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Infrared (IR) Spectroscopy: Overview01:09

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When electromagnetic radiation passes through a material, atoms or molecules transition from a lower to a higher energy state by absorbing radiation corresponding to the energy difference between the two states. The absorption of infrared (IR) radiation causes transitions between vibrational energy levels in a molecule. Therefore, IR spectroscopy is a useful analytical tool for determining the molecular structure of molecules.
Different compounds display unique properties due to their...
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IR Spectrometers01:25

IR Spectrometers

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There are two main infrared (IR) spectrophotometers: dispersive IR spectrometers and Fourier transform infrared (FTIR) spectrometers. In a dispersive IR spectrometer, a beam of infrared radiation produced by a hot wire is divided into two parallel equal-intensity beams using mirrors. One beam passes through the sample, while another is a reference beam. The beams then move through the monochromator, which separates the radiations into a continuous spectrum of different frequencies. The...
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IR Spectrum01:19

IR Spectrum

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When infrared (IR) radiation passes through a molecule, the bonds stretch or bend by absorbing the radiation. This absorption creates the molecule's absorption spectrum, which is the plot of its percentage transmittance versus wavenumber.
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Attenuated Total Reflectance (ATR) Infrared Spectroscopy: Overview01:13

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Attenuated total reflectance (ATR) infrared spectroscopy is a powerful analytical technique used to study the composition of materials. It is widely employed in chemistry, materials science, forensic science, and other fields where sample characterization is required. ATR has several advantages over traditional transmission IR spectroscopy, including the requirement of little to no sample preparation and the ability to analyze a wide range of samples.
The ATR process begins by directing a beam...
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IR Spectroscopy: Molecular Vibration Overview01:24

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When Infrared (IR) radiation passes through a covalently bonded molecule, the bonds transition from lower to higher vibrational levels. The fundamental vibrational motions that result in infrared absorption can be classified as stretching or bending vibrations.
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IR Frequency Region: Fingerprint Region01:03

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IR spectra are divided into two main regions: the diagnostic region and the fingerprint region. The diagnostic region of the spectrum lies above 1500 cm−1. The absorptions resulting from single-bond vibrations of the N–H, C–H, and O–H stretch at higher wavenumbers and appear on the left side of the spectrum. The stretching absorptions of the C≡C and C≡N occur between 2100–2300 cm−1. In contrast, those arising from stretching absorptions of the...
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Infrared Refraction Spectroscopy.

Thomas G Mayerhöfer1,2, Vladimir Ivanovski3, Jürgen Popp1,2

  • 1Spectroscopy and Imaging, Leibniz Institute of Photonic Technology (IPHT), Jena, Germany.

Applied Spectroscopy
|August 18, 2021
PubMed
Summary
This summary is machine-generated.

We introduce Infrared Refraction Spectroscopy, a novel technique complementary to absorption spectroscopy. This method simplifies quantitative analysis of reflectance spectra, offering a new tool for chemical concentration measurements.

Keywords:
Beer’s lawReflection spectroscopyrefraction spectroscopy

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Area of Science:

  • Spectroscopy
  • Analytical Chemistry
  • Optics

Background:

  • Absorption spectroscopy is a primary tool for quantitative analysis.
  • Interpreting reflectance spectra quantitatively often requires complex methods.
  • A gap exists in simple, quantitative analysis of reflectance data.

Purpose of the Study:

  • Introduce Infrared Refraction Spectroscopy (IRS) as a complementary technique.
  • Develop a simple method for quantitative interpretation of reflectance spectra.
  • Address limitations of baseline ambiguities in absorbance spectra.

Main Methods:

  • Calculate refractive index spectra from reflectance spectra, neglecting absorption.
  • Numerically derive refractive index spectra to obtain features similar to second derivative absorbance spectra.
  • Utilize differences in refractive index values to correlate with concentration.

Main Results:

  • Refractive index changes are proportional to concentration.
  • Derived spectra peak values indicate oscillator positions and correlate with concentration.
  • First derivative refractive index spectra show no baseline ambiguities, unlike absorbance spectra.
  • A simple difference of refractive index values correlates linearly with concentration.

Conclusions:

  • Infrared Refraction Spectroscopy offers a simple and quantitative method for analyzing reflectance spectra.
  • IRS provides a valuable alternative to absorption spectroscopy, particularly for complex samples.
  • The technique simplifies concentration determination without baseline issues common in absorbance methods.