Infrared spectroscopy

infraredIR spectroscopyinfrared spectrometervibrational spectroscopyIRinfrared spectrumIR spectrumIR spectraInfrared spectrainfrared (IR) spectroscopy
Infrared spectroscopy (IR spectroscopy or vibrational spectroscopy) involves the interaction of infrared radiation with matter.wikipedia
559 Related Articles

Infrared

IRnear-infraredinfra-red
Infrared spectroscopy (IR spectroscopy or vibrational spectroscopy) involves the interaction of infrared radiation with matter.
Infrared radiation is emitted or absorbed by molecules when they change their rotational-vibrational movements.

Absorption spectroscopy

absorption spectrumabsorption spectraabsorption
It covers a range of techniques, mostly based on absorption spectroscopy.
Infrared and ultraviolet-visible spectroscopy are particularly common in analytical applications.

Rotational–vibrational spectroscopy

Rotational-vibrational spectroscopyvibrational spectroscopybond stretch
The mid-infrared, approximately 4000–400 cm −1 (2.5–25 μm) may be used to study the fundamental vibrations and associated rotational-vibrational structure.
Rotational–vibrational spectroscopy is a branch of molecular spectroscopy concerned with infrared and Raman spectra of molecules in the gas phase.

Fourier-transform infrared spectroscopy

FTIRFourier transform infrared spectroscopyFT-IR
A common laboratory instrument that uses this technique is a Fourier transform infrared (FTIR) spectrometer.
The first low-cost spectrophotometer capable of recording an infrared spectrum was the Perkin-Elmer Infracord produced in 1957.

Near-infrared spectroscopy

near infrared spectroscopyNIRSnear-infrared
The infrared portion of the electromagnetic spectrum is usually divided into three regions; the near-, mid- and far- infrared, named for their relation to the visible spectrum.
One advantage is that NIR can typically penetrate much further into a sample than mid infrared radiation.

Molecular vibration

vibrationalvibrational stateVibrational transition
The higher-energy near-IR, approximately 14000–4000 cm −1 (0.7–2.5 μm wavelength) can excite overtone or harmonic molecular vibrations.
The most direct way is through infrared spectroscopy, as vibrational transitions typically require an amount of energy that corresponds to the infrared region of the spectrum.

Molecular geometry

Bond anglegeometrymolecular structure
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 associated with the normal modes corresponding to the molecular electronic ground state potential energy surface.
IR, microwave and Raman spectroscopy can give information about the molecule geometry from the details of the vibrational and rotational absorbance detected by these techniques.

Overtone band

overtoneovertones
In some cases, overtone bands are observed.
In vibrational spectroscopy, an overtone band is the spectral band that occurs in a vibrational spectrum of a molecule when the molecule makes a transition from the ground state (v=0) to the second excited state (v=2), where v is the vibrational quantum number (a non-negative integer) obtained from solving the Schrödinger equation for the molecule.

Nujol

One common method is to crush the sample with an oily mulling agent (usually mineral oil Nujol).
Nujol is a brand of mineral oil by Plough Inc., cas number 8012-95-1, and density 0.838 g/mL at 25 °C, used in infrared spectroscopy.

Rotational spectroscopy

microwave spectroscopyrotationalrotational spectra
The far-infrared, approximately 400–10 cm −1 (25–1000 μm), lying adjacent to the microwave region, has low energy and may be used for rotational spectroscopy.
Historically, the theory of rotational energy levels was developed to account for observations of vibration-rotation spectra of gases in infrared spectroscopy, which was used before microwave spectroscopy had become practical.

Attenuated total reflectance

ATRATR-cellATR-IR
A useful way of analyzing solid samples without the need for cutting samples uses ATR or attenuated total reflectance spectroscopy.
Attenuated total reflection (ATR) is a sampling technique used in conjunction with infrared spectroscopy which enables samples to be examined directly in the solid or liquid state without further preparation.

Chemical structure

structureconformationstructurally
Infrared spectroscopy exploits the fact that molecules absorb frequencies that are characteristic of their structure.
Techniques such as absorption spectroscopy and the vibrational spectroscopies, infrared and Raman, provide, respectively, important supporting information about the numbers and adjacencies of multiple bonds, and about the types of functional groups (whose internal bonding gives vibrational signatures); further inferential studies that give insight into the contributing electronic structure of molecules include cyclic voltammetry and X-ray photoelectron spectroscopy.

Normal mode

modesnormal modesmode
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 associated with the normal modes corresponding to the molecular electronic ground state potential energy surface.

AFM-IR

atomic force microscope based infrared spectroscopy (AFM-IR)atomic force microscope based infrared spectroscopy (AFM-IR).Atomic force microscopy based infrared spectroscopy (AFM-IR)
AFM-IR (atomic force microscope infrared-spectroscopy) is one of a family of techniques that are derived from a combination of two parent instrumental techniques; infrared spectroscopy and scanning probe microscopy (SPM).

Organic compound

syntheticorganicorganic compounds
The atoms in a CH 2 X 2 group, commonly found in organic compounds and where X can represent any other atom, can vibrate in nine different ways.
The main tools are proton and carbon-13 NMR spectroscopy, IR Spectroscopy, Mass spectrometry, UV/Vis Spectroscopy and X-ray crystallography.

Multipass spectroscopic absorption cells

White cellsHerriottmulti-pass cells
Sample gas concentrations well below ppm can be measured with a White's cell in which the infrared light is guided with mirrors to travel through the gas.

Metal carbonyl

carbonylInfrared spectroscopy of metal carbonylsBridging carbonyl
Infrared spectroscopy is a sensitive probe for the presence of bridging carbonyl ligands.

Electron energy loss spectroscopy

EELSelectron energy loss (EEL)electron energy loss spectrometer
Ultrahigh energy resolution electron energy loss spectroscopy (EELS) has recently emerged as a new technique for performing infrared spectroscopy in the transmission electron microscope (TEM).
Recent instrumental developments opened up the ultra-low energy loss part of the EELS spectrum, enabling vibrational spectroscopy in the TEM.

Vibrational spectroscopy of linear molecules

Vibrational spectra
To determine the vibrational spectroscopy of linear molecules, the rotation and vibration of linear molecules are taken into account to predict which vibrational (normal) modes are active in the infrared spectrum and the Raman spectrum.

Raman spectroscopy

RamanRaman spectrumRaman spectra
If the molecule is symmetrical, e.g. N 2, the band is not observed in the IR spectrum, but only in the Raman spectrum.
Infrared spectroscopy typically yields similar, complementary, information.

Microtome

ultramicrotomemicrotomyparaffin block
The final method is to use microtomy to cut a thin (20–100 μm) film from a solid sample.

Potassium bromide

KBrbromidebromide of potassium
Liquid samples can be sandwiched between two plates of a salt (commonly sodium chloride, or common salt, although a number of other salts such as potassium bromide or calcium fluoride are also used).
In infrared spectroscopy, samples are analyzed by grinding with powdered potassium bromide and pressing into a disc.

Photoacoustic spectroscopy

photoacoustic
In photoacoustic spectroscopy the need for sample treatment is minimal.
One of the important capabilities of using FTIR photoacoustic spectroscopy has been the ability to evaluate samples in their in situ state by infrared spectroscopy, which can be used to detect and quantify chemical functional groups and thus chemical substances.

Infrared spectroscopy correlation table

typical frequencies of molecular motions
In physical and analytical chemistry, infrared spectroscopy (IR spectroscopy) is a technique used to identify chemical compounds based on the way infrared radiation is absorbed by the compound.

Photothermal microspectroscopy

PTTF
Photothermal microspectroscopy (PTMS), alternatively known as photothermal temperature fluctuation (PTTF), is derived from two parent instrumental techniques: infrared spectroscopy and atomic force microscopy (AFM).