY WAVELENGTH MODULATION SPECTROSCOPY Audra Michiele Bullock Old Dominion University, 2000 Director Dr. Amin N. Dharamsi Wavelength modulation absorption spectroscopy is a highly sensitive, nonintrusive technique for probing gaseous species, which employs the well-known principles of modulation spectroscopy in a novel way. With this technique, parameters such as velocity, density, and temperature can be measured with a high degree of precision. The research presented here shows that wavelength modulation is a convenient means of increasing the sensitivity of an absorption spectroscopy measurement because it allows for harmonic detection. The focus of the dissertation is resolution of overlapping spectra by harmonic detection and the advantages gained by performing detection at the higher harmonics, e.g., sixth and eighth. Additionally, it is shown that the higher harmonic detection orders can be used to identify transition line shape profiles as well as absorption line parameters. A study of the line shape profile for the oxygen A-band transitions is presented. The results of this study indicate that oxygen exhibits collisional narrowing on the order of 0.006 cm' 1 atm' 1 in this near infrared atmospheric band. Other general characteristics of absorption signals obtained by employing wavelength modulation spectroscopy with harmonic detection are discussed along with their corresponding applications. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. This dissertation is dedicated to my parents, Dwight and Debbie Bullock. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.

Computational and Experimental Infrared Spectra of 1,4-Dinitropiperazine and Vibrational Mode Assignment

Abstract: The IR spectra of both solid and matrix-isolated 1,4-dinitropiperazine (p-DNP) were obtained. The results indicate that 1,4-dinitropiperazine at 11 K is a mixture of three chair conformer structure...