Showing papers on "Infrared spectroscopy published in 1980"

Enhancement of the Infrared Absorption from Molecular Monolayers with Thin Metal Overlayers

Abstract: The infrared absorption from molecular monolayers is enhanced a factor of 20 by thin metal overlayers or underlayers with use of the attenuated-total-reflection technique. The total enhancement, including contributions from the attenuated-total-reflection geometry, is almost ${10}^{4}$. This effect is consistent with an electric field enhancement due to collective electron resonances associated with the island nature of the thin metal films.

An infrared study of water in perfluorosulfonate (Nafion) membranes

Abstract: We have studied the infrared spectra of H2O, D2O, and HDO in hydrated Nafion membranes in the sodium form. The spectrum of isotopically isolated HDO exhibits two distinct absorption bands in the OH...

Spectroscopic studies on doped polyacetylene and β-carotene

Abstract: In order to elucidate the structural details of doped polyacetylene (a highly conducting organic polymer), the optical absorption, Raman, and infrared spectra of not only trans‐(CH)x doped with iodine, AsF5, and SO3 but also β‐carotene doped with iodine and SO3 were studied. The infrared spectra of two kinds of isotopically substituted polyacetylenes (CD)x and (13CH)x doped with iodine were also observed. Analysis of the experimental results shows that upon doping each of the four vibrational branches (ν1–ν4) in the 1600–900 cm−1 region of a polyene chain splits into two groups, namely, the higher frequency group and the lower frequency one. The former group consists of the ’’gerade’’ vibrations of polyene parts which are not directly attacked by dopants but are perturbed along the chain, whereas the latter is made up of the ’’ungerade’’ vibrations of the positively charged polyene part with the doped site at its center. The Raman bands in the higher‐frequency group of ν1 (mainly the C=C stretching mode) ...

The hydrogen content of a-Ge:H and a-Si:H as determined by IR spectroscopy, gas evolution and nuclear reaction techniques

Abstract: The hydrogen content of two series of a-Ge:H and a-Si:H samples prepared by sputtering with different partial pressures of H2 in Ar has been investigated by nuclear reaction techniques, gas evolution, and infrared absorption (wagging and stretching modes).

Epoxy‐water interactions

Abstract: It has been shown that sorbed moisture plasticizes epoxy resins with a resultant depression in the glass transition temperature of the polymer. The nature of the epoxy-water interaction still requires further investigation. The equilibrium sorption and diffusion of water in a high Tg epoxy is examined. Other analytical techniques including differential scanning calorimetry, infrared spectroscopy, electron microscopy and nuclear magnetic resonance are applied to the system. Experimental results suggest that the sorbed water at low concentrations is strongly localized at specific segments or groups in the polymer. Discussion is given relative to the structure-properties of the epoxy and its possible correlation to the experimental data obtained.

Photofragmentation infrared emission studies of vibrationally excited free radicals CH3 and CH2I

Abstract: Time and wavelength‐resolved infrared fluorescence techniques are used to study the photofragmentation dynamics of CH2I2 and CH3I at the excimer laser wavelengths of 248 and 308 nm. Emission is detected from vibrationally excited CH2I and CH3 radicals as well as from the excited iodine atoms [I*(2P1/2→2P3/2)] produced in the photolysis. A complete infrared fluorescence spectrum of the highly excited CH2I radical is obtained as a function of time after the 248 nm dissociating laser pulse, providing both spectroscopic and vibrational deactivation data for the radical. Significant CH2I emission is observed at all wavelengths, indicating that excitation occurs into a very high density of states, nearing the vibrational quasicontinuum. Stronger emission features are observed in the region of the C–H stretching vibrations, the CH2 bending motion, and a combination band of these two modes. Deactivation rates for various spectral features of the highly excited CH2I radical with CH2I2 and argon are presented, alon...

Infrared Spectra of a Water‐Containing Glass

Abstract: Infrared absorption was measured on an NajO-K2O-ZnO-Al2O3-SiO2 glass with up to ∼11 wt% water. Fundamental and overtone-combination bands were observed at 1.41, 1.91, 2.22, 2.87, and 6.1 μm. Molar absorptivities were determined for the hydrated glass for H2O and OH levels using the molar absorptivity calculated for the 2.22-μm band in the as-melted glass. By this procedure the concentration of molecular water and OH groups could be determined separately. These results show that the OH content of the hydrated glass, as determined from the 2.22-μm band, is constant at >7 wt% H2O; additional H2O is attributed to molecular water only. Good agreement was found between these data and H2O/OH molecular ratios obtained from NMR.

Infrared absorption spectra of SiO2 precipitates of various shapes in silicon: calculated and experimental

Abstract: It is shown that the infrared absorption band at 1230 cm−1, observed under certain conditions of oxygen precipitation in silicon, is the LO mode of SiO2 The LO mode, which is normally infrared inactive, becomes infrared active under the condition of polarization of small (<036 μm) platelets in an appropriate dielectric matrix (silicon) Infrared absorption spectra of SiO2 particles of various shapes, imbedded in silicon, have been calculated For platelet SiO2 precipitates, the spectrum shows an absorption band at 1215 cm−1, which is reasonably close to the observed band at 1230 cm−1 For SiO2 precipitates of other shapes the spectra do not exhibit this absorption band Instead, they exhibit a slightly weaker primary absorption band at 1095 cm−1, the TO mode, and a very weak band at 1170 cm−1, which is a mixed mode of longitudinal and transverse optical phonons

Infrared refractive index of silicon.

Abstract: The infrared refractive index of silicon is determined by using the channel spectrum technique.(AIP)

Vibrational Spectroscopy of Adsorbates

Abstract: 1. Introduction.- 1.1 Vibrational Spectroscopy in Relation to Surface Science.- 1.2 Techniques in Surface Vibrational Spectroscopy.- 1.3 Vibrational Coupling and Surface Phonon Modes.- References.- 2. Theory of Dipole Electron Scattering from Adsorbates.- References.- 3. Angle and Energy Dependent Electron Impact Vibrational Excitation of Adsorbates.- 3.1 Background.- 3.2 Inelastic Electron Scattering from Oriented Molecules.- 3.3 Surface Dipole Scattering.- 3.3.1 Modes Perpendicular to the Surface.- 3.3.2 Surface Trapping in Bound State Surface Resonances.- 3.3.3 Modes Parallel to the Surface.- 3.4 Dipole Theory of One-Phonon Excitation.- 3.5 Multiple Scattering Theory of One-Phonon Excitation.- 3.6 Hydrogen Modes on W(100).- 3.6.1 Angle Dependence.- 3.6.2 Phonon Sidebands Linewidth.- 3.6.3 Impact Energy Dependence.- 3.7 Concluding Remarks.- References.- 4. Adsorbate Induced Optical Phonons.- 4.1 Background.- 4.2 A Short Review.- 4.3 Some Physical Effects.- 4.4 Hydrogen on (001) Surface of Tungsten.- 4.5 Oxygen on the (111) Surface of Nickel.- 4.6 Conclusion.- References.- 5. Inelastic Electron Tunnelling Spectroscopy.- 5.1 Background.- 5.2 IETS.- 5.2.1 Principle of IETS.- 5.2.2 Nature of Interaction.- 5.2.3 Linewidths.- 5.2.4 Sensitivity and Surface Coverage.- 5.3 Oxides.- 5.3.1 Clean Aluminium Oxide.- 5.3.2 Formic Acid on Aluminium Oxide.- 5.3.3 Clean Magnesium Oxide.- 5.3.4 Formic Acid on Magnesium Oxide.- 5.4 Comparison.- 5.4.1 Comparison with Electron Energy Loss Spectroscopy(EELS).- 5.4.2 Comparison with Surface Infrared and Raman Spectroscopies.- 5.5 Adsorbate Orientation.- 5.6 Conclusion.- References.- 6. Inelastic Molecular Beam Scattering from Surfaces.- 6.1 Background.- 6.2 Atom Scattering from Surfaces.- 6.3 Experimental Considerations.- 6.3.1 Beam Sources.- 6.3.2 Detectors.- 6.3.3 Systems.- 6.4 Data Interpretation.- 6.4.1 Selection of Scattering Conditions.- 6.4.2 Selection Rules.- 6.4.3 Scattering Kinematics.- 6.5 Experimental Results.- 6.5.1 Inelastic Studies Without Energy Resolution.- 6.5.2 Velocity Resolved Studies.- 6.5.3 Dispersion Relations.- 6.6 Conclusions and Outlook.- References.- 7. Neutron Scattering Studies.- 7.1 Theoretical Background.- Experimental Considerations.- 7.2 Applications.- 7.2.1 Sulphide Catalysts.- 7.2.2 Butane Adsorption Upon Graphite.- 7.2.3 C6H6 Adsorbed on Raney-Nickel.- 7.2.4 Collective Excitations.- 7.3 Future Considerations.- References.- 8. Reflection Absorption Infrared Spectroscopy: Application to Carbon Monoxide on Copper.- 8.1 Background.- 8.2 Physical Factors in Infrared Reflection at Metal Surfaces.- 8.3 Experimental Aspects.- 8.4 Some Applications of RAIRS.- 8.5 Spectra of CO on Copper.- 8.6 Coupling Effects in Vibrational Spectra.- 8.7 Modified Dipole Coupling Theories.- 8.8 Dipole Coupling in Islands.- References.- 9. Raman Spectroscopy of Adsorbates at Metal Surfaces.- 9.1 Background.- 9.2 Experimental Features.- 9.3 Enhanced Raman Spectra of Adsorbates on Silver Surfaces.- 9.4 Enhanced Raman Spectra of Adsorbates at Metal Other Than Silver.- 9.5 The SERS Selection Rule.- 9.6 Some Observations on the Mechanism of the Surface Raman Enhancement.- References.- 10. Vibrations of Monatomic and Diatomic Ligands in Metal Clusters and Complexes - Analogies with Vibrations of Adsorbed Species on Metals.- 10.1 Background.- 10.2 Hydrogen as Adsorbed Species or as a Ligand on Metals.- 10.3 Carbon Monoxide as Adsorbed Species and Ligands.- 10.4 Nitrogen as Adsorbed Species and as Ligands.- 10.5 Oxygen as Adsorbed Species and as Ligands.- 10.6 Nitric Oxide, NO, as Adsorbed Species and as Ligands.- 10.7 General Conclusions.- References.- 11. Coupling Induced Vibrational Frequency Shifts and Island Size Determination: CO on Pt{001} and Pt{111}.- 11.1 Background.- 11.2 CO on Pt{001}: Island Growth.- 11.3 CO on Pt{001}: "Gaseous" and Island Species.- 11.4 Conclusion.- References.

Photoacoustic Fourier Transform Infrared Spectroscopy of Solid Samples

Abstract: Fourier transform infrared spectroscopy of solids and liquids using photoacoustic detection is reported here. The advantages and disadvantages of photoacoustic detection are discussed, and comparisons of sample spectra obtained by different techniques, including photoacoustic detection, are presented and compared. Photoacoustic Fourier transform infrared spectroscopy is a promising spectroscopic method for IR analysis in cases where sample preparation is difficult.

A fourier‐transform infrared spectroscopic study of the hydrolytic stability of silane coupling agents on E‐glass fibers

Abstract: Fourier-transform (FT) infrared spectroscopy has been applied to the study the hydrothermal degradation of various coupling agents on E-glass fibers. The coupling agents studied include γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, and cyclohexyltrimethoxysilane. The amount of coupling agents on E-fibers was measured as a function of immersion time in water at 80°C. Structural changes were also followed by obtaining FT-IR difference spectra of the coupling agent on the glass fiber surface. Silanes desorb quite differently depending on the organofunctional groups. The resistance to desorption is strongly influenced by the organization of the silane interphase as well as the solubility of the silane in water.

Vibrational Spectroscopy of Molecular Liquids and Solids

Abstract: I Introduction.- Intermolecular Forces.- II Liquids.- Infrared and Raman Study of Vibrational Relaxation in Liquids.- Rotational Spectral Band Shapes in Dense Fluids.- Computer Calculation of Vibrational Band Profiles in Liquids.- Vibrational Relaxation of Hydrogen-bonded Species in Solution: Fine Structure of the ?s(XH) Band.- Experimental Study of Rotational and Vibrational Relaxation in Liquids from Investigation of the IR and Raman Vibrational Profiles.- Collision-Induced Vibrational Spectroscopy in Liquids.- Picosecond Vibrational Spectroscopy.- Vibrational Bandshapes in Viscous Liquids and Glasses.- The Study of Vibrational Relaxation by Ultrasonic and Light Scattering Techniques.- III Solids.- The Dynamics of Molecular Crystals: I. General Theory.- The Dynamics of Molecular Crystals: II. Intermolecular Potentials.- The Dynamics of Molecular Crystals: III. Infrared and Raman Intensity of Lattice Bands.- The Dynamics of Molecular Crystals: IV. Hamiltonian Perturbation Treatment.- Large Amplitude Motions in Molecular Crystals.- Raman and Infrared Lineshapes of Internal Modes in ODIC Phases.- Vibrational Band Shapes of Amorphous Solids.- Order-Disorder Phase Transitions in Solids.- The Effect of Multiphonon Processes on Vibrational Band Shapes in Molecular Solids.- Neutron Spectroscopy Studies on Rotational States in Molecular Solids.- Rotation-translation Coupling in Collective Modes of Molecular Solids and Liquids.- Participants.- Author Index.- Substance Index.

Polymerization of Organosilicones in Microwave Discharges

Abstract: Plasma polymerization of hexamethyldisiloxane (HMDSO) and hexamethyldisilazane (HMDSZ) monomers has been carried out in audio- (2 kHz, 20 kHz), radio- (5 MHz), but principally in microwave (2.45 GHz) frequency discharges. Film growth kinetics on glass and aluminum substrates have been studied by thickness and gravimetric measurements; the combined data have led to precise determinations of the film densities. The density data, in turn, provide strong evidence for a hitherto unreported structural feature, namely, that films are composed of a dense solid phase, and a thin (∼ 500 A) “oligomeric” surface layer. The solid component is about 70% denser than the equivalent “conventional” polymer, and has a marked inorganic character, as revealed clearly by infrared spectroscopy. IR analyses of polymers produced in lower frequency discharges tend to show narrow, well resolved absorption bands. In the case of 2.45 GHz films, on the other hand, bands corresponding to “inorganic” linkages tend to become bro...

Infrared spectrum of the water formaldehyde complex in solid argon and solid nitrogen

Abstract: Infrared spectra of the water formaldehyde complex in argon and nitrogen matrices have been obtained. The complex shifts of the water fundamentals clearly show that water forms a hydrogen bond with formaldehyde. HDO prefers to form a D bond, but a metastable H‐bonded complex is observed in nitrogen matrices below 20 K.

Vibrational spectra and glass structure

Abstract: Vibrational spectroscopy provides direct information about the structural arrangement of glass networks such as degree of polymerization of network-forming polyhedra and structural arrangements of silicate-germanate, silicate-borate, and related ternary glasses. The Raman spectrum provides a probe for the onset of crystallization in some glasses and for the identification of metastable phases that crystallize from glasses.

The structure of γ-aminopropyltriethoxysilane films on iron mirrors

Abstract: The structure of γ-aminopropyltriethoxysilane (γ-APS) films deposited on mechanically polished iron mirrors from aqueous solutions has been investigated using reflection-absorption infrared spectroscopy. Films formed at the natural pH of 1% aqueous solutions of γ-APS (∼10.5) were about 120 A in thickness and were composed of highly hydrolyzed oligomers characterized by infrared bands near 1550 and 1480 cm −1 . These bands were assigned to NH 2 deformation modes in amino groups that were very strongly hydrogen bonded with silanol groups to form cyclic structures. Films formed at pH = 12 were characterized by infrared bands near 1580 and 1488 cm −1 that were assigned to deformation modes of NH + 3 groups obtained by essentially complete proton transfer from silanol groups to amino groups. In all cases the as-formed films were stable in a dry environment but exposure to atmospheric humidity disrupted the strong hydrogen bonding, enabling the oligomers to condense to form polysiloxanes.

Vibrational study of and conduction mechanism in β alumina. I. Stoichiometric β alumina

Abstract: Single crystals of nonstoichiometric β alumina 11 Al2O3, (1+x)M2O3(x = 0.25 to 0.6) with M = Na, K, Tl, Ag have been studied by Raman spectroscopy between 2 and 1000 cm−1 in the 20–1400 K temperature range. Far infrared measurements have been performed between 10 and 250 cm−1. Ag(Ag)3 and (Tl)3 clusters of coupled cations have been evidenced in the low temperature spectra of Ag+ and Tl+ compounds. Ag–Ag and Tl–Tl ’’bond stretching’’ force constants were found equal, respectively, to 0.10 and 0.23 mdyn A−1. In the low temperature state, potential barriers separating sites available for cations have been found to increase at a small extent from x = 0 to x = 0.6 compounds. The temperature dependence of the low frequency Raman spectra is reported and shows that vibrational correlations between silver ions are partly responsible for the decrease of the energy necessary for the cation hopping mechanism.

A 13C NMR study of the adsorbed states of CO on Rh dispersed on Al2O3

Abstract: The results of nuclear magnetic resonance (NMR) spectroscopy have been analyzed with respect to previous infrared studies of CO adsorbed on Rh dispersed on Al2O3 to quantify the site distribution and to describe the adsorbed state. The 13C NMR spectra account for all the 13CO adsorbed on a 2.2% Rh on Al2O3 substrate. Although the spectra from the different adsorbed states of CO overlap, the line shapes may be separated into two components based on differences in the 13C spin–lattice relaxation times. These two components have been assigned to the 13CO dicarbonyl formed on single Rh atoms and to 13CO adsorbed on Rh rafts. The component attributed to the CO adsorbed on the raft sites is further separated into linear and bridged CO state contributions based on chemical shift information, yielding a quantitative distribution of the three adsorbed states of CO on Rh. The 13CO distribution is used to estimate the molar integrated intensities of the infrared spectrum of 13CO on Rh at high coverage and to determi...