Fringes in FTIR spectroscopy revisited: understanding and modelling fringes in infrared spectroscopy of thin films

Konevskikh, Tatiana; Ponossov, Arkadi; Blümel, R.; Lukács, Rozália; Köhler, Achim

doi:10.1039/c4an02343a

Cited by 27 publications

(37 citation statements)

References 34 publications

(62 reference statements)

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“…Contemporary textbooks do not address the possibility that the linear concentration dependence could be fundamentally incorrect. [19][20][21][22][23] In the following, we will briefly introduce why absorbance is not linearly dependent on the concentration, even in the absence of any interactions. [15][16][17][18] The current literature on the correction of "artifacts" and deviations from Beer's law relies on the additivity and general linearity of absorbance.…”

Section: Beer's Law-why Integrated Absorbance Depends Linearly On Conmentioning

confidence: 99%

“…[15][16][17][18] The current literature on the correction of "artifacts" and deviations from Beer's law relies on the additivity and general linearity of absorbance. [19][20][21][22][23] In the following, we will briefly introduce why absorbance is not linearly dependent on the concentration, even in the absence of any interactions. More important, we will show how determining either the integrated absorbance of a band or the classical oscillator strength, instead of the absorbance at a certain spectral point or the peak absorbance, can overcome the corresponding limitation.…”

Section: Beer's Law-why Integrated Absorbance Depends Linearly On Conmentioning

confidence: 99%

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Beer's Law‐Why Integrated Absorbance Depends Linearly on Concentration

2019

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As derived by Max Planck in 1903 from dispersion theory, Beer's law has a fundamental limitation. The concentration dependence of absorbance can deviate from linearity, even in the absence of any interactions or instrumental nonlinearities. Integrated absorbance, not peak absorbance, depends linearly on concentration. The numerical integration of the absorbance leads to maximum deviations from linearity of less than 0.1 %. This deviation is a consequence of a sum rule that was derived from the Kramers‐Kronig relations at a time when the fundamental limitation of Beer's law was no longer mentioned in the literature. This sum rule also links concentration to (classical) oscillator strengths and thereby enables the use of dispersion analysis to determine the concentration directly from transmittance and reflectance measurements. Thus, concentration analysis of complex samples, such as layered and/or anisotropic materials, in which Beer's law cannot be applied, can be achieved using dispersion analysis.

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Section: Beer's Law-why Integrated Absorbance Depends Linearly On Conmentioning

confidence: 99%

Section: Beer's Law-why Integrated Absorbance Depends Linearly On Conmentioning

confidence: 99%

Beer's Law‐Why Integrated Absorbance Depends Linearly on Concentration

2019

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“…However, neither of these methods was effective in reducing amplitudes of some of the very large interference fringes sufficiently to detect small OH absorption bands. We had greater success reducing interference fringes by fitting them where the baseline was free of absorption bands, using DatLab software (similar to fringe modeling of Clark and Moffatt, 1978;Pistorius and DeGrip, 2004;Konevskikh et al, 2015), and subtracting the model fringes from the spectral data. This improved the quality of spectra when interference fringes had modest amplitudes, but interference fringes for thin samples were very large and resulting backgrounds were sufficiently irregular that we could not resolve small OH absorption bands.…”

Section: Interference Fringesmentioning

confidence: 99%

Synchrotron FTIR imaging of OH in quartz mylonites

et al. 2017

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Abstract. Previous measurements of water in deformed quartzites using conventional Fourier transform infrared spectroscopy (FTIR) instruments have shown that water contents of larger grains vary from one grain to another. However, the non-equilibrium variations in water content between neighboring grains and within quartz grains cannot be interrogated further without greater measurement resolution, nor can water contents be measured in finely recrystallized grains without including absorption bands due to fluid inclusions, films, and secondary minerals at grain boundaries.Synchrotron infrared (IR) radiation coupled to a FTIR spectrometer has allowed us to distinguish and measure OH bands due to fluid inclusions, hydrogen point defects, and secondary hydrous mineral inclusions through an aperture of 10 µm for specimens > 40 µm thick. Doubly polished infrared (IR) plates can be prepared with thicknesses down to 4-8 µm, but measurement of small OH bands is currently limited by strong interference fringes for samples < 25 µm thick, precluding measurements of water within individual, finely recrystallized grains. By translating specimens under the 10 µm IR beam by steps of 10 to 50 µm, using a software-controlled x − y stage, spectra have been collected over specimen areas of nearly 4.5 mm 2 . This technique allowed us to separate and quantify broad OH bands due to fluid inclusions in quartz and OH bands due to micas and map their distributions in quartzites from the Moine Thrust (Scotland) and Main Central Thrust (Himalayas).Mylonitic quartzites deformed under greenschist facies conditions in the footwall to the Moine Thrust (MT) exhibit a large and variable 3400 cm −1 OH absorption band due to molecular water, and maps of water content corresponding to fluid inclusions show that inclusion densities correlate with deformation and recrystallization microstructures. Quartz grains of mylonitic orthogneisses and paragneisses deformed under amphibolite conditions in the hanging wall to the Main Central Thrust (MCT) exhibit smaller broad OH bands, and spectra are dominated by sharp bands at 3595 to 3379 cm −1 due to hydrogen point defects that appear to have uniform, equilibrium concentrations in the driest samples. The broad OH band at 3400 cm −1 in these rocks is much less common. The variable water concentrations of MT quartzites and lack of detectable water in highly sheared MCT mylonites challenge our understanding of quartz rheology. However, where water absorption bands can be detected and compared with deformation microstructures, OH concentration maps provide information on the histories of deformation and recovery, evidence for the introduction and loss of fluid inclusions, and water weakening processes.

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“…The only visible peak is a broad FT-IR peak between 600 and 900 cm −1 and a wavy background between 1300 and 3000 cm −1 . The background pattern originates from the small thickness of the films and internal reflections that give rise to a wavy sinusoidal background pattern59. The broad peak between 600 and 900 cm −1 originates from the partial transformation of silica from tetrahedral to octahedral coordination.…”

Section: Resultsmentioning

confidence: 99%

Ion irradiation induced structural modifications and increase in elastic modulus of silica based thin films

Shojaee

Wang

et al. 2017

Sci Rep

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Ion irradiation is an alternative to heat treatment for transforming organic-inorganic thin films to a ceramic state. One major shortcoming in previous studies of ion-irradiated films is the assumption that constituent phases in ion-irradiated and heat-treated films are identical and that the ion irradiation effect is limited to changes in composition. In this study, we investigate the effects of ion irradiation on both the composition and structure of constituent phases and use the results to explain the measured elastic modulus of the films. The results indicated that the microstructure of the irradiated films consisted of carbon clusters within a silica matrix. It was found that carbon was present in a non-graphitic sp2-bonded configuration. It was also observed that ion irradiation caused a decrease in the Si-O-Si bond angle of silica, similar to the effects of applied pressure. A phase transformation from tetrahedrally bonded to octahedrally bonded silica was also observed. The results indicated the incorporation of carbon within the silica network. A combination of the decrease in Si-O-Si bond angle and an increase in the carbon incorporation within the silica network was found to be responsible for the increase in the elastic modulus of the films.

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Fringes in FTIR spectroscopy revisited: understanding and modelling fringes in infrared spectroscopy of thin films

Cited by 27 publications

References 34 publications

Beer's Law‐Why Integrated Absorbance Depends Linearly on Concentration

Beer's Law‐Why Integrated Absorbance Depends Linearly on Concentration

Synchrotron FTIR imaging of OH in quartz mylonites

Ion irradiation induced structural modifications and increase in elastic modulus of silica based thin films

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