Editing Spectroscopy (section)

== Introduction ==
Spectroscopy is a branch of science concerned with the [[spectrum|spectra]] of [[electromagnetic radiation]] as a function of its wavelength or frequency measured by [[spectrograph]]ic equipment, and other techniques, in order to obtain information concerning the structure and properties of matter.<ref>{{Cite book |url=https://books.google.com/books?id=U5MdAQAAIAAJ |title=The Oxford American College Dictionary |date=2002 |publisher=G.P. Putnam's Sons |isbn=9780399144158 |oclc=48965005}}</ref> Spectral measurement devices are referred to as [[spectrometers]], [[spectrophotometers]], [[spectrograph]]s or [[spectral analyzer]]s. Most spectroscopic analysis in the laboratory starts with a sample to be analyzed, then a light source is chosen from any desired range of the light spectrum, then the light goes through the sample to a dispersion array (diffraction grating instrument) and captured by a [[photodiode]]. For astronomical purposes, the telescope must be equipped with the light dispersion device. There are various versions of this basic setup that may be employed.

Spectroscopy began with [[Isaac Newton]] splitting light with a prism; a key moment in the development of modern [[optics]].<ref>"[https://www.aaas.org/isaac-newton-and-problem-color Isaac Newton and the problem of color]", Steven A. Edwards, AAAS.</ref> Therefore, it was originally the study of visible light that we call [[color]] that later under the studies of [[James Clerk Maxwell]] came to include the entire [[electromagnetic spectrum]].<ref>{{cite web|url=http://www.kcl.ac.uk/newsevents/news/newsrecords/2011/04Apr/JamesClerkMaxwell.aspx |title=1861: James Clerk Maxwell's greatest year |date=18 April 2011 |publisher=King's College London |access-date=28 March 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130622095747/http://www.kcl.ac.uk/newsevents/news/newsrecords/2011/04Apr/JamesClerkMaxwell.aspx |archive-date=22 June 2013 }}</ref> Although color is involved in spectroscopy, it is not equated with the color of elements or objects that involve the absorption and reflection of certain electromagnetic waves to give objects a sense of color to our eyes. Rather spectroscopy involves the splitting of light by a prism, diffraction grating, or similar instrument, to give off a particular discrete line pattern called a "spectrum" unique to each different type of element. Most elements are first put into a gaseous phase to allow the spectra to be examined although today other methods can be used on different phases. Each element that is diffracted by a prism-like instrument displays either an absorption spectrum or an emission spectrum depending upon whether the element is being cooled or heated.<ref name="auto">PASCO, "[https://www.pasco.com/products/guides/what-is-spectroscopy What is Spectroscopy?]"</ref>

Until recently all spectroscopy involved the study of line spectra and most spectroscopy still does.<ref>Sutton, M. A. "[http://www.jstor.org/stable/4025175 Sir John Herschel and the Development of Spectroscopy in Britain]". The British Journal for the History of Science, vol. 7, no. 1, [Cambridge University Press, The British Society for the History of Science], 1974, pp. 42–60.</ref> Vibrational spectroscopy is the branch of spectroscopy that studies the spectra.<ref>Lazić, Dejan. "Introduction to Raman Microscopy/Spectroscopy". Application of Molecular Methods and Raman Microscopy/Spectroscopy in Agricultural Sciences and Food Technology, edited by Dejan Lazić et al., Ubiquity Press, 2019, pp. 143–50, http://www.jstor.org/stable/j.ctvmd85qp.12.
</ref> However, the latest developments in spectroscopy can sometimes dispense with the dispersion technique. In biochemical spectroscopy, information can be gathered about biological tissue by absorption and light scattering techniques. Light scattering spectroscopy is a type of reflectance spectroscopy that determines tissue structures by examining elastic scattering.<ref name="link.aps.org">{{Cite journal |last1=Perelman |first1=L. T. |last2=Backman |first2=V. |last3=Wallace |first3=M. |last4=Zonios |first4=G. |last5=Manoharan |first5=R. |last6=Nusrat |first6=A. |last7=Shields |first7=S. |last8=Seiler |first8=M. |last9=Lima |first9=C. |last10=Hamano |first10=T. |last11=Itzkan |first11=I. |last12=Van Dam |first12=J. |last13=Crawford |first13=J. M. |last14=Feld |first14=M. S. |date=1998-01-19 |title=Observation of Periodic Fine Structure in Reflectance from Biological Tissue: A New Technique for Measuring Nuclear Size Distribution |url=https://link.aps.org/doi/10.1103/PhysRevLett.80.627 |journal=Physical Review Letters |volume=80 |issue=3 |pages=627–630 |doi=10.1103/PhysRevLett.80.627|bibcode=1998PhRvL..80..627P }}</ref> In such a case, it is the tissue that acts as a diffraction or dispersion mechanism.

Spectroscopic studies were central to the development of [[quantum mechanics]], because the first useful atomic models described the spectra of hydrogen, which include the [[Bohr model]], the [[Schrödinger equation]], and [[Matrix mechanics]], all of which can produce the spectral lines of [[hydrogen]], therefore providing the basis for discrete quantum jumps to match the discrete hydrogen spectrum. Also, [[Max Planck]]'s explanation of [[blackbody radiation]] involved spectroscopy because he was comparing the wavelength of light using a photometer to the temperature of a [[Black Body]].<ref>Kumar, Manjit. Quantum: Einstein, Bohr, and the great debate about the nature of reality / Manjit Kumar.—1st American ed., 2008. Chap.1.</ref> Spectroscopy is used in [[physical chemistry|physical]] and [[analytical chemistry]] because [[atoms]] and [[molecules]] have unique spectra. As a result, these spectra can be used to detect, identify and quantify information about the atoms and molecules. Spectroscopy is also used in [[astronomical spectroscopy|astronomy]] and [[remote sensing]] on Earth. Most research [[telescopes]] have spectrographs. The measured spectra are used to determine the chemical composition and [[physical property|physical properties]] of [[astronomical objects]] (such as their [[temperature]], density of elements in a star, [[velocity]], [[black holes]] and more).<ref>{{cite web |title=Spectra and What They Can Tell Us |publisher=NASA Goddard Space Flight Center |url=https://imagine.gsfc.nasa.gov/science/toolbox/spectra1.html |date=August 2013 |website=Imagine the Universe! }}</ref> An important use for spectroscopy is in biochemistry. Molecular samples may be analyzed for species identification and energy content.<ref>{{cite web |title=Basic Spectroscopy |first1=Santi |last1=Nonell|first2=Cristiano |last2=Viappiani |url=http://photobiology.info/Nonell_Viappiani.html |website=Photobiological Sciences Online }}</ref>