Comments on “A Common Misunderstanding about the Voigt Line Profile”

Schreier, Franz

doi:10.1175/2009jas2906.1

Cited by 7 publications

(2 citation statements)

References 24 publications

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“…The amounts of the different BAS were determined on the basis of the quantitative deconvolution of the 3610 cm –1 band. This was performed using six Voigt functions, as these functions describe most accurately the combination of the Gaussian and Lorentzian components that arise due to chemical inhomogeneity of the nearest neighbors of BAS and collision-like broadening caused by perturbation with hydrogen bonds. ,− Every band was defined by four parameters: position, width, fraction of the Lorentzian component, and intensity. During the deconvolution, however, only intensities of the single bands were optimized, while the positions, widths, and Lorentzian fractions were predetermined.…”

Section: Resultsmentioning

confidence: 99%

Insights into Brønsted Acid Sites in the Zeolite Mordenite

et al. 2014

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The unique feature of the zeolite catalysts is the presence of catalytically active acidic hydroxyls, also known as Brønsted acid sites (BAS), in the zeolite micropores of molecular dimensions. The accessibility and catalytic properties of BAS depend on their local environment, and it is therefore important to know the exact locations of BAS and the number of BAS in these locations. This paper reports a detailed FT-IR investigation into BAS present in the acidic and partially Na-exchanged samples of industrially important mordenite (MOR) zeolite. Our results demonstrate the existence of (at least) six distinct BAS that can be visualized by six single bands in Fourier self-deconvolution traces of the IR spectra. The quantitative estimates for the amounts of these distinct BAS were obtained using the six-band deconvolution method developed in this work. These estimates show that in the purely acidic H-MOR sample about 25% of BAS are located in eight-membered ring (8-MR) channels (O1−H and O9−H hydroxyls), ∼13% of BAS are at the intersections between the side pockets and 12-MR channels (O5−H hydroxyls), and ∼62% of BAS are located in 12-MR channels (∼39% correspond to O2−H and/or O10−H hydroxyls and the remaining 23% to O3−H and O7−H hydroxyls). These quantitative data demonstrate that the acid sites are distributed quite evenly between oxygen atoms in different crystallographic positions, thus revealing the complexity of the experimental identification of distinct BAS in mordenites and explaining the variety of the earlier suggestions regarding their positions in these zeolites.

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Section: Resultsmentioning

confidence: 99%

Insights into Brønsted Acid Sites in the Zeolite Mordenite

et al. 2014

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“…These combined effects are described by the Voigt profile, which is the convolution of the Lorentzian and Gaussian profiles. [ 33–35 ] In this work, for a given isomer, each spectral peak is convoluted with the Voigt profile, V ik ( ω , σ , γ ), where i refers to the number of peaks, and k refers to the number of possible isomers. The Voigt profile used in this work is a convolution of normalized and centered Lorentzian and Gaussian profiles defined, respectively, in Equations ) and ):

L_{ik} ((),, ω, γ) = \frac{γ}{π} \frac{1}{{(ω - ω_{italicik})}^{2} + γ^{2}},

and

G_{ik} ((),, ω, σ) = \frac{1}{σ \sqrt{π}} \exp ([], - \frac{{((), ω - ω_{ik})}^{2}}{σ^{2}}),

where ω ik is the center of the i th peak of k th isomer.…”

Section: Methodsmentioning

confidence: 99%

Theoretical infrared spectrum of the ethanol hexamer

Malloum

Fifen

Conradie

2020

Int J of Quantum Chemistry

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The hydrogen bond network of ethanol clusters is among the most complex hydrogen bond networks of molecular clusters. One of the reasons of its complexity arises from the number of possible ethanol monomers (there are three isoenergetic isomers of the ethanol monomer). This leads to difficulties in the exploration of potential energy surfaces (PESs) of ethanol clusters. In this work, we have explored the PES of the ethanol hexamer at the MP2/aug-cc-pVDZ level of theory. We have provided structures and their relative stability at 0 K and for temperatures ranging from 20 to 400 K in the gas phase. These structures are used to compute the theoretical infrared (IR) spectrum of the ethanol hexamer at the MP2/aug-cc-pVDZ level of theory. As a result, 98 different structures have been investigated, and six isomers are reported to be the most isoenergetically stable structures of the ethanol hexamer. These isomers are folded cyclic structures in which the stability is enhanced by the implication of CHÁ Á ÁO interactions. Our investigations show that the PES of the ethanol hexamer is very flat, yielding several isoenergetic structures. Furthermore, we have noted that several isomers contribute to the population of the ethanol hexamer at high temperatures. As far as the IR spectroscopic study is concerned, we have found that the IR spectra of the most stable structures are in good agreement with the experiment.Considering this agreement, these structures are used to assign the experimental peaks in the CH-stretching region. We concluded that the stability of the structures of the ethanol hexamer is related both to OHÁ Á ÁO hydrogen bonds and CHÁ Á ÁO interactions. Overall, we have found that the IR spectrum of the ethanol hexamer, calculated from the contribution of all the possible stable structures weighted by their probability, excellently reproduce the experimental spectrum of the ethanol hexamer. K E Y W O R D S ethanol clusters, ethanol hexamer, infrared spectrum, relative population, Voigt profile 1 | INTRODUCTIONLiquid ethanol has important applications in industries, and it is widely used as a solvent in chemical processes. Besides, ethanol has many applications in medicine and pharmacology. [1] Understanding of some properties of liquid ethanol is related to the hydrogen bond networks of ethanol clusters (EtOH) n . The hydrogen bond networks of the ethanol clusters are among the most complex hydrogen bond networks in molecular clusters. One of the reasons of this complexity is the high number of possible stable structures of the ethanol monomer (there are three isoenergetic isomers of the ethanol monomer: gauche−, trans, and gauche+ related to the value of the CCOH dihedral angles −60 , 180 , and +60 , respectively). [2][3][4] Most of the investigations performed on ethanol clusters are limited to the ethanol dimer due to difficulties arising from the exploration of the potential energy surfaces (PESs) of the ethanol clusters. [2,3,[5][6][7][8][9][10][11] Reliable investigations performed on the ethanol dimer,

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Optimized implementations of rational approximations for the Voigt and complex error function

Schreier

2011

Journal of Quantitative Spectroscopy and Radiative Transfer

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Comments on “A Common Misunderstanding about the Voigt Line Profile”

Cited by 7 publications

References 24 publications

Insights into Brønsted Acid Sites in the Zeolite Mordenite

Insights into Brønsted Acid Sites in the Zeolite Mordenite

Theoretical infrared spectrum of the ethanol hexamer

Optimized implementations of rational approximations for the Voigt and complex error function

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