Showing papers on "Fourier transform spectroscopy published in 2012"

Fourier Transform Infrared Spectroscopy for Natural Fibres

Abstract: Infrared spectroscopy is nowadays one of the most important analytical techniques available to scientists. One of the greatest advantages of the infrared spectroscopy is that virtually any sample in any state may be analyzed. For example, liquids, solutions, pastes, powders, films, fibres, gases and surfaces can all be examined with a judicious choice of sampling technique. The review by Annette, Sudhakar, Ursula and Andrea [1-2] also demonstrates the applicability of dispersion infrared spectroscopy for natural fibres studies.

Two-dimensional Fourier transform electronic spectroscopy

Abstract: Two-dimensional Fourier transform electronic spectra of the cyanine dye IR144 in methanol are used to explore new aspects of optical 2D spectroscopy on a femtosecond timescale. The experiments reported here are pulse sequence and coherence pathway analogs of the two-dimensional magnetic resonance techniques known as COSY (correlated spectroscopy) and NOESY (nuclear Overhauser effect spectroscopy). Noncollinear three pulse scattering allows selection of electronic coherence pathways by choice of phase matching geometry, temporal pulse order, and Fourier transform variables. Signal fields and delays between excitation pulses are measured by spectral interferometry. Separate real (absorptive) and imaginary (dispersive) 2D spectra are generated by measuring the signal field at the sample exit, performing a 2D scan that equally weights rephasing and nonrephasing coherence pathways, and phasing the 2D spectra against spectrally resolved pump–probe signals. A 3D signal propagation function is used to correct the...

Adaptive dual-comb spectroscopy in the green region

Abstract: Dual-comb spectroscopy is extended to the visible spectral range with two short-pulse frequency-doubled free-running ytterbium-doped fiber lasers. When the spectrum is shifted to other domains by nonlinear frequency conversion, tracking the relative fluctuations of the femtosecond oscillators at their fundamental wavelength automatically produces the correction signal needed for the recording of distortion-free spectra. The dense rovibronic spectrum of iodine around 19,240 cm−1 is recorded within 12 ms at Doppler-limited resolution.

Comparative investigation of Fourier transform infrared (FT-IR) spectroscopy and X-ray diffraction (XRD) in the determination of cotton fiber crystallinity.

Abstract: Despite considerable efforts in developing curve-fitting protocols to evaluate the crystallinity index (CI) from X-ray diffraction (XRD) measurements, in its present state XRD can only provide a qualitative or semi-quantitative assessment of the amounts of crystalline or amorphous fraction in a sample. The greatest barrier to establishing quantitative XRD is the lack of appropriate cellulose standards, which are needed to calibrate the XRD measurements. In practice, samples with known CI are very difficult to prepare or determine. In a previous study, we reported the development of a simple algorithm for determining fiber crystallinity information from Fourier transform infrared (FT-IR) spectroscopy. Hence, in this study we not only compared the fiber crystallinity information between FT-IR and XRD measurements, by developing a simple XRD algorithm in place of a time-consuming and subjective curve-fitting process, but we also suggested a direct way of determining cotton cellulose CI by calibrating XRD with the use of CI(IR) as references.

Two-dimensional-Raman-terahertz spectroscopy of water: Theory

Abstract: We discuss the hybrid 2D-Raman-THz spectroscopy of liquid water This two-dimensional spectroscopy is designed to directly work in the low-frequency range of the intermolecular degrees of freedom The information content of 2D-Raman-THz spectroscopy is similar to 2D-Raman or 2D-THz spectroscopy, but its experimental implementation should be easier That is, 2D-Raman-THz spectroscopy is a 3rd-order nonlinear spectroscopy and as such completely avoids cascading of consecutive 3rd-order signals, which turned out to be a major difficulty in 5th-order 2D-Raman spectroscopy On the other hand, it does not require any intense THz pump-pulse, the lack of which limits 2D-THz spectroscopy to the study of semiconductor quantum wells as the currently available pulse energies are too low for molecular systems In close analogy to 2D-Raman spectroscopy, the 2D-Raman-THz response of liquid water is simulated from an all-atom molecular dynamics simulation, and the expected spectral features are discussed

Optical two-dimensional Fourier transform spectroscopy of semiconductor nanostructures [Invited]

Abstract: Optical two-dimensional Fourier transform (2DFT) spectroscopy has been developed over the last decade as a powerful tool for studying a variety of physical systems, ranging from atoms to molecules to solids. This review covers our use of 2DFT spectroscopy to study exciton dynamics in semiconductor nanostructures. In quantum wells, 2DFT spectroscopy confirms the importance of many-body contributions to the coherent optical response and reveals nonradiative double-quantum and Raman coherences. For natural quantum dots, 2DFT spectroscopy enables ensemble measurements of the homogeneous linewidth, including the temperature and density dependence. Relaxation from quantum well states into the quantum dots can also be studied using 2DFT spectroscopy.

Ultra-compact snapshot imaging fourier transform spectrometer

Abstract: Snapshot imaging Fourier transform spectrometers include a lens array that produces sub-images that are directed through a birefringent interferometer in orthogonal polarization eigenstates that acquire an optical path difference. Interference patterns based on this OPD can be Fourier transformed to obtain a spectral image. In some examples, polarizing gratings provide a spatial heterodyne frequency and offset the spectra.

Cooling molecules in a cell for FTMW spectroscopy

Abstract: Gas phase benzonitrile, acetone, 1-2 propanediol, fluorobenzene, and anisole molecules are produced in a cell at a temperature of 8 K, and detected via Fourier transform microwave spectroscopy (FTMW). Helium buffer gas is used to cool the molecules originating from a high flux room temperature beam. This general, continuous source of cold molecules offers comparable spectral resolution to existing seeded pulsed supersonic beam/FTMW spectroscopy experiments but with higher number sensitivity. It is also an attractive tool for quantitative studies of cold molecule–helium and molecule–molecule elastic and inelastic collisions. Preliminary data on helium–molecule low temperature rotational and vibrational relaxation cross-sections are presented. Applications of the technique as a sensitive broad spectrum mixture analyser and a high resolution slow-beam spectrometer are discussed.

Optical Spectroscopy: Future Fourier transform spectroscopy

Abstract: Synonyms: Bacterial lipids from Acholeplasma laidlawii and Escherichia coli; Cholesterol; Lateral phase separation; Lipid domain; Lipid membrane; Lipid packing; Lipid phase equilibria; Lipid raft; ...

Two-dimensional fourier transform spectroscopy of adenine and uracil using shaped ultrafast laser pulses in the deep UV.

Abstract: We compare two-dimensional (2D) ultrafast Fourier transform spectroscopy measurements in the deep UV (262 nm) for adenine and uracil in solution. Both molecules show excited-state absorption on short time scales and ground-state bleaching extending for over 1 ps. While the 2D spectrum for uracil shows changes in the center of gravity during the first few hundred femtoseconds, the center of gravity of the 2D spectrum for adenine does not show similar changes. We discuss our results in light of ab initio electronic structure calculations.

Optical 2-D Fourier Transform Spectroscopy of Excitons in Semiconductor Nanostructures

Abstract: Optical 2-D Fourier transform spectroscopy is a powerful technique for studying resonant light-matter interactions, determining the transition structure and monitoring dynamics of optically created excitations. The ability to separate homogeneous and inhomogeneous broadening is one important capability. In this paper, we discuss the use of this technique to study excitonic transitions in semiconductor nanostructures. In quantum wells, the effects of structural disorder is observed as inhomogeneous broadening of the exciton resonances. In quantum dots, the temperature dependence of the homogeneous width gives insight into the nature of the dephasing processes.

Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy of a single endothelial cell.

Abstract: Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) with the use of a slide-on germanium accessory followed by chemometric analysis allowed for providing meaningful information about the biochemical composition of a single endothelial cell. In this work, the methodology of the ATR-FTIR measurements of dried cells and dried cells immersed in water solution is presented. The contact of the cell and Ge crystal was set up manually and monitored through the integration of the amide I band. Additionally, the cell imaging in transreflection mode was tested, but the spectral differences between sub-cellular structures were not prominent in the registered spectra. It has been shown that the ATR-FTIR method gives better results due to the increased spatial resolution and S/R ratio as well as small contribution of the optical artifacts.

Fourier Transform Infrared (FTIR) Spectroscopy

Abstract: Infrared (IR) spectroscopy has always been a powerful tool for the identification of organic materials. However, with the development of Fourier transform infrared (FTIR) spectroscopy, it has become a more popular method for the quantitative analysis of complex mixtures, as well as the investigation of surface and interfacial phenomena. This chapter reviews the basic theory behind FTIR spectroscopy and describes the currently used instrumentation and its application to gas, liquid, bulk and powdered solid samples, and thin films using both transmission and reflectance methods, including specular, diffuse, and attenuated total reflectance (ATR) techniques. The optimization of instrumental parameters, sample handling techniques, signal processing, and data analysis are described. The characteristic vibrational absorption bands used for the identification of key chemical structures as well as methods for quantitative measurement of chemical composition are overviewed. Potential problems often encountered in using the different FTIR techniques in material and chemical species characterization and are also discussed in an effort to help the nonexpert in the field to make the best use of these powerful methods. Keywords: Fourier transform infrared spectroscopy; diffuse reflectance FTIR; attenuated total reflectance

A matter of scale: from far‐field microscopy to near‐field nanoscopy

Abstract: Vibrational spectroscopy is a powerful analytical tool which provides chemical information about a sample without a priori knowledge. By combining vibrational spectroscopy with different microscopic techniques, scientists can visualize and characterize the chemical composition of a sample on length scales which cover many orders of magnitude; from far-field radiation used in microwave astronomy and Fourier transform infrared microscopy, to near-field scattering used in tip-enhanced Raman spectroscopy and scanning near-field optical or infrared microscopy. Here, various modern chemical mapping techniques are reviewed and their advantages and disadvantages are discussed. Also, a basic theoretical background is provided for each technique along with several illustrative examples.

A Fourier transform infrared trace gas analyser for atmospheric applications

Abstract: The authors present the optimisation of a commercial FTIR spectrometer for the analysis of trace gas mixing ratios (CO2, CH4, CO, N2O) and their isotopic composition (d13C-CO2, dD-H2O, d15N-N2O). Additionally, various applications are given, ranging from clean air monitoring, mobile platforms, point source emission detection, tower profile and flux measurements to different chamber measurements.

Characterization of Phospholipid Bilayer Formation on a Thin Film of Porous SiO2 by Reflective Interferometric Fourier Transform Spectroscopy (RIFTS)

Abstract: Classical methods for characterizing supported artificial phospholipid bilayers include imaging techniques such as atomic force microscopy and fluorescence microscopy. The use in the past decade of surface-sensitive methods such as surface plasmon resonance and ellipsometry, and acoustic sensors such as the quartz crystal microbalance, coupled to the imaging methods, have expanded our understanding of the formation mechanisms of phospholipid bilayers. In the present work, reflective interferometric Fourier transform spectrocopy (RIFTS) is employed to monitor the formation of a planar phospholipid bilayer on an oxidized mesoporous Si (pSiO2) thin film. The pSiO2 substrates are prepared as thin films (3 μm thick) with pore dimensions of a few nanometers in diameter by the electrochemical etching of crystalline silicon, and they are passivated with a thin thermal oxide layer. A thin film of mica is used as a control. Interferometric optical measurements are used to quantify the behavior of the phospholipids ...

Fourier transform infrared spectroscopy approach for measurements of photoluminescence and electroluminescence in mid-infrared

Abstract: An improved Fourier transform infrared spectroscopy approach adapting to photoluminescence and electroluminescence measurements in mid-infrared has been developed, in which diode-pumped solid-state excitation lasers were adopted for photoluminescence excitation. In this approach, three different Fourier transform infrared modes of rapid scan, double modulation, and step scan were software switchable without changing the hardware or connections. The advantages and limitations of each mode were analyzed in detail. Using this approach a group of III–V and II–VI samples from near-infrared extending to mid-infrared with photoluminescence intensities in a wider range have been characterized at room temperature to demonstrate the validity and overall performances of the system. The weaker electroluminescence of quantum cascade lasers in mid-infrared band was also surveyed at different resolutions. Results show that for samples with relatively strong photoluminescence or electroluminescence out off the background, rapid scan mode is the most preferable. For weaker photoluminescence or electroluminescence overlapped with background, double modulation is the most effective mode. To get a better signal noise ratio when weaker photoluminescence or electroluminescence signal has been observed in double modulation mode, switching to step scan mode should be an advisable option despite the long data acquiring time and limited resolution.

Fourier Transform Infrared Imaging of Bone

Abstract: Fourier transform infrared imaging (FTIRI) is a technique that can be used to analyze the material properties of bone using tissue sections. This chapter describes the basic principles of FTIR and the methods for capturing and analyzing FTIR images in bone sections.

CO 2 Adsorption and Desorption on MgO/Al 2 O 3 : An In Situ Diffuse Reflection Infrared Fourier Transform Spectroscopy (DRIFTS) Study

Abstract: The adsorption and desorption of CO2 on MgO/Al2O3 were investigated by in situ diffuse reflection infrared Fourier transform spectroscopy (DRIFTS) combined with the method of curve-fitting analysis. The spectroscopic results indicate that there are three chemisorbed surface species formed on the MgO/Al2O3, i.e., free carbonate ion, bridged carbonate, and bidentate carbonate species, which correspond to the peaks at 1675, 1403, and two peaks at 1610 and 1340 cm−1, respectively, when the sample was exposed in CO2 flow at 130 °C. The quantification analysis of the spectra during CO2 adsorption and desorption shows that the formation and desorption rates of all surface species are coverage dependent. Among the three species, the bridged carbonate shows the highest speed of formation and desorption, indicating that this type of species may be beneficial to CO2 capture and release. It should also be noted that the contribution of support Al2O3 to CO2 capture is negligible. This study may help us to understand the interaction between CO2 and metal oxides and thus to give more insights into CO2 capture using solid sorbents.

Methods in physical chemistry

Abstract: VOLUME I GAS-PHASE Manipulation of molecules High resolution infrared spectroscopy Laser ionisation spectroscopy Laser spectroscopy for gas-phase kinetics Mass spectrometry for ion chemistry CONDENSED-PHASE Nuclear magnetic resonance Electron spin resonance Broadband conductivity spectroscopy X-ray absorption spectroscopy X-ray, neutron and electron diffraction Small-angle scattering with neutrons and X-rays Perturbed angular correlation Mossbauer spectroscopy VOLUME II INTERFACES Diffuse-Reflection-Infrared-FT-Spectroscopy Raman spectroscopy Photoelectron spectroscopy and microscopy Secondary ion mass spectrometry Quartz microbalance Scanning tunneling microscopy BIOMOLECULES AND MATERIALS Ultrafast vibrational spectroscopies THz spectroscopy Single molecule fluorescence spectroscopy Luminescence Nanomechanical methods Magnetometry Transient isotopic kinetic techniques High resolution electron microscopy

Polychromatic Decoupling of a Manifold of Homonuclear Scalar Interactions in Solution‐State NMR

Abstract: Keywords: Fourier transform spectroscopy ; homonuclear decoupling ; J-coupling ; NMR spectroscopy Reference EPFL-ARTICLE-181116doi:101002/chem201200481View record in Web of Science Record created on 2012-09-03, modified on 2017-05-12

Integrated Band Intensities of Ethylene (1224) by Fourier Transform Infrared Spectroscopy

Abstract: The integrated band intensities of ethylene (12C2H4) in the 640–3260 cm−1 region were determined by Fourier transform infrared (FTIR) spectroscopy. The infrared absorbance spectra of the 𝜈7 and 𝜈10, 𝜈12, 𝜈7

Fourier Transform Infrared Spectroscopy - Useful Analytical Tool for Non-Destructive Analysis

Abstract: It is highly recognized that the use of Fourier Transform Infrared Spectrometry (FTIR) for chemical substances identification it is not a trivial task to be fulfilled by analytical chemists. The complexity of FTIR characterization comes mainly from the high degree of infrared absorption bands overlapping, that are difficult to be accurately ascribed, despite of the fact that up to date computer-searchable databases of spectra are currently available.

Lamellar-Grating-Based MEMS Fourier Transform Spectrometer

Abstract: Design, fabrication, and characterization of a high-performance micromachined lamellar-grating-interferometer-based Fourier transform spectrometer are presented. The device is designed to give high deflections with very low dynamic deformation and good mode separation. Mechanical self-stoppers are introduced to withstand accelerations larger than 500 g due to shock. The clear aperture area of the grating is about 10 mm2. The maximum deflection while electrostatically actuated at ambient conditions is ±356 μm at 71.2 V and 340 Hz, setting a record for comparable devices. At a pressure of 8.6 Pa, the same deflection is reached at 4.3 V. Six hundred eighty spectra per second can be recorded with a resolution of 14 cm-1. With a HeNe laser at 633 nm, a spectral resolution of 0.54 nm (22 cm-1) is reached using electrostatic actuation. The microelectromechanical systems device is integrated into a compact Fourier transform spectrometer setup including a blackbody source, an infrared (IR) detector, and a visible laser using the device back side for reference. Early results with IR interferograms are also reported. In addition, the devices are actuated with pressure waves in the ambient air to reach deflections up to ±700 μm. With this setup, the spectrum of a red laser is measured with a resolution of 0.3 nm (12.4 cm-1).

General purpose small fourier spectrometers: Design and investigation

Abstract: The main parameters of ΦT-02 and ΦT-10 Fourier spectrometers are presented. The design of the main unit of Fourier spectrometers, a dynamic interferometer, which has coaxial optical channels, is described, and a movable beam splitter is displaced using an electrodynamic drive via a parallelogram mech- anism. The operation of the electrodynamic drive of the beam splitter was investigated. The technique of coherent summation of interferograms was used when processing the measurement results.

Referenced passive spectroscopy using dual frequency combs

Abstract: A referenced passive spectroscopy scheme using infrared frequency combs is presented. We perform a noise analysis and compare the results with a classical Fourier transform spectrometer. Experimental results are shown and great agreement with theory is obtained.

High resolution Fourier transform spectroscopy of HD 16O: Line positions, absolute intensities and self broadening coefficients in the 8800-11,600cm -1 spectral region

Abstract: High-resolution water vapor absorption spectra have been measured at room temperature in the 8800–11,600 cm−1 spectral region. They were obtained using the mobile BRUKER IFS 120M Fourier transform spectrometer (FTS) from ULB-SCQP coupled to the 50 m base long multiple reflection White type cell in GSMA laboratory. The absorption path was 600 m and different H2O/HDO/D2O mixtures were used. Measurements of line positions, intensities and self-broadening coefficients were performed for the HD16O isotopologue. 6464 rovibrational assignment of the observed lines was made on the basis of global variational predictions and allowed the identification of new energy levels. 3ν3, 2ν1+ν3, 3ν1+ν2, ν1+2ν3 and 2ν2+2ν3 are the five strongest bands. The present paper provides a complementary data set on water vapor for atmospheric and astrophysical applications.

Far infrared Fourier-transform spectroscopy of mono-deuterated hydrogen peroxide HOOD

Abstract: We present the gas phase spectrum of singly deuterated hydrogen peroxide, HOOD, in its vibrational ground state, recorded by the high resolution Fourier-transform interferometer located at the AILES synchrotron beamline connected to SOLEIL. More than 1000 transitions in the range from 20 to 143 cm−1 were assigned, leading to a set of preliminary rotational and centrifugal distortion constants determined by least squares fit analysis. All transitions are split by the tunneling motion of a hindered internal rotation. The splitting has been determined to be 5.786(13) cm−1 in the torsional ground state and it shows a dependence on the rotational quantum number Ka. Some perturbations were not treated yet, but the present analysis permits to obtain a preliminary set of parameters.

Broadband near-field mid-infrared spectroscopy and application to phonon resonances in quartz

Abstract: Infrared (IR) spectroscopy is a versatile analytical method and nano-scale spatial resolution could be achieved by scattering type near-field optical microscopy (s-SNOM). The spectral bandwidth was, however, limited to approximately 300 cm−1 with a laser light source. In the present study, the development of a broadband mid-IR near-field spectroscopy with a ceramic light source is demonstrated. A much wider bandwidth (at least 3000 to 1000 cm−1) is achieved with a ceramic light source. The experimental data on quartz Si-O phonon resonance bands are well reproduced by theoretical simulations indicating the validity of the present broadband near-field IR spectroscopy.