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Spectroscopy

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Spectroscopy is the study of the interaction between matter and electromagnetic radiation as a function of the wavelength or frequency of the radiation. In simpler terms, spectroscopy is the precise study of color as generalized from visible light to all bands of the electromagnetic spectrum; indeed, historically, spectroscopy originated as the study of the wavelength dependence of the absorption by gas phase matter of visible light dispersed by a prism. Matter waves and acoustic waves can also be considered forms of radiative energy, and recently gravitational waves have been associated with a spectral signature in the context of the Laser Interferometer Gravitational-Wave Observatory (LIGO). Spectroscopy, primarily in the electromagnetic spectrum, is a fundamental exploratory tool in the fields of physics, chemistry, and astronomy, allowing the composition, physical structure and electronic structure of matter to be investigated at the atomic, molecular and macro scale, and over as...
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Other types

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This section is in list format, but may read better as prose . You can help by converting this section, if appropriate. Editing help is available. ( April 2016 ) Other types of spectroscopy are distinguished by specific applications or implementations: Acoustic resonance spectroscopy is based on sound waves primarily in the audible and ultrasonic regions. Auger electron spectroscopy is a method used to study surfaces of materials on a micro-scale. It is often used in connection with electron microscopy. Cavity ring-down spectroscopy Circular Dichroism spectroscopy Coherent anti-Stokes Raman spectroscopy is a recent technique that has high sensitivity and powerful applications for in vivo spectroscopy and imaging. Cold vapour atomic fluorescence spectroscopy Correlation spectroscopy encompasses several types of two-dimensional NMR spectroscopy. Deep-level transient spectroscopy measures concentration and analyzes parameters of electrically active defects in semiconducting mat...
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Theory

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One of the central concepts in spectroscopy is a resonance and its corresponding resonant frequency. Resonances were first characterized in mechanical systems such as pendulums. Mechanical systems that vibrate or oscillate will experience large amplitude oscillations when they are driven at their resonant frequency. A plot of amplitude vs. excitation frequency will have a peak centered at the resonance frequency. This plot is one type of spectrum, with the peak often referred to as a spectral line, and most spectral lines have a similar appearance. In quantum mechanical systems, the analogous resonance is a coupling of two quantum mechanical stationary states of one system, such as an atom, via an oscillatory source of energy such as a photon. The coupling of the two states is strongest when the energy of the source matches the energy difference between the two states. The energy ( E ) {\displaystyle (E)} of a photon is related to its frequency ( ν ) {\displaystyle ...
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