Search results for "Fourier transform"
showing 10 items of 1138 documents
Fourier-transform spectroscopy and deperturbation analysis of the spin-orbit coupled A(1)Σ(+) and b(3)Π states of KRb.
2016
Fourier-transform A(1)Σ(+) - b(3)Π → X(1)Σ(+) laser-induced fluorescence spectra were recorded for the natural mixture of (39,41)K(85,87)Rb isotopologues produced in a heatpipe oven. Overall 4200 rovibronic term values of the spin-orbit coupled A(1)Σ(+) and b(3)Π states were determined with an uncertainty of about 0.01 cm(-1) in the energy range [10 850, 14 200] cm(-1) covering rotational quantum numbers J' ∈ [3, 280]. Direct deperturbation analysis of the A ∼ b complex performed within the framework of the A(1)Σ(+) ∼ b(3)ΠΩ=0,1,2 coupled-channel approach reproduced experimental data with a standard deviation of 0.004 cm(-1). Initial parameters of the internuclear potentials and spin-orbit …
Heterogeneous Interactions between Gas-Phase Pyruvic Acid and Hydroxylated Silica Surfaces: A Combined Experimental and Theoretical Study
2019
The adsorption of gas-phase pyruvic acid (CH3COCOOH) on hydroxylated silica particles has been investigated at 296 K using transmission Fourier transform infrared (FTIR) spectroscopy and theoretical simulations. Under dry conditions (<1% relative humidity, RH), both the trans-cis (Tc) and trans-trans (Tt) pyruvic acid conformers are observed on the surface as well as the (hydrogen bonded) pyruvic acid dimer. The detailed surface interactions were further understood through ab initio molecular dynamics simulations. Under higher relative humidity conditions (above 10% RH), adsorbed water competes for surface adsorption sites. Adsorbed water is also observed to change the relative populations …
Matrix isolation and quantum chemical studies on the H2O2–SO2complex
2004
Complexation and photochemical reactions of hydrogen peroxide and sulfur dioxide have been studied in solid Ar, Kr and Xe. Complexes between H2O2 and SO2 are characterized using Fourier transform infrared spectroscopy and ab initio calculations. In solid Ar, the H2O2–SO2 complex absorptions are found at wavenumbers of 3572.8, 3518.7, 3511.2, 3504.3, 1340.3, 1280.2 and 1149.9 cm−1. In Kr and Xe matrices, the bonded OH stretching frequencies deviate from the values in Ar, and we propose that the matrix surrounding influences the structure of the H2O2–SO2 complex. UV photolysis of the H2O2–SO2 was also studied in solid Ar, Kr and Xe. This photolysis produces mainly a complex between sulfur tri…
Equipping metallo-supramolecular macrocycles with functional groups: Assemblies of pyridine-substituted urea ligands
2012
A series of di-(m-pyridyl)-urea ligands were prepared and characterized with respect to their conformations by NOESY experiments and crystallography. Methyl substitution in different positions of the pyridine rings provides control over the position of the pyridine N atoms relative to the urea carbonyl group. The ligands were used to self-assemble metallo-supramolecular M(2)L(2) and M(3)L(3) macrocycles which are generated in a finely balanced equilibrium in DMSO and DMF according to DOSY NMR experiments and ESI FTICR mass spectrometry. Again, crystallography was used to characterize the assemblies. Methyl substitution in positions next to the pyridine nitrogen prevents coordination, while …
Corrosion inhibition performance of a structurally well-defined 1,2,3-triazole derivative on mild steel-hydrochloric acid interface
2021
Abstract In the present work, a new 1,4-disubstituted-1,2,3-triazole product, named 4-[1-(4-methoxy-phenyl)-1H-[1,2,3]triazol-4-ylmethyl]-morpholine (MPTM) was successfully synthesized under click chemistry regime. The structure of the new compound that has a rigid triazole moiety and a flexible morpholine ligand has been characterized using 1H NMR, 13C NMR, HRMS, and FTIR spectroscopy. Its inhibition performance for mild steel in acidic medium 1 M HCl has been studied by utilizing a combination of experimental, spectroscopic and computational methods. The electrochemical characterization was carried out by a gravimetric study, electrochemical impedance spectroscopy (EIS), and potentiodynam…
Efficient remote sensing image classification with Gaussian processes and Fourier features
2017
This paper presents an efficient methodology for approximating kernel functions in Gaussian process classification (GPC). Two models are introduced. We first include the standard random Fourier features (RFF) approximation into GPC, which largely improves the computational efficiency and permits large scale remote sensing data classification. In addition, we develop a novel approach which avoids randomly sampling a number of Fourier frequencies, and alternatively learns the optimal ones using a variational Bayes approach. The performance of the proposed methods is illustrated in complex problems of cloud detection from multispectral imagery.
High-resolution spectroscopy and analysis of the nu3/2nu4 dyad of CF4
2011
International audience; CF4 is a strong greenhouse gas of both anthropogenic and natural origin [D.R. Worton et al., Environ. Sci. Technol. 41, 2184 (2007)]. However, high-resolution infrared spectroscopy of this molecule has received only a limited interest up to now. Until very recently, the public databases only contained cross-sections for this species, but no detailed line list. We reinvestigate here the strongly absorbing ν3 region around 7.8 μm. New Fourier transform infrared (FTIR) spectra up to a maximal resolution of 0.0025 cm−1 have been recorded: (i) room-temperature spectra in a static cell and (ii) a supersonic expansion jet spectrum at a 23 K estimated temperature. Following …
Plastic ingestion by pelagic and demersal fish from the North Sea and Baltic Sea
2015
Plastic ingestion by marine biota has been reported for a variety of different taxa. In this study, we investigated 290 gastrointestinal tracts of demersal (cod, dab and flounder) and pelagic fish species (herring and mackerel) from the North and Baltic Sea for the occurrence of plastic ingestion. In 5.5% of all investigated fishes, plastic particles were detected, with 74% of all particles being in the microplastic (<5mm) size range. The polymer types of all found particles were analysed by means of Fourier transform infrared (FT-IR) spectroscopy. Almost 40% of the particles consisted of polyethylene (PE). In 3.4% of the demersal and 10.7% of the pelagic individuals, plastic ingestion was …
Characterisation of the magmatic signature in gas emissions from Turrialba Volcano, Costa Rica
2014
The equilibrium composition of volcanic gases with their magma is often overprinted by interaction with a shallow hydrothermal system. Identifying the magmatic signature of volcanic gases is critical to relate their composition to properties of the magma (temperature, fO2, gas-melt segregation depth). We report measurements of the chemical composition and flux of the major gas species emitted from Turrialba Volcano during March 2013. Measurements were made of two vents in the summit region, one of which opened in 2010 and the other in 2012. We determined an average SO2 flux of 5.2 ± 1.9 kg s-1 using scanning ultraviolet spectroscopy, and molar proportions of H2O, CO2, SO2, HCl, CO and H2 ga…
Production of extracellular fructans by Gluconobacter nephelii P1464.
2015
UNLABELLED Bacterial extracellular fructans, known as levans, have potential applications in food, pharmaceutical and cosmetic industries and high fructan producing strains could contribute into the cost reduction and more extensive commercial usage of them. An acetic acid bacteria (AAB) isolate P1464 was obtained from the Microbial Strain Collection of Institute of Microbiology and Biotechnology, University of Latvia and identified as Gluconobacter nephelii by DNA-DNA hybridization and the formation of extracellular fructans by this strain was confirmed. Isolated extracellular fructose polymers were characterized using FT-IR spectroscopy and the structural features of fructan appeared as s…