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Infrared (IR) Spectroscopy: Overview

Infrared (IR) Spectroscopy: Overview

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.
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IR Spectrometers

IR Spectrometers

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...

IR Spectrum

IR Spectrum

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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IR Frequency Region: Fingerprint Region

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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 C=O, C=N, and C=C occur between 1600–1850 cm−1.
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Applications of IR Spectroscopy: Overview

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The non-destructive nature and ability to provide valuable chemical information make IR spectroscopy a versatile technique with broad applications in various scientific and industrial fields. IR spectroscopy is commonly used to identify and characterize organic and inorganic compounds. It provides information about the functional groups present in a molecule and the bonding between atoms. This helps in the structural elucidation of compounds during organic synthesis, pharmaceutical research,...

IR Spectroscopy: Molecular Vibration Overview

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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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High-definition Fourier Transform Infrared (FT-IR) Spectroscopic Imaging of Human Tissue Sections towards Improving Pathology

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Infrared spectrometry.

|April 8, 2010

Summary

Fourier and Hadamard transform spectroscopy techniques were developed at Johns Hopkins University. This study describes these methods and tunable diode laser spectroscopy for infrared spectral analysis.

Area of Science:

Spectroscopy
Analytical Chemistry
Physical Chemistry

Background:

Early advancements in spectroscopy were pioneered at Johns Hopkins University.
Fourier transform spectroscopy and Hadamard transform spectroscopy represent key developments in spectral analysis.
Infrared (IR) spectroscopy is crucial for molecular identification and characterization.

Purpose of the Study:

To provide a historical overview of early Fourier spectroscopy work at Johns Hopkins University.
To describe the fundamental principles of Fourier and Hadamard transform spectroscopy.
To introduce tunable diode laser spectroscopy and difference frequency techniques for IR spectral studies.

Main Methods:

Historical review of spectroscopic research.

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General description of Fourier transform spectroscopy principles.

Explanation of Hadamard transform spectroscopy methodology.

Overview of tunable diode laser spectroscopy characteristics.

Description of the difference frequency technique for IR analysis.

Main Results:

The historical context of Fourier spectroscopy at Johns Hopkins University is established.
Core concepts and operational principles of Fourier and Hadamard transform spectroscopy are elucidated.
Key features and applications of tunable diode laser spectroscopy and difference frequency techniques are presented.

Conclusions:

Fourier and Hadamard transform spectroscopy are significant spectroscopic techniques.
Tunable diode laser spectroscopy and difference frequency methods offer valuable approaches for IR spectral studies.
This work provides foundational knowledge on several important spectroscopic methods.