Infrared 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 and verify known and unknown samples. The method or technique of infrared spectroscopy is conducted with an instrument called an infrared spectrometer which produces an infrared spectrum. An IR spectrum can be visualized in a graph of infrared light absorbance on the vertical axis vs. frequency, wavenumber or wavelength on the horizontal axis. Typical units of wavenumber used in IR spectra are reciprocal centimeters, with the symbol cm−1. Units of IR wavelength are commonly given in micrometers, symbol μm, which are related to the wavenumber in a reciprocal way. A common laboratory instrument that uses this technique is a Fourier transform infrared (FTIR) spectrometer. Two-dimensional IR is also possible as discussed below.
A molecule is a group of two or more atoms that are held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemistry, and biochemistry, the distinction from ions is dropped and molecule is often used when referring to polyatomic ions.
Spectroscopy is the field of study that measures and interprets electromagnetic spectra. In narrower contexts, spectroscopy is the precise study of color as generalized from visible light to all bands of the electromagnetic spectrum.
Theoretical chemistry is the branch of chemistry which develops theoretical generalizations that are part of the theoretical arsenal of modern chemistry: for example, the concepts of chemical bonding, chemical reaction, valence, the surface of potential energy, molecular orbitals, orbital interactions, and molecule activation.
Absorption spectroscopy is spectroscopy that involves techniques that measure the absorption of electromagnetic radiation, as a function of frequency or wavelength, due to its interaction with a sample. The sample absorbs energy, i.e., photons, from the radiating field. The intensity of the absorption varies as a function of frequency, and this variation is the absorption spectrum. Absorption spectroscopy is performed across the electromagnetic spectrum.
A chemical structure of a molecule is a spatial arrangement of its atoms and their chemical bonds. Its determination includes a chemist's specifying the molecular geometry and, when feasible and necessary, the electronic structure of the target molecule or other solid. Molecular geometry refers to the spatial arrangement of atoms in a molecule and the chemical bonds that hold the atoms together and can be represented using structural formulae and by molecular models; complete electronic structure descriptions include specifying the occupation of a molecule's molecular orbitals. Structure determination can be applied to a range of targets from very simple molecules to very complex ones.
Rotational spectroscopy is concerned with the measurement of the energies of transitions between quantized rotational states of molecules in the gas phase. The rotational spectrum of polar molecules can be measured in absorption or emission by microwave spectroscopy or by far infrared spectroscopy. The rotational spectra of non-polar molecules cannot be observed by those methods, but can be observed and measured by Raman spectroscopy. Rotational spectroscopy is sometimes referred to as pure rotational spectroscopy to distinguish it from rotational-vibrational spectroscopy where changes in rotational energy occur together with changes in vibrational energy, and also from ro-vibronic spectroscopy where rotational, vibrational and electronic energy changes occur simultaneously.
Molecular geometry is the three-dimensional arrangement of the atoms that constitute a molecule. It includes the general shape of the molecule as well as bond lengths, bond angles, torsional angles and any other geometrical parameters that determine the position of each atom.
Two-Dimensional Nuclear Magnetic Resonance is an advanced spectroscopic technique that builds upon the capabilities of one-dimensional (1D) NMR by incorporating an additional frequency dimension. This extension allows for a more comprehensive analysis of molecular structures. In 2D NMR, signals are distributed across two frequency axes, providing improved resolution and separation of overlapping peaks, particularly beneficial for studying complex molecules. This technique identifies correlations between different nuclei within a molecule, facilitating the determination of connectivity, spatial proximity, and dynamic interactions.
Characterization, when used in materials science, refers to the broad and general process by which a material's structure and properties are probed and measured. It is a fundamental process in the field of materials science, without which no scientific understanding of engineering materials could be ascertained. The scope of the term often differs; some definitions limit the term's use to techniques which study the microscopic structure and properties of materials, while others use the term to refer to any materials analysis process including macroscopic techniques such as mechanical testing, thermal analysis and density calculation. The scale of the structures observed in materials characterization ranges from angstroms, such as in the imaging of individual atoms and chemical bonds, up to centimeters, such as in the imaging of coarse grain structures in metals.
Applied spectroscopy is the application of various spectroscopic methods for the detection and identification of different elements or compounds to solve problems in fields like forensics, medicine, the oil industry, atmospheric chemistry, and pharmacology.
Herbert Sander Gutowsky was an American chemist who was a professor of chemistry at the University of Illinois Urbana-Champaign. Gutowsky was the first to apply nuclear magnetic resonance (NMR) methods to the field of chemistry. He used nuclear magnetic resonance spectroscopy to determine the structure of molecules. His pioneering work developed experimental control of NMR as a scientific instrument, connected experimental observations with theoretical models, and made NMR one of the most effective analytical tools for analysis of molecular structure and dynamics in liquids, solids, and gases, used in chemical and medical research, His work was relevant to the solving of problems in chemistry, biochemistry, and materials science, and has influenced many of the subfields of more recent NMR spectroscopy.
Michael L. Gross is Professor of Chemistry, Medicine, and Immunology, at Washington University in St. Louis. He was formerly Professor of Chemistry at the University of Nebraska-Lincoln from 1968–1994. He is recognized for his contributions to the field of mass spectrometry and ion chemistry. He is credited with the discovery of distonic ions, chemical species containing a radical and an ionic site on different atoms of the same molecule.
Instrumental analysis is a field of analytical chemistry that investigates analytes using scientific instruments.
Nitrosyl-O-hydroxide is an isomer of nitrous acid, which has been experimentally observed in the gas phase. HOON contains the longest oxygen-oxygen bond thus far observed in any known molecule, measured to be 1.9149 angstroms. There had been speculation about the existence of this molecule, and ab initio calculations have suggested that it might have a stable chemically bonded structure.
Calcium monohydride is a molecule composed of calcium and hydrogen with formula CaH. It can be found in stars as a gas formed when calcium atoms are present with hydrogen atoms.
Argon compounds, the chemical compounds that contain the element argon, are rarely encountered due to the inertness of the argon atom. However, compounds of argon have been detected in inert gas matrix isolation, cold gases, and plasmas, and molecular ions containing argon have been made and also detected in space. One solid interstitial compound of argon, Ar1C60 is stable at room temperature. Ar1C60 was discovered by the CSIRO.
Structural chemistry is a part of chemistry and deals with spatial structures of molecules and solids. For structure elucidation a range of different methods is used. One has to distinguish between methods that elucidate solely the connectivity between atoms (constitution) and such that provide precise three dimensional information such as atom coordinates, bond lengths and angles and torsional angles.
Wolfgang Stahl was a German spectroscopist. He was a professor at the RWTH Aachen University.
In physics, monochromatic radiation is electromagnetic radiation with a single constant frequency or wavelength. When that frequency is part of the visible spectrum the term monochromatic light is often used. Monochromatic light is perceived by the human eye as a spectral color.
