Gourt > Science > Chemistry > Analytical > Infrared Spectroscopy (1)
Infrared spectroscopy (IR Spectroscopy) is the subset of spectroscopy that deals with the Infrared part of the electromagnetic spectrum. This covers a range of techniques, with the most common type by far being a form of absorption spectroscopy. As with all spectroscopic techniques, it can be used to identify a compound and to investigate the composition of a sample.
Theory
The infrared portion of the electromagnetic spectrum is divided into three regions; the near-, mid- and far- infrared, named for their relation to the visible spectrum. The far-infrared, (approx. 400-10 cm-1) lying adjacent to the microwave region, has low energy and may be used for rotational spectroscopy. The mid- infrared (approx. 4000-400 cm-1) may be used to study the fundamental vibrations and associated rotational-vibational structure, whilst the higher energy near-IR (14000-4000 cm-1) can excite overtone or harmonic vibrations.
Infrared spectroscopy works because chemical bonds have specific frequencies at which they vibrate corresponding to energy levels. The resonant frequencies or vibrational frequencies are determined by the shape of the molecular potential energy surfaces, the masses of the atoms and, eventually by the associated vibronic coupling. In order for a vibrational mode in a molecule to be IR active, it must be associated with changes in the permanent dipole. In particular, in the Born-Oppenheimer and harmonic approximations, i.e. when the molecular Hamiltonian corresponding to the electronic ground state can be approximated by a harmonic oscillator in the neighborhood of the equilibrium molecular geometry, the resonant frequencies are determined by the normal modes corresponding to the molecular electronic ground state potential energy surface. Nevertheless, the resonant frequencies can be in a first approach related to the strength of the bond, and the mass of the atoms at either end of it. Thus, the frequency of the vibrations can be associated with a particular bond type.
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ComSpec3D - An online tool for calculation and visualisation of infrared and Raman spectroscopic results, with normal mode information.
Meta Description: [ Calculation and Visualization of Ir and Raman spectra and normal modes ]
CytoSpec Inc. - Software for the analysis of infrared spectral maps including chemical mapping, cluster mapping, PCA and ANN imaging. Includes glossary, downloads and contacts in Croton-on-Hudson, NY.
Meta Description: [ CytoSpec - a Software Solution for Hyperspectral Imaging. Download an Evaluation Copy or View the CytoSpec Online Help. ]
Dr. Georgiou Lab of Analytical Chemistry - Research into olive oil analysis, pesticides formulation analysis, flow injection, using analytical Raman spectroscopy and biosensors, at the Agricultural University of Athens, Greece.
Meta Description: [ Professor Georgiou developes flow injection analytical methods to assess olive oil and food quality, and automate binding studies of cyclodextrins and proteins with micromolecules by gradient techniques. FT-Raman methods for pesticide analysis ]
Infrared and Raman Spectra Interpretation by Group Frequencies - Five days of lectures in the field coupled with FT-IR laboratories and workshops at Stevenson Science Center, organized by the Fisk Inrared Institute in Nashville, TN.
Infrared identification of Organic Unknowns - Includes a brief description of the theory, a step-by-step guide to peak assignment and some problems.
Infrared Spectroscopy - Includes information on the principles, absorption peaks for organic molecule functional groups and sample preparation methods, as part of the general program at Worcester Polytechnic Institute, Massachusetts.
Infrared Spectroscopy and Greenhouse Gases - Introduction and overview, maintained at the Department of Chemistry, Widener University, Chester, Pennsylvania.
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Infrared Spectroscopy of Overtones and Combination Bands - [PDF] A paper on the analysis and mechanisms in these bands.
IR Spectroscopy Tutorial - Contains an introduction to infrared spectroscopy as well as sample infrared spectra.
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NIR Publications - Resources, including books, bimonthly newsletter, and Journal of Near Infrared Spectroscopy offered in electronic, CD-ROM and hardcopy. Includes abstracts and a search facility, with full text available for subscribers, as well as instructions for authors.
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