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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 ...

Spectroscopy is a sufficiently broad field that many sub-disciplines exist, each with numerous implementations of specific spectroscopic techniques. The various implementations and techniques can be classified in several ways. Type of radiative energy edit The types of spectroscopy are distinguished by the type of radiative energy involved in the interaction. In many applications, the spectrum is determined by measuring changes in the intensity or frequency of this energy. The types of radiative energy studied include: Electromagnetic radiation was the first source of energy used for spectroscopic studies. Techniques that employ electromagnetic radiation are typically classified by the wavelength region of the spectrum and include microwave, terahertz, infrared, near-infrared, ultraviolet-visible, x-ray, and gamma spectroscopy. Particles, because of their de Broglie waves, can also be a source of radiative energy. Both electron and neutron spectroscopy are commonly used. For a particl...

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...

Cure monitoring of composites using optical fibers. Estimate weathered wood exposure times using near infrared spectroscopy. Measurement of different compounds in food samples by absorption spectroscopy both in visible and infrared spectrum. Measurement of toxic compounds in blood samples Non-destructive elemental analysis by X-ray fluorescence. Electronic structure research with various spectroscopes.

The history of spectroscopy began with Isaac Newton's optics experiments (1666–1672). According to Andrew Fraknoi and David Morrison, "In 1672, in the first paper that he submitted to the Royal Society, Isaac Newton described an experiment in which he permitted sunlight to pass through a small hole and then through a prism. Newton found that sunlight, which looks white to us, is actually made up of a mixture of all the colors of the rainbow." Newton applied the word "spectrum" to describe the rainbow of colors that combine to form white light and that are revealed when the white light is passed through a prism. Fraknoi and Morrison state that "In 1802, William Hyde Wollaston built an improved spectrometer that included a lens to focus the Sun's spectrum on a screen. Upon use, Wollaston realized that the colors were not spread uniformly, but instead had missing patches of colors, which appeared as dark bands in the spectrum." During the early 1800s,...