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Infrared spectroscopy (IR spectroscopy or vibrational spectroscopy) is the measurement of the interaction of infrared radiation with matter by absorption, emission, or reflection. It is used to study and identify chemical substances or functional groups in solid, liquid, or gaseous forms. It can be used to characterize new materials or identify ...
A molecular vibration is a periodic motion of the atoms of a molecule relative to each other, such that the center of mass of the molecule remains unchanged. The typical vibrational frequencies range from less than 10 13 Hz to approximately 10 14 Hz, corresponding to wavenumbers of approximately 300 to 3000 cm −1 and wavelengths of approximately 30 to 3 μm.
An infrared spectroscopy correlation table (or table of infrared absorption frequencies) is a list of absorption peaks and frequencies, typically reported in wavenumber, for common types of molecular bonds and functional groups.
The infrared spectrum of liquid water is dominated by the intense absorption due to the fundamental O-H stretching vibrations. Because of the high intensity, very short path lengths, usually less than 50 μm, are needed to record the spectra of aqueous solutions.
In CO 2, the bending vibration ν 2 (667 cm −1) has symmetry Π u.The first excited state of ν 2 is denoted 01 1 0 (no excitation in the ν 1 mode (symmetric stretch), one quantum of excitation in the ν 2 bending mode with angular momentum about the molecular axis equal to ±1, no excitation in the ν 3 mode (asymmetric stretch)) and clearly transforms according to the irreducible ...
A vibration will be active in the IR if there is a change in the dipole moment of the molecule and if it has the same symmetry as one of the x, y, z coordinates. To determine which modes are IR active, the irreducible representation corresponding to x, y, and z are checked with the reducible representation of Γ vib. [4]
Simulated vibration-rotation line spectrum of carbon monoxide, 12 C 16 O. The P-branch is to the left of the gap near 2140 cm −1, the R-branch on the right. [note 2] Schematic ro-vibrational energy level diagram for a linear molecule. Diatomic molecules with the general formula AB have one normal mode of vibration involving stretching of the ...
Researchers employ various organic and biochemical methods to introduce small vibrational probes into molecular systems into a variety of chemicals, proteins, nucleic acids, etc. [4] These probes, labeled with infrared (IR) markers, were subject to spectroscopic investigations to obtain quantitative insights into various features of chemical ...