Abstract: Gallium nitride was studied by Raman scattering and x-ray-absorption spectroscopy up to 60 GPa. A high-pressure structural phase transition was observed in gallium nitride at 47 GPa by means of Raman scattering and x-ray-absorption spectroscopy. We also report the direct determination of the bulk modulus ${\mathit{B}}_{0}$ of this compound (245 GPa). Gr\"uneisen parameters of the four observed phonon modes were established. The transition pressure is compared with existing calculations.

Abstract: We investigate the quantum-mechanical noise in spectroscopic experiments on ensembles of N two-level (or spin-1/2) systems where transitions are detected by measuring changes in state population. By preparing correlated states, here called squeezed spin states, we can increase the signal-to-noise ratio in spectroscopy (by approximately ${\mathit{N}}^{1/2}$ in certain cases) over that found in experiments using uncorrelated states. Possible experimental demonstrations of this enhancement are discussed.

Abstract: The magnetic and morphological properties of fine Fe particles have been studied. Ultrafine particles of Fe were prepared using a vapor deposition technique under an argon atmosphere. The argon pressure was varied from 0.5 to 8 Torr during evaporation, and samples with a median diameter in the range 50--200 \AA{} were obtained having a log-normal distribution. The dependence of magnetic properties on particle size and temperature (10 KT300 K) were studied using superconducting-quantum-interference-device magnetometry and M\"ossbauer spectroscopy. Samples with particle diameter below 90 \AA{} showed a superparamagnetic behavior below room temperature. The saturation magnetization of the particles varied from 25 to 190 emu/g, with the higher values corresponding to larger particles. For these larger particles, a coercivity of 1.05 kOe was obtained at room temperature. The magnetic and structural data suggested a core-shell type of structure, where the core consists of metallic Fe and the shell is composed of Fe oxides.

Abstract: Theory of polymer characterization vibrational spectroscopy of polymers experimental IR spectroscopy of Polymers applications of IR spectroscopy to polymers Raman spectroscopy of polymers high-resolution NMR spectroscopy of polymers in solution special editing techniques for high-resolution NMR spectroscopy of polymers high-resolution NMR spectroscopy of solid polymers applications of high-resolution solid-state NMR spectroscopy of polymers NMR relaxation spectroscopy of polymers NMR imaging of polymeric materials.

Abstract: Transmission infrared (IR) spectroscopy, either dispersive or Fourier transformed (FTIR), has been used extensively in studies on humic substances. A variety of bands characteristic of molecular structures and functional groups have been identified for these substances. The development of an attachment mounted onto FTIR spectrophotometers has allowed the determination of diffuse reflectance Fourier-transformed infrared (DRIFT) spectra. The purpose of this work was to study the applicability of DRIFT to soil organic-matter research and to compare the use of this instrumentation to dispersive and Fourier-transformed transmission IR spectroscopy. The DRIFT spectra were determined for humic acids, peat samples, and composts. In addition, the possibility of using DRIFT spectra to quantitatively measure sample concentration and measuring the relative concentration of functional groups was assessed. Sample preparation for DRIFT is much simpler than for transmission IR spectroscopy, interferences due to water adsorption are reduced, and resolution is improved. The spectra obtained using DRIFT had a higher degree of resolution as compared with dispersive and Fourier-transform transmission IR spectroscopy. Bands indicative of aliphatic C-H, carboxyl and corboxylate functional groups, aromatic C=C, and C-O stretch of polysaccharides were prominent and very well resolved. The DRIFT spectra obtained can also he used to fingerprint organic matter acquired from various sources. Spectra obtained at various concentrations of humic acid indicated that DRIFT cannot be used to estimate concentrations of organic matter in a given mixture. Relative concentrations of functional groups, however, were found to be fairly constant regardless of sample concentration. Therefore, changes in the relative concentration of functional groups can he measured during the humification process. It is expected that the application of DRIFT to organic-matter research will prove especially useful for characterizing bulky heterogeneous samples such as peat and composts.

Abstract: 1 Introduction.- 2 Principles.- 2.1 The Bouguer-Lambert-Beer Law and Its Practical Application.- 2.2 Primary Photophysical Processes.- 2.3 Vibrational Structure of Electronic Spectra.- 2.4 Electronic Spectra and Molecular Structure.- References.- 3 Photometers and Spectrophotometers.- 3.1 Photometers.- 3.2 Spectrophotometers.- 3.3 The Stray Light Error.- 3.3.1 General Observations.- 3.3.2 The Stray Light Error of Transmission and Absorbance and Its Measurement.- 3.4 Light Sources for UV-VIS Spectroscopy.- References.- 4 Analytical Applications of UV-VIS Spectroscopy.- 4.1 Photometric Determination of a Single Substance.- 4.1.1 Photometric Determination of Elements by Means of Complexing Agents.- 4.1.2 Photometric Determination of Anions and Ammonia.- 4.1.3 Photometric Water Analyses.- 4.1.4 Photometric Determination of Organic Compounds.- 4.1.5 Enzymatic Analysis and Enzyme Kinetics.- 4.2 Multicomponent Analysis.- 4.2.1 Basic Equations.- 4.2.2 An Example of a Multicomponent Analysis.- 4.3 Identification and Structure Determination.- 4.4 Chemometrics.- References.- 5 Recent Developments in UV-VIS Spectroscopy.- 5.1 Dual-Wavelength Spectroscopy.- 5.2 Derivative Spectroscopy.- 5.3 Reflectance Spectroscopy.- 5.4 Photoacoustic Spectroscopy.- 5.4.1 Principles of PAS.- 5.4.2 PAS Applications.- 5.5 Luminescence-Excitation Spectroscopy.- References.- 6 Investigation of Equilibria.- 6.1 General.- 6.2 Protolytic Equilibria pK-Values.- 6.3 Complex-Forming Equilibria.- 6.3.1 H-Bond Association.- 6.3.2 EDA Complexes.- 6.3.3 Metal Complexes.- References.- 7 Investigation of the Kinetics of Chemical Reactions.- 7.1 Fundamental Equations of Kinetics.- 7.1.1 Introduction of Absorbance as a Measurement Parameter.- 7.1.2 Classification of Other Types of Reaction.- 7.1.2.1 2nd Order Reactions.- 7.1.2.2 3rd Order Reactions.- 7.1.2.3 Pseudo 1st Order Reactions.- 7.1.2.4 Consecutive Reactions.- 7.1.2.5 Parallel Reactions.- 7.2 The Number of Linearly Independent Partial Reactions.- 7.3 Evaluation of Kinetic Measurements.- 7.4 Examples.- 7.5 Fast Reactions.- 7.5.1 Flow Methods: The Stopped-Flow Technique.- 7.5.2 Spectroscopic Relaxation Techniques.- 7.6 Photoreactions.- 7.7 Spectrometers for Kinetic Measurements.- 7.7.1 Rapid Spectrometers.- 7.7.2 FT-UV Spectrometers.- 7.7.3 Diode Array Spectrometers.- 7.8 Determination of the Spectra of Intermediates.- References.- 8 Evaluation of UV-VIS Spectral Bands.- 8.1 Oscillator Strength and Transition Moment.- 8.2 Band Analysis.- 8.2.1 Gaussian and Lorentzian Functions.- 8.2.2 Application of Derivative Spectra.- 8.3 Vibrational Structure.- References.- Index of Illustrated Absorption Spectra.

Abstract: Spatial heterodyne spectroscopy (SHS) is a new instrumental technique for interference spectroscopy which promises to extend into the FUV (1200-2000 A) spectral region the large throughput advantage at high spectral resolution usually associated with Fabry-Perot and Michelson interferometers In addition, SHS systems are compact in size, can be field-widened to increase their throughput even further, have no moving parts, and can be built in all-reflection configurations SHS appears to be well suited for high resolution, space-based spectroscopy of faint interstellar emission lines in the ultraviolet This has significant implications for the study of the dynamics and distribution of hot gas within the Galactic disk and halo For example, a field-widened SHS incorporating 5 x 5 cm gratings could obtain a radial velocity resolved (20 km/s), 3 deg angular resolution map of the high-latitude interstellar C IV 1550 emission in less than 1 year

Abstract: 1. Structural Chemistry 2. The Potential Energy Surface and the Meaning of Internuclear Distances 3. Reliability of Structure Determinations by Microwave Spectroscopy 4. Determination of Accurate Molecular Structure by Vibration-Rotation Spectroscopy 5. Gas-phase Electron Diffraction 6. X-ray Crystallography: An Introduction 7. Measurement of Accurate Bragg Intensities 8. Diffraction Studies of Molecular Motion in Crystals 9. Lattice-dynamical Interpretation of Crystallographic Thermal Parameters 10. The Role of Electron Density in X-ray Crystallography 11. Accurate Crystal Structure Analysis by Neuron Diffraction 12. Nuclear Magnetic Resonance Spectroscopy and Precise Molecular Geometries 13. Quantum Mechanical Determination of Static and Dynamic Structure 14. Molecular Mechanics 15. Crystallographic Databases: Retrieval and Analysis of Precise Structural Information From the Cambridge Structural Database 16. The Importance of Accurate Structure Determination in Organic Chemistry 17. Structure Correlations, Reaction Pathways and Energy Surfaces for Chemical Reactions 18. Structural Substituent Effects in Benzene Derivatives 19. Effect of Crystal Environment on Molecular Structures 20. The Importance of Accurate Structure Determination in Inorganic Chemistry 21. Structural variability in metal cluster compounds

Abstract: Some of the aspects of submillimeter-wave astronomy which are relevant to the field of heterodyne spectroscopy are reviewed. Most of the discussion concerns the dense interstellar medium where stars are forming, with some work presented on nearby galaxies. Extremely sensitive receivers, large accurate telescopes, and high-mountain, airborne, or space platforms are gradually being developed, so that information is steadily improving in quality and scope. Examples are given of line surveys of heavy molecule spectra, extending from millimeter wavelengths well into the submillimeter, of light molecule spectroscopy, and of atomic fine-structure spectroscopy. The importance of the spatial information on atomic and ionized carbon is discussed. The gas cooling process which allows clouds to collapse to form stars by means of the submillimeter line emission is discussed. Also covered are regions suffering shocks, photodissociation regions, and stellar outflow regions. Work on the submillimeter spectrum of nearby galaxies is briefly described. >

Abstract: Arrays of field-effect-confined quantum dots with diameters smaller than 100 nm have been prepared starting from Al x Ga 1-x As-GaAs heterostructures. In far-infrared spectroscopy, we induce transitions between the 2-meV-separated quantum levels. We observe discrete steps in the gate-voltage dependence of the integrated absorption strength indicating directly the incremental occupation of each dot with N=1, 2, 3, and 4 electrons. From the gate-voltage dependence, we can estimate a Coulomb charging energy of about 15 meV

Abstract: We examine intramolecular proton transfer in 2-(2′-hydroxyphenyl)benzoxazole in its electronic S 1 state. The experimental methods are fluorescence spectroscopy of the compound isolated in an argon matrix at 11 K and in a supersonically cooled jet, as well as femtosecond pump-and-probe spectroscopy in cyclohexane at 298 K. From the spectroscopic measurements we conclude that the vibronic bands near the electronic origin have a homogeneous width ⩾ 150 cm −1 , corresponding to a vibronic lifetime of less than 35 fs. Residual structure reveals a short progression in a vibrational mode of 147 cm −1 . The time-resolved measurements indicate a short-lived initial Franck-Condon distribution which evolves, with a time constant of 60±30 fs, into a distribution of vibrational levels which partly belong to the excited keto form of the molecule. The molecular geometries of the excited enol and keto forms are calculated using MNDO methods. For these geometries, the positions of the mobile hydrogen atom are separated by 0.41 A. We construct a model potential for excited-state intramolecular proton transfer which is consistent with the observations.

Abstract: The XUV spectra of free metal atoms obtained by absorption, photoion, photoelectron and two-photon spectroscopy are reviewed. The experimental results are discussed in comparison with the predictions of the different theoretical approaches. Emphasis is put on the basic excitation and de-excitation processes, the importance of electron correlation, on common features of groups and on trends along series.

Abstract: A brief account of the most important experimental and theoretical methods employed in surface physics is given. The use of optical spectroscopy in the study of clean semiconductor surfaces is described in detail.

Abstract: A newly developed terahertz time-domain spectrometer based on photoconductive dipole antennas driven by femtosecond laser pulses was used to measure the absorption and index of refraction for benzene, carbon tetrachloride, and cyclohexane in the far infrared. The spectra cover the region of 3-66 cm/sup -1/, where the dielectric response of the nonpolar liquids is dominated by collision induced dipole moments. With terahertz time-domain spectroscopy, information on both the real and imaginary part of the frequency response is obtained in a range difficult to access by standard techniques. >

Abstract: We report on micro‐Raman spectroscopy studies of porous silicon which show an amorphous silicon Raman line at 480 R cm−1 from regions that emit visible photoluminescence. A Raman line corresponding to microcrystalline silicon at 510 R cm−1 is also observed. X‐ray photoelectron spectroscopy data is presented which shows a high silicon‐dioxide content in porous silicon consistent with an amorphous silicon phase.

Abstract: The electron affinity of atomic iodine has been determined to be 3.059 038(10) eV. A beam of negatively charged iodine ions was merged collinearly with a laser beam. The onset of the photodetachment process was observed when the wavelength of the laser was scanned, and the result was fitted according to the Wigner law in order to determine the photodetachment threshold. The wavelength was calibrated by simultaneously recording the atomic spectra of lead and manganese as well as the fringes from a Fabry-Perot reference etalon.

Abstract: The kinematic and photometric structure of the two components of the E7/S0 galaxy NGC 4550 are evaluated quantitatively to determine the system's morphology. Attention is given to whether the data indicate a rotating bulge with a counterrotating disk or a pair of counterstreaming disks, and formation scenarios are discussed in the light of the findings. The data examined include long-slit spectroscopy with evidence of bimodality in the line-of-sight velocity distribution. Two photometrically inseparable counterstreaming disk components are identified and their velocities given. The structure and the formation scenarios given point to the feasibility of absorption of external material by galaxy disks without extreme heating. The possibility of detecting stellar counterrotation in S0 disks is discussed based on the study of NGC 4550.

Abstract: Thermally generated defects in ultrathin MgO films on Mo(100) have been investigated using high-resolution electron-energy-loss spectroscopy (HREELS) in the 0--9-eV spectral region. The results indicate that the MgO films are thermally stable and nearly free from defects up to a temperature of 1100 K, above which defects in MgO are generated. The three distinct loss features observed at 1.15, 3.58, and 5.33 eV are due to electronic transitions associated with surface F centers, F aggregates, and F (or F{sup +}) centers, respectively. The addition of lithium into the MgO films produces (Li{sup +}O{sup {minus}}) centers and promotes the production of F-type defects upon high-temperature treatment. The formation of the (Li{sup +}O{sup +}) centers is likely a consequence of the substitution of Li{sup +} for Mg{sup 2+} in the magnesium oxide lattice. The present studies have demonstrated the capabilities of HREELS for studies of electronic transitions associated with a variety of defects in the near surface region.

Abstract: Eight (Z)-isomers of lycopene were prepared by stereocontrolled syntheses and fully characterized by 1H-NMR, 13C-NMR, mass, and UV/VIS spectroscopy: (5Z)-, (7Z)-, (15Z)-, (5Z,5′Z)-, (7Z,7′Z)-, (7Z,9Z)-, (9Z,9′Z)-, and (7Z,9Z,7′Z,9′Z)-lycopene. Six additional (Z)-isomers, namely (9Z)-, (13Z)-, (5Z,9′Z)-, (9Z,13′Z)-, (5Z,9Z,5′Z)-, and (5Z,13Z,5′Z)-lycopene, were isolated in small quantities from isomer mixtures by semiprep. HPLC and were identified by 1H-NMR spectroscopy.

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Abstract: Mg+–H2O ion–molecule complexes are produced in a pulsed supersonic nozzle cluster source. These complexes are mass selected and studied with laser photodissociation spectroscopy in a reflectron time‐of‐flight mass spectrometer system. An electronic transition assigned as 2B2←X 2A1 is observed with an origin at 28 396 cm−1. The spectrum has a prominent progression in the metal‐H2O stretching mode with a frequency (ω’e) of 518.0 cm−1. An extrapolation of this progression fixes the excited state dissociation energy (D’0) at 15 787 cm−1. The corresponding ground state value (D‘0) is 8514 cm−1 (24.3 kcal/mol). The solvated bending mode, and symmetric and asymmetric stretching modes of water are also active in the complex, as are the magnesium bending modes. A second electronic transition assigned as 2B1←X 2A1 is observed with an origin at 30 267 cm−1 and a metal stretch frequency for Mg+–H2O of 488.5 cm−1 (ΔG1/2). Spectra of both excited states are also observed for Mg+–D2O. Partially resolved rotational struc...

Abstract: LiCoO2 can be viewed as the end member of the Li-doped LixCo1-xO2 system It was suggested that this system exhibits a transition from high-spin Co ions in CoO to low-spin Co ions in LiCoO2 We present a systematic study of the electronic properties of LiCoO2 based on a density-functional calculation From a good agreement between the theoretical results and the results of various spectroscopies (x-ray photoemission spectroscopy, bremsstrahlung isochromat spectroscopy, and x-ray absorption spectroscopy) we conclude that a one-particle band-structure approach is basically adequate for LiCoO2 while being still controversial for CoO) and we support the conclusion of low-spin Co ions in this compound

Abstract: The two-photon excitation spectrum in polycrystalline α-sexithienyl (T 6 ) thin films has been investigated at 4.2 K in the spectral range between 910 and 1180 nm of the fundamental laser radiation. The intense two-photon absorption band at 18 350 cm -1 is assigned to the 2 1 A g exciton band origin. The comparison of the one-photon and two-photon excitation spectra shows that the lowest "gerade" exciton level lies at 898 cm -1 above the lowest one-photon-allowed 1 2 B u exciton level.