Extracting pure absorbance spectra in infrared microspectroscopy by modeling absorption bands as Fano resonances

Absorbance and first and second derivative absorbance spectra and quarter-millimolar absorptivity coefficients for hemoglobin species including oxy-, deoxy-, carboxy- and methemoglobin in the visible and in the near infrared regions from 620 nm to 2500 nm are presented. At wavelengths longer than 1500 nm, the absorbance and second derivative absorbance spectra of hemoglobin species are similar for all of the species. Absorption bands are present centred at 1690, 1740, 2056, 2170, 2290 and 2350 nm.

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Infrared Analysis of Particulates by FT-IR Emission/Transmission Spectroscopy

Applied Spectroscopy ◽

10.1366/0003702864508421 ◽

1986 ◽

Vol 40 (6) ◽

pp. 746-759 ◽

Cited By ~ 12

Author(s):

Peter R. Solomon ◽

Robert M. Carangelo ◽

David G. Hamblen ◽

Philip E. Best

Keyword(s):

Liquid Droplet ◽

Infrared Absorption Spectrum ◽

Chemical Characterization ◽

Quantitative Agreement ◽

Infrared Analysis ◽

Absorption Bands ◽

Additional Advantage ◽

Ft Ir ◽

Ir Emission ◽

Absorbance Spectra

In this paper we report on a new method for the on-line chemical characterization of gas-suspended particulate and liquid droplet streams. The method is a combination of emission and transmission (E/T) spectroscopy performed using a Fourier transform infrared (FT-IR) spectrometer and a cell which allows analysis of room-temperature particulates surrounded by hot walls. The method was based on the discovery that the spectrum of radiation coming from such particles contained structure corresponding to the infrared absorption spectrum of the particulates. It was determined that the observed energy was wall radiation which reaches the detector after refraction by, and transmission through the particles. The shape of the observed spectrum relative to that of the wall spectrum is reduced at the absorption bands of the particulates. The general concepts of the E/T method were validated by samples with sizes varying from a few to several hundred microns with varying optical properties. For solids, excellent results were achieved for composition measurements. For a sample of known particle size, quantitative absorbance spectra were obtained from the E/T spectra with the use of a model based on ray optics. The spectra were in good quantitative agreement with absorbance spectra derived by the KBr pellet method for the same sample thickness. The E/T derived spectra were somewhat noisier than the KBr pellet spectra, but were free of Christiansen effect band distortions and scattering contributions. The E/T method has the additional advantage of requiring little or no sample preparation.

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Ultraviolet Spectroscopic Study of Ferric Iron Solutions

Applied Spectroscopy ◽

10.1366/0003702804730394 ◽

1980 ◽

Vol 34 (3) ◽

pp. 377-380 ◽

Cited By ~ 6

Author(s):

Mary F. Brown ◽

Dana R. Kester

Keyword(s):

Ionic Strength ◽

Ferric Iron ◽

Gaussian Function ◽

Low Ph ◽

Absorption Bands ◽

Experimental Conditions ◽

Band Maximum ◽

Ultraviolet Absorbance ◽

Constant Ph ◽

Absorbance Spectra

Ultraviolet absorbance spectra of ferric iron solutions of varying iron concentrations maintained at a constant pH of 1.0 and a constant ionic strength of 0.1 were studied. The experimental conditions of low pH minimized the formation of the hydrolytic FeOH2+ and Fe(OH)2+ species; thus, the spectra of iron solutions containing principally the Fe3+ species were recorded. The digitized spectral data were used to establish a model for the Fe3+ absorption spectrum that involves a Gaussian function with three parameters for each of the two absorption bands. These parameters were the wavenumber of the band maximum, ν̄max, the full width at half maximum intensity, Δν̄1/2, and the absorptivity of the band maximum, εmax. This study provided estimates for these parameters at 25°C for 0.1 ionic strength media.

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Anisotropy of 3D Columnar Coatings in Mid-Infrared Spectral Range

Nanomaterials ◽

10.3390/nano11123247 ◽

2021 ◽

Vol 11 (12) ◽

pp. 3247

Author(s):

Lina Grineviciute ◽

Soon Hock Ng ◽

Molong Han ◽

Tania Moein ◽

Vijayakumar Anand ◽

...

Keyword(s):

Angular Dependence ◽

Field Enhancement ◽

Absorption Bands ◽

Mid Infrared ◽

Infrared Microspectroscopy ◽

Enhanced Absorption ◽

Glancing Angle ◽

Infrared Spectral ◽

Stretching Vibration ◽

Polarisation Analysis

Polarisation analysis in the mid-infrared fingerprint region was carried out on thin (∼1 μm) Si and SiO2 films evaporated via glancing angle deposition (GLAD) method at 70∘ to the normal. Synchrotron-based infrared microspectroscopic measurements were carried out on the Infrared Microspectroscopy (IRM) beamline at Australian Synchrotron. Specific absorption bands, particularly Si-O-Si stretching vibration, was found to follow the angular dependence of ∼cos2θ, consistent with the absorption anisotropy. This unexpected anisotropy stems from the enhanced absorption in nano-crevices, which have orientation following the cos2θ angular dependence as revealed by Fourier transforming the image of the surface of 3D columnar films and numerical modeling of light field enhancement by sub-wavelength nano-crevices.

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Anisotropy of 3D Columnar Coatings in Mid-Infrared Spectral Range

10.20944/preprints202110.0280.v1 ◽

2021 ◽

Author(s):

Lina Grineviciute ◽

Soon Hock Ng ◽

Molong Han ◽

Tania Moein ◽

Vijayakumar Anand ◽

...

Keyword(s):

Angular Dependence ◽

Field Enhancement ◽

Absorption Bands ◽

Mid Infrared ◽

Infrared Microspectroscopy ◽

Enhanced Absorption ◽

Glancing Angle ◽

Infrared Spectral ◽

Stretching Vibration ◽

Polarisation Analysis

Polarisation analysis in the mid-infrared fingerprint region was carried out on thin (&sim;1μm) Si and SiO2 films evaporated via glancing angle deposition (GLAD) method at 70∘ to the normal. Synchrotron-based infrared microspectroscopic measurements were carried out on the Infrared Microspectroscopy (IRM) beamline at Australian Synchrotron. Specific absorption bands, particularly Si-O-Si stretching vibration, was found to follow the angular dependence of &sim;cos2θ, consistent with the absorption anisotropy. This unexpected anisotropy stems from the enhanced absorption in nano-crevices, which have orientation following the cos2θ angular dependence as revealed by Fourier transforming the image of the surface of 3D columnar films and numerical modeling of light field enhancement by sub-wavelength nano-crevices.

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The effect of deformation of absorbing scatterers on Mie-type signatures in infrared microspectroscopy

Scientific Reports ◽

10.1038/s41598-021-84064-5 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Maren Anna Brandsrud ◽

Reinhold Blümel ◽

Johanne Heitmann Solheim ◽

Achim Kohler

Keyword(s):

Electromagnetic Radiation ◽

Biological Samples ◽

Numerical Aperture ◽

Iterative Algorithms ◽

Shape Resonance ◽

Chaotic Scattering ◽

Extinction Efficiency ◽

Infrared Microspectroscopy ◽

Spherical Scatterer ◽

Absorbance Spectra

AbstractMie-type scattering features such as ripples (i.e., sharp shape-resonance peaks) and wiggles (i.e., broad oscillations), are frequently-observed scattering phenomena in infrared microspectroscopy of cells and tissues. They appear in general when the wavelength of electromagnetic radiation is of the same order as the size of the scatterer. By use of approximations to the Mie solutions for spheres, iterative algorithms have been developed to retrieve pure absorbance spectra. However, the question remains to what extent the Mie solutions, and approximations thereof, describe the extinction efficiency in practical situations where the shapes of scatterers deviate considerably from spheres. The aim of the current study is to investigate how deviations from a spherical scatterer can change the extinction properties of the scatterer in the context of chaos in wave systems. For this purpose, we investigate a chaotic scatterer and compare it with an elliptically shaped scatterer, which exhibits only regular scattering. We find that chaotic scattering has an accelerating effect on the disappearance of Mie ripples. We further show that the presence of absorption and the high numerical aperture of infrared microscopes does not explain the absence of ripples in most measurements of biological samples.

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Polarimetric Observations of Red Variables: A Study of Gas and Particle Interactions

International Astronomical Union Colloquium ◽

10.1017/s0252921100073668 ◽

1979 ◽

Vol 46 ◽

pp. 386-408 ◽

Cited By ~ 2

Author(s):

G. V. Coyne ◽

I. S. McLean

Keyword(s):

Wavelength Dependence ◽

Stellar Atmosphere ◽

Molecular Absorption ◽

Absorption Bands ◽

Absorption And Emission ◽

Mira Variables ◽

Stellar Photosphere ◽

Regular Variable ◽

Red Supergiants ◽

Balmer Lines

AbstractIn recent years the wavelength, dependence of the polarization in a number of Mira variables, semi-regular variables and red supergiants has been measured with resolutions between 0.3 and 300 A over the range 3300 to 11000 A. Variations are seen across molecular absorption bands, especially TiO bands, and across atomic absorption and emission lines, especially the Balmer lines. In most cases one can ignore or it is possible to eliminate the effects due to interstellar polarization, so that one can study the polarization mechanisms operating in the stellar atmosphere and environment. The stars Omicron Ceti. (Mira), V CVn (semi-regular variable) and Mu Cephei (M2 la), in addition to other stars similar to them, will be discussed in some detail.Models to explain the observed polarization consider that the continuum flux is polarized either by electron, molecular and/or grain scattering or by temperature variations and/or geometrical asymmetries over the stellar photosphere. This polarized radiation is affected by atomic and molecular absorption and emission processes at various geometric depths in the stellar atmosphere and envelope. High resolution spectropolarimetry promises, therefore, to be a power-rul tool for studying stratification effects in these stars.

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FR-IR Molecular Microanalysis System

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100134958 ◽

1990 ◽

Vol 48 (2) ◽

pp. 270-271

Author(s):

John A. Reffner ◽

William T. Wihlborg

Keyword(s):

Fourier Transform ◽

Fourier Transform Infrared ◽

Integrated System ◽

Morphological Examination ◽

Fully Integrated ◽

Ir Microscopy ◽

Normal Functions ◽

Infrared Microspectroscopy ◽

Infrared Spectral ◽

Ft Ir

The IRμs™ is the first fully integrated system for Fourier transform infrared (FT-IR) microscopy. FT-IR microscopy combines light microscopy for morphological examination with infrared spectroscopy for chemical identification of microscopic samples or domains. Because the IRμs system is a new tool for molecular microanalysis, its optical, mechanical and system design are described to illustrate the state of development of molecular microanalysis. Applications of infrared microspectroscopy are reviewed by Messerschmidt and Harthcock.Infrared spectral analysis of microscopic samples is not a new idea, it dates back to 1949, with the first commercial instrument being offered by Perkin-Elmer Co. Inc. in 1953. These early efforts showed promise but failed the test of practically. It was not until the advances in computer science were applied did infrared microspectroscopy emerge as a useful technique. Microscopes designed as accessories for Fourier transform infrared spectrometers have been commercially available since 1983. These accessory microscopes provide the best means for analytical spectroscopists to analyze microscopic samples, while not interfering with the FT-IR spectrometer’s normal functions.

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