Showing papers on "Spectroscopy published in 1999"
TL;DR: In this article, the detection of molecular vibrations in single hemoglobin (Hb) protein molecules attached to isolated and immobilized silver nanoparticles by surface enhanced Raman scattering (SERS) was demonstrated.
Abstract: We demonstrate the detection of molecular vibrations in single hemoglobin (Hb) protein molecules attached to isolated and immobilized silver nanoparticles by surface enhanced Raman scattering (SERS). A comparison between calculation and experiment indicates that electromagnetic field effects dominate the surface enhancement, and that single molecule Hb SERS is possible only for molecules situated between Ag particles. The vibrational spectra exhibit temporal fluctuations of unknown origin which appear to be characteristic of the single molecule detection limit.
2,422 citations
TL;DR: The spontaneous Raman effect, in the following simply called Raman scattering, is focused on, which can be applied noninvasively under ambient conditions in almost every environment and has special importance for ultrasensitive Raman spectroscopy at the singlemolecule level.
Abstract: In the Raman effect, incident light is inelastically scattered from a sample and shifted in frequency by the energy of its characteristic molecular vibrations. Since its discovery in 1927, the effect has attracted attention from a basic research point of view as well as a powerful spectroscopic technique with many practical applications. The advent of laser light sources with monochromatic photons at high flux densities was a milestone in the history of Raman spectroscopy and resulted in dramatically improved scattering signals (for a general overview of modern Raman spectroscopy, see refs 1-5). In addition to this so-called spontaneous or incoherent Raman scattering, the development of lasers also opened the field of stimulated or coherent Raman spectroscopies, in which molecular vibrations are coherently excited. Whereas the intensity of spontaneous Raman scattering depends linearly on the number of probed molecules, the coherent Raman signal is proportional to the square of this number (for an overview, see refs 6 and 7). Coherent Raman techniques can provide interesting new opportunities such as vibrational imaging of biological samples,8 but they have not yet advanced the field of ultrasensitive trace detection. Therefore, in the following article, we shall focus on the spontaneous Raman effect, in the following simply called Raman scattering. Today, laser photons over a wide range of frequencies from the near-ultraviolet to the near-infrared region are used in Raman scattering studies, allowing selection of optimum excitation conditions for each sample. By choosing wavelengths which excite appropriate electronic transitions, resonance Raman studies of selected components of a sample or parts of a molecule can be performed.9 In the past few years, the range of excitation wavelengths has been extended to the near-infrared (NIR) region, in which background fluorescence is reduced and photoinduced degradation from the sample is diminished. High-intensity NIR diode lasers are easily available, making this region attractive for compact, low cost Raman instrumentation. Further, the development of low noise, high quantum efficiency multichannel detectors (chargecoupled device (CCD) arrays), combined with highthroughput single-stage spectrographs used in combination with holographic laser rejection filters, has led to high-sensitivity Raman spectrometers (for an overview on state-of-the-art NIR Raman systems, see ref 10). As we shall show in section 2, the nearinfrared region also has special importance for ultrasensitive Raman spectroscopy at the singlemolecule level. As with optical spectroscopy, the Raman effect can be applied noninvasively under ambient conditions in almost every environment. Measuring a Raman spectrum does not require special sample preparation techniques, in contrast with infrared absorption spectroscopy. Optical fiber probes for bringing excitation laser light to the sample and transporting scattered light to the spectrograph enable remote detection of Raman signals. Furthermore, the spatial and temporal resolution of Raman scattering are determined by the spot size and pulse length, respectively, of the excitation laser. By using a confocal microscope, Raman signals from femtoliter volumes (∼1 μm3) can by observed, enabling spatially resolved measurements in chromosomes and cells.11 Techniques such as multichannel Hadamard transform Raman microscopy12,13 or confocal scanning Fourier transform Raman microscopy14 allow generation of high-resolution Raman images of a sample. Recently, Raman spectroscopy was performed using near-field optical microscopy.15-17 Such techniques overcome the diffraction limit and allow volumes significantly smaller than the cube of the wavelength to be investigated. In the time domain, Raman spectra can be measured on the picosecond time scale, providing information on short-lived species such as excited 2957 Chem. Rev. 1999, 99, 2957−2975
2,208 citations
TL;DR: In this paper, the properties of a Bose-Einstein condensate were studied by stimulated, two-photon Bragg scattering, and the high momentum and energy resolution of this method allowed a spectroscopic measurement of the mean-field energy and of the intrinsic momentum uncertainty of the condense.
Abstract: Properties of a Bose-Einstein condensate were studied by stimulated, two-photon Bragg scattering. The high momentum and energy resolution of this method allowed a spectroscopic measurement of the mean-field energy and of the intrinsic momentum uncertainty of the condensate. The coherence length of the condensate was shown to be equal to its size. Bragg spectroscopy can be used to determine the dynamic structure factor over a wide range of energy and momentum transfers.
886 citations
TL;DR: NIRS technology makes it possible to apply critical safety thresholds with regards to cerebral tissue saturation in order to avoid dangerously low levels with the primary goal being to reduce mortality rates and cognitive deficits due to cerebral hypoxemia.
Abstract: Near infrared spectroscopy (NIRS) is an imaging technique used in both clinical and emergency medicine, as well as in research laboratories to quantify and measure the oxygenation status of human tissue non-invasively. This is done by monitoring in vivo changes of the oxygen saturation of hemoglobin molecules in the body, based on the absorbance of near-infrared light by hemoglobin. With regards to NIRS in human tissue, this chapter will primarily be concerned with discerning the oxygenation status of cerebral tissue. The importance of such a measure, especially in cerebral physiology, is that the human brain utilizes oxygen to continuously supply neurons with energy used for vital body functioning. In the absence of oxygen, as is the case during ischemic stroke or desanguination, cognitive and functional impairment resulting in death often occurs. NIRS technology makes it possible to apply critical safety thresholds with regards to cerebral tissue saturation in order to avoid dangerously low levels with the primary goal being to reduce mortality rates and cognitive deficits due to cerebral hypoxemia.
738 citations
TL;DR: The vibrational properties of poly(3,4-ethylenedioxythiophene) (PEDT) have been studied by means of UV−vis−NIR optical absorption spectroscopy and resonance Raman scattering (RRS) with two excitation lines: green (514 nm) and infrared (1064 nm) as discussed by the authors.
Abstract: The vibrational properties of poly(3,4-ethylenedioxythiophene) (PEDT) have been studied by means of UV−vis−NIR optical absorption spectroscopy and resonance Raman scattering (RRS) spectroscopy with two excitation lines: green (514 nm) and infrared (1064 nm). The two-step oxidative doping process does not induce a drastic change for the Raman bands, but the changes that occur are clearly evidenced. During doping, new bands appear, indicating a modification of the electronic structure of the polymer. Vibrational calculations were carried out using a symmetrized dynamical matrix model and the results were compared with experimental data, especially in the 1200−1600 cm-1 range, where the CαCβ and Cβ−Cβ stretching vibrations are active. It appears that PEDT seems to have an intermediate electronic structure, between the quinoid and benzoid structures.
677 citations
Book•
1 Jan 1999
TL;DR: In this article, the Ligand Field Theory and the properties of transition metal complexes are discussed. But the authors do not discuss the applications of these properties in the field of molecular biology.
Abstract: Preface. Contributors, Volume I. Contents, Volume II. Contributors, Volume II. 1. Ligand Field Theory and the Properties of Transition Metal Complexes (A. Lever & E. Solomon). 2. Electron Paramagnetic Resonance Spectroscopy (A. Bencini & D. Gatteschi). 3. Mossbauer Spectroscopy (P. Gutlich & J. Ensling). 4. Polarized Absorption Spectroscopy (M. Hitchman & M. Riley). 5. Luminescence Spectroscopy (T. Brunold & H. Gudel). 6. Laser Spectroscopy (E. Krausz & H. Riesen). 7. IR, Raman, and Resonance Raman Spectroscopy (R. Czernuszewicz & T. Spiro). 8. Photoelectron Spectra of Inorganic and Organometallic Molecules in the Gas Phase using Synchrotron Radiation (G. Bancroft & Y. Hu). 9. X-Ray Absorption Spectroscopy and EXAFS Analysis: The Multiple-Scattering Method and Applications in Inorganic and Bioinorganic Chemistry (H. Zhang, et al.). 10. Electronic Structure Calculations on Transition Metal Complexes: Ab-Initio and Approximate Models (C. Martin & M. Zerner). 11. Electronic Structure Calculations: Density Functional Methods with Applications to Transition Metal Complexes (J. Noodleman & D. Case). Index.
657 citations
TL;DR: In this paper, carbon nitride films, deposited by reactive dc magnetron sputtering in Ar/N2 discharges, were studied with respect to composition, structure, and mechanical properties.
Abstract: Carbon nitride films, deposited by reactive dc magnetron sputtering in Ar/N2 discharges, were studied with respect to composition, structure, and mechanical properties. CNx films, with 0
475 citations
TL;DR: The present review describes the applications of IR spectroscopy to the study of membrane proteins, with an emphasis on recent work and on spectra recorded in the transmission mode, rather than using reflectance techniques.
Abstract: Infrared (IR) spectroscopy is a useful technique in the study of protein conformation and dynamics. The possibilities of the technique become apparent specially when applied to large proteins in turbid suspensions, as is often the case with membrane proteins. The present review describes the applications of IR spectroscopy to the study of membrane proteins, with an emphasis on recent work and on spectra recorded in the transmission mode, rather than using reflectance techniques. Data treatment procedures are discussed, including band analysis and diAerence spectroscopy methods. A technique for the analysis of protein secondary and tertiary structures that combines band analysis by curve-fitting of original spectra with protein thermal denaturation is described in detail. The assignment of IR protein bands in H2O and in D2O, one of the more diAcult points in protein IR spectroscopy, is also reviewed, including some cases of unclear assignments such as loops, b-hairpins, or 310-helices. The review includes monographic studies of some membrane proteins whose structure and function have been analysed in detail by IR spectroscopy. Special emphasis has been made on the role of subunit III in cytochrome c oxidase structure, and the proton pathways across this molecule, on the topology and functional cycle of sarcoplasmic reticulum Ca 2+ -ATPase, and on the role of lipids in determining the structure of the nicotinic acetylcholine receptor. In addition, shorter descriptions of retinal proteins and references to other membrane proteins that have been studied less extensively are also included. # 1999 Elsevier Science Ltd. All rights reserved.
433 citations
TL;DR: It is shown that the commonly used 2pK models are incapable to incorporate in the adsorption modeling the correct bidentate binding mechanism found by spectroscopy, and the CD-MUSIC model can successfully describe the macroscopic Adsorption phenomena using the surface speciation and binding mechanisms as found bySpectroscopy.
403 citations
TL;DR: In this paper, a large increase in atomic absorption due to coherent interaction with resonant radiation is predicted for a closed transition between two degenerate atomic levels verifying the total angular momentum of the ground and the excited levels, respectively.
Abstract: A large increase in atomic absorption due to coherent interaction with resonant radiation is predicted for a closed transition between two degenerate atomic levels verifying $0l{F}_{g}l{F}_{e}{(F}_{g}$ and ${F}_{e}$ are the total angular momentum of the ground and the excited levels, respectively). In good agreement with the theoretical prediction, a total absorption enhancement by a factor 1.7 was obtained on the ${D}_{2}$ line of ${}^{85}\mathrm{Rb}\mathrm{}$ in a vapor cell experiment.
396 citations
TL;DR: In this article, local spectra of self-affine clusters of silver colloid particles recorded with subwavelength resolution by near-field spectroscopy are reported, which consist of several resonances with highly location-dependent frequencies.
Abstract: Local spectra of self-affine clusters of silver colloid particles recorded with subwavelength resolution by near-field spectroscopy are reported. Spectra were also simulated computationally. The observed and calculated near-field spectra consist of several resonances with highly location-dependent frequencies. The most highly resolved of these resonances correspond to individual surface plasmon (SP) normal modes. All of these features are only observable in the near field. Both theory and experiment also show that when excited by light in the SP region of the spectrum, the field-intensity distribution in the near field is very heterogeneous with most of the excitation concentrated in ``hot spots'' on the cluster surface that are strongly excitation-wavelength dependent. This field-intensity localization provides a rationale for recently reported surface-enhanced Raman enhancements in excess of ${10}^{10}.$
TL;DR: In this article, a review of recent results in the spectroscopy of single CdSe nanocrystal quantum dots is presented, including ultra-narrow emission lineshapes (∼600× narrower than ensemble spectra), a highly polarizable emitting state in the presence of strong local electric fields, line broadening as a result of environmental fluctuations, and shifting of the emission spectra over a wide range of energies.
Abstract: We review some recent results in the spectroscopy of single CdSe nanocrystal quantum dots. By eliminating the effects of inhomogeneous broadening and ensemble averaging, single nanocrystal spectroscopy has revealed many new and previously unexpected physical phenomena. Among those discussed in this review are ultra-narrow emission lineshapes (∼600× narrower than ensemble spectra), a highly polarizable emitting state in the presence of strong local electric fields, line broadening as a result of environmental fluctuations, and shifting of the emission spectra over a wide range of energies (from less than 300 μeV to 80 meV). In addition, polarization spectroscopy of single nanocrystals has revealed the presence of a theoretically predicted two-dimensional transition dipole moment oriented in the xy plane of the nanocrystals. As a result, it is, in principle, possible to use polarization spectroscopy to determine the three-dimensional orientation of individual nanocrystals. These and other studies of single quantum dots have provided us with significant insight into the detailed physics and dynamics of this unique and fascinating physical system.
Book•
14 May 1999
TL;DR: In this paper, a summary of molecular structure and molecular spectra is presented, including the width and shape of Spectral Lines and Radiative Transfer and Population Distributions in elementary plasma spectroscopy.
Abstract: Introduction.- Basic Atomic Theory.- Atomic Structure and Atomic Spectra.- The Analysis of Atomic Spectra.- A Summary of Molecular Structure.- Molecular Spectra.- Emission and Absorbtion.- The Width and Shape of Spectral Lines.- Radiative Transfer and Population Distributions.- Elementary Plasma Spectroscopy.- Introduction to Experimental Methods.- Dispersive Spectrometers.- Interferometric Spectrometers.- Laser Spectroscopy.- Light Sources and Detectors.- Experimental Determination of Transition Probabilities and Radiative Lifetimes.
Book•
1 Jan 1999
TL;DR: The non-coplanar symmetric (e, 2e) reaction at several kilovolts is understood so well that it provides an accurate and sensitive tool for observing the motion and correlation of electrons in atoms and molecules as discussed by the authors.
Abstract: The non-coplanar symmetric (e, 2e) reaction at several kilovolts is understood so well that it provides an accurate and sensitive tool for observing the motion and correlation of electrons in atoms and molecules. Examples are given of both the determination of experimentally defined orbitals; which are equivalent within experimental error to orbitals calculated by appropriate variational methods, and of quantities dependent on initial- and final-state correlations.
TL;DR: The spontaneous Raman effect has attracted attention from a basic research point of view as well as a powerful spectroscopic technique with many practical applications as discussed by the authors, however, it has not yet advanced the field of ultrasensitive trace detection.
Abstract: In the Raman effect, incident light is inelastically scattered from a sample and shifted in frequency by the energy of its characteristic molecular vibrations. Since its discovery in 1927, the effect has attracted attention from a basic research point of view as well as a powerful spectroscopic technique with many practical applications. The advent of laser light sources with monochromatic photons at high flux densities was a milestone in the history of Raman spectroscopy and resulted in dramatically improved scattering signals (for a general overview of modern Raman spectroscopy, see refs 1-5). In addition to this so-called spontaneous or incoherent Raman scattering, the development of lasers also opened the field of stimulated or coherent Raman spectroscopies, in which molecular vibrations are coherently excited. Whereas the intensity of spontaneous Raman scattering depends linearly on the number of probed molecules, the coherent Raman signal is proportional to the square of this number (for an overview, see refs 6 and 7). Coherent Raman techniques can provide interesting new opportunities such as vibrational imaging of biological samples,8 but they have not yet advanced the field of ultrasensitive trace detection. Therefore, in the following article, we shall focus on the spontaneous Raman effect, in the following simply called Raman scattering. Today, laser photons over a wide range of frequencies from the near-ultraviolet to the near-infrared region are used in Raman scattering studies, allowing selection of optimum excitation conditions for each sample. By choosing wavelengths which excite appropriate electronic transitions, resonance Raman studies of selected components of a sample or parts of a molecule can be performed.9 In the past few years, the range of excitation wavelengths has been extended to the near-infrared (NIR) region, in which background fluorescence is reduced and photoinduced degradation from the sample is diminished. High-intensity NIR diode lasers are easily available, making this region attractive for compact, low cost Raman instrumentation. Further, the development of low noise, high quantum efficiency multichannel detectors (chargecoupled device (CCD) arrays), combined with highthroughput single-stage spectrographs used in combination with holographic laser rejection filters, has led to high-sensitivity Raman spectrometers (for an overview on state-of-the-art NIR Raman systems, see ref 10). As we shall show in section 2, the nearinfrared region also has special importance for ultrasensitive Raman spectroscopy at the singlemolecule level. As with optical spectroscopy, the Raman effect can be applied noninvasively under ambient conditions in almost every environment. Measuring a Raman spectrum does not require special sample preparation techniques, in contrast with infrared absorption spectroscopy. Optical fiber probes for bringing excitation laser light to the sample and transporting scattered light to the spectrograph enable remote detection of Raman signals. Furthermore, the spatial and temporal resolution of Raman scattering are determined by the spot size and pulse length, respectively, of the excitation laser. By using a confocal microscope, Raman signals from femtoliter volumes (∼1 μm3) can by observed, enabling spatially resolved measurements in chromosomes and cells.11 Techniques such as multichannel Hadamard transform Raman microscopy12,13 or confocal scanning Fourier transform Raman microscopy14 allow generation of high-resolution Raman images of a sample. Recently, Raman spectroscopy was performed using near-field optical microscopy.15-17 Such techniques overcome the diffraction limit and allow volumes significantly smaller than the cube of the wavelength to be investigated. In the time domain, Raman spectra can be measured on the picosecond time scale, providing information on short-lived species such as excited 2957 Chem. Rev. 1999, 99, 2957−2975
TL;DR: In this article, the aluminum incorporation in tetrahedral−octahedral−tetra... was characterized using 27Al magic angle spinning nuclear magnetic resonance spectroscopy at different magnetic fields.
Abstract: 27Al magic angle spinning nuclear magnetic resonance (27Al MAS NMR) spectroscopy at different magnetic fields was used to characterize the aluminum incorporation in the tetrahedral−octahedral−tetra...
TL;DR: In this paper, an innovative approach has been used to probe the molecular nature of the metal oxide/aqueous solution interface using internal reflection spectroscopy of thin colloidal TiO2 films, under aqueous solutions of pH 11.7−2.3.
Abstract: An innovative approach has been used to probe the molecular nature of the metal oxide/aqueous solution interface. Internal reflection spectroscopy of thin colloidal TiO2 films, under aqueous solutions of pH 11.7−2.3, has been used to obtain differential in situ infrared spectra related to interfacial species. An alkaline solution wash of the TiO2 films was shown to remove contaminants arising from the sol evaporation−film deposition process. Specific infrared absorptions have been assigned to terminal Ti−OH and Ti−OH2+, adsorbed water Ti−OH2, and bridging Ti−OH+−Ti species from the pH dependence of spectra and from deuteration experiments. These surface species determine the pH-dependent surface charge and the enhanced interfacial ionic concentrations observed in our previously published STIRS results. The enhanced interfacial ionic concentrations were also observed to have spectral effects related to interfacial water structure which are similar to those observed from concentrated aqueous solutions conta...
TL;DR: In this paper, pure and Pb-doped (5 and 10mol %) titanium dioxide (TiO2) thin films have been deposited on single-crystal Si (100) and vitreous silica substrates by the sol-gel dip-coating method.
TL;DR: In this paper, a combination of IR absorption spectroscopy and mass spectrometry has been applied to dusty radiofrequency (RF) plasmas in methane, acetylene and ethylene.
Abstract: Infrared (IR) absorption spectroscopy and mass spectrometry have been simultaneously applied to dusty radiofrequency (RF) plasmas in methane, acetylene and ethylene. The combination of IR absorption spectroscopy and mass spectrometry allows the chemical composition and structure of the most relevant plasma-produced neutral species, the ionic plasma composition and the chemical composition of the nanometer-sized particles to be precisely identified. The production of acetylenic compounds (C2Hx) seems to be a key mechanism for the powder formation in all the investigated hydrocarbon plasmas. Electron attachment to acetylenic compounds and the following ion-neutral reactions might lead to the high-mass carbon anions, which are trapped in the plasma and finally end in powder formation. The hydrogenation of the monomer strongly influences the composition of the ions. Finally the composition of the plasma-produced particles is mainly sp3 bonded carbon and the infrared spectra show similarities to that of polyethylene.
TL;DR: A number of unsymmetrical Pc's and Nc's have been synthesized in moderate yields by the ring expansion reaction of structurally distorted subphyrin derivatives with isoindolediimine derivatives in dimethyl sulfoxide−chloronaphthalene (or chlorobenzenes or aromatic hydrocarbons such as toluene and xylene) mixtures as mentioned in this paper.
Abstract: A subazaporphyrin (SubAP), tert-butylated and crowned subphthalocyanines (tBSubPc and SubCRPc), a μ-oxo dimer of tert-butylated SubPc {(tBSubPc)2O}, a subnaphthalocyanine (SubNc), and monosubstituted type unsymmetrical phthalocyanine (Pc) and naphthalocyanine (Nc) analogues have been synthesized. In particular, unsymmetrical Pc's and Nc's have been prepared in moderate yields by the ring expansion reaction of structurally distorted SubPc's and SubNc's with isoindolediimine derivatives in dimethyl sulfoxide−chloronaphthalene (or chlorobenzenes or aromatic hydrocarbons such as toluene and xylene) mixtures. The compounds have been characterized by electronic absorption, magnetic circular dichroism (MCD), fluorescence emission, and nuclear magnetic resonance spectroscopy. Both the Soret bands and Q-bands shift to longer wavelength and gain intensity in the order SubAP, SubPc, and SubNc. Fluorescence quantum yields and lifetimes generally decrease with decreasing molecular symmetry. Circular dichroism and NMR ...
TL;DR: In this paper, the correlation between internal structure and spectral behavior of carbon black is investigated experimentally by using high-resolution transmission electron microscopy, electron energy loss spectroscopy, 13 C NMR spectrograms, and Raman spectrographs.
Abstract: The internal structure of carbon black particles considerably influences the optical behavior of the material, apart from the shape and agglomeration state of the primary particles. In this paper the correlation between internal structure and spectral behavior of carbon black is investigated experimentally. The carbon blacks were produced by resistive heating of graphite electrodes and condensation in a cooling gas atmosphere. The internal structure of the primary carbon black particles was investigated by high-resolution transmission electron microscopy, electron energy loss spectroscopy, 13 C NMR spectroscopy, and Raman spectroscopy. The primary particles were found to consist of bent or plane structural subunits. The UV π−π* absorption feature of the produced carbon blacks varies in position between 196 and 265 nm depending on the state of bending of the graphene layers in the subunits of particles and/or the dimensions of the plane graphitic microcrystallites and the incorporation of hydrogen. The different curvature radii of the graphene layers or the sizes of microcrystallites can be summarized by an integral dimension like the ratio of sp2/sp3 hybridized carbon atoms. In the mid-infrared spectral region, the absolute value of the absorption coefficient κ is dominated by a continuous absorption due to free charge carriers which are also influenced by the ratio of sp2/sp3 hybridized carbon in the primary particles. The appearance of prominent bands is related to the existence of functional groups, like C–Hn, CO and/or C–O–C.
TL;DR: In this paper, the photodissociation and photoionization of liquid water following two-photon absorption at 266 nm was studied in the spectral range from 213 to 1108 nm with sub-picosecond time resolution.
Abstract: The photodissociation and photoionization of liquid water following two-photon absorption at 266 nm is studied in the spectral range from 213 to 1108 nm with subpicosecond time resolution. Probing in the UV enables the first direct simultaneous observation of the photoproducts eaq−, Haq, and OHaq. This makes it possible to follow the geminate recombination kinetics between the photoproducts and to determine the relative yields of the dissociation and ionization channels. The concentration of hydrated electrons deduced from the visible and near-infrared transient absorption measurements decays by 40%±2% within the first 90 ps due to recombination with OHaq and H3O+. Analyzing our measurements of the hydrated electron concentration using the independent reaction time approximation results in the relative yields of 82%±3% and 18%±3% for recombination with OHaq and with H3O+, respectively. This is in excellent agreement with the relative yield of 82%±10% for recombination with OHaq determined directly from ou...
TL;DR: In this article, an experimental investigation of the far-infrared properties of several nonlinear crystals using terahertz time-domain spectroscopy (THz-TDS) was reported.
Abstract: In this article we report an experimental investigation of the far-infrared properties of several nonlinear crystals, LiNbO3, LiTaO3, ZnTe and CdTe Using Terahertz Time-Domain Spectroscopy (THz-TDS) we have measured the complex frequency response, ie both index of refraction and absorption up to 3 THz (100 cm−1) for the electro-optic crystals at room temperature The single Lorentzian oscillator model is used to describe the aquired data Additional resonance features are observed, especially in the II-VI compounds
TL;DR: In this paper, the AC Stark shift of atomic levels in an external, subatomic strength variable field is considered and theoretical predictions concerning the disturbance of atomic spectra by fields of atomic and superatomic strength are discussed.
Abstract: Calculated and experimental data on the AC Stark shift of atomic levels in an external, subatomic-strength variable field are considered. Theoretical predictions concerning the disturbance of atomic spectra by fields of atomic and superatomic strength are discussed. The limiting value of the atomic AC Stark shift in a light-frequency radiation field is estimated.
TL;DR: In this article, the results indicate the presence of different chemical forms of oxygen atoms (two types of O2-, OH-, organic oxygens and H2O) which evolve with surface treatment.
1 Oct 1999
TL;DR: The PIMA-II as mentioned in this paper is a portable short-wave infrared (SWIR) spectrometers that provides a valuable tool for evaluating the distribution of alteration assemblages.
Abstract:
Alteration mineral assemblages are important to the understanding of and exploration for hydrothermal ore deposits. Conventional mapping tools may not identify fine-grained minerals or define important compositional variations. Field portable short-wave infrared (SWIR) spectrometers solve some of these problems and provide a valuable tool for evaluating the distribution of alteration assemblages. Spectrometers such as the PIMA-II allow rapid identification of minerals and mineral-specific variations at a field base. Mineral assemblages, integrated with other exploration data, are then used to target drill holes and guide regional exploration programs. Data collection must be systematically organized and carried out by a trained operator. Analysis of data sets requires the use of spectral reference libraries from different geological environments and may be aided in some cases by computer data processing packages. Integration of results with field observations, petrography, and X-ray diffraction analysis is necessary for complete evaluation. The PIMA (portable infrared mineral analyzer) has been used successfully in the high-sulfidation epithermal, low-sulfidation epithermal, volcanogenic massive sulfide (VMS) and intrusion-related environments. Case studies from these systems demonstrate the ability to rapidly acquire and process SWIR data and produce drill logs and maps. The resulting information is critical for targeting.
TL;DR: In this paper, the authors compare ISO classifications -starburst or active galactic nucleus (AGN) with classifications from optical spectroscopy, and with optical/near-infrared searches for hidden broad-line regions.
Abstract: New tools from Infrared Space Observatory (ISO) mid-infrared spectroscopy have recently become available to determine the power sources of dust-obscured ultraluminous infrared galaxies (ULIRGs). We compare ISO classifications - starburst or active galactic nucleus (AGN) - with classifications from optical spectroscopy, and with optical/near-infrared searches for hidden broad-line regions. The agreement between mid-infrared and optical classification is excellent if optical LINER spectra are assigned to the starburst group. The starburst nature of ULIRG LINERs strongly supports the suggestion that LINER spectra in infrared-selected galaxies, rather than being an expression of the AGN phenomenon, are due to shocks that are probably related to galactic superwinds. Differences between ISO and optical classification provide clues on the evolution of ULIRGs and on the configuration of obscuring dust. We find few ISO AGN with optical HII or LINER identification, suggesting that highly obscured AGN exist but are not typical for the ULIRG phenomenon in general. Rather, our results indicate that strong AGN activity, once triggered, quickly breaks the obscuring screen at least in certain directions, thus becoming detectable over a wide wavelength range.
TL;DR: In this paper, the structure of hybrid SiO2−B2O3 gels was investigated by Fourier-transformed infrared (FT-IR) spectroscopy, 29Si and 11B solid-state nuclear magnetic resonance (NMR), X-ray diffraction (XRD), and chemical analysis.
Abstract: Hybrid SiO2−B2O3 gels have been synthesized from cohydrolysis of modified silicon alkoxides (R−Si(OE)3 R = Me, Vi, Et) and triethylborate, B(OEt)3. The structure of these gels was investigated by Fourier-transformed infrared (FT-IR) spectroscopy, 29Si and 11B solid-state nuclear magnetic resonance (NMR), X-ray diffraction (XRD), and chemical analysis. The results show, for the first time, the possibility of obtaining a SiO2−B2O3 gel in which trigonal boron atoms are homogeneously dispersed in the siloxane network via B−O−Si bonds. The identification of such bonds was mainly based on the FT-IR and 11B MAS NMR results. The formation of the borosiloxane bonds is favored by increasing the pH of hydrolysis water and by the use of Et− or Vi−Si(OR)3 rather than Me−Si(OEt)3. Some hypotheses to rationalize the experimental results are also presented.
TL;DR: In this paper, the experimental conditions and procedure for quantitative analysis of steel by laser-induced breakdown spectroscopy in argon at atmospheric pressure using an infrared Nd:YAG laser have been studied.
Abstract: The experimental conditions and procedure for quantitative analysis of steel by laser-induced breakdown spectroscopy in argon at atmospheric pressure using an infrared Nd:YAG laser have been studied. Satisfactory analytical results have been obtained for the determination of C, Si, Cr, and Ni contents in low-alloyed steels. The lens-to-sample distance is shown to be a relevant parameter, which can be selected at each pulse energy to enhance the line intensities and the repeatability of measurements. A higher precision has been obtained for line-intensity ratios (0.9-2.5% relative standard deviation for concentrations higher than 0.1%) than for absolute intensity measurements. The calibration curves for all the elements have correlation coefficients above 0.999. Detection limits are in the range 6-80 ppm.