Spectroscopy << spehk TRAHS kuh pee >> is the scientific study of how matter interacts with light and certain other forms of energy. In spectroscopy, scientists study the radiation given off, absorbed, or scattered by a material to learn more about the material’s composition or structure. For example, a scientist might study the light given off by a star to determine the chemical elements present in the star. Many kinds of spectroscopy make use of ultraviolet (UV) light, visible light, X rays, and other forms of electromagnetic radiation. Other kinds of spectroscopy use beams of charged particles or even sound.
The study of spectroscopy began with the work of Sir Isaac Newton in the late 1600’s. Newton used a glass prism to separate sunlight into a rainbow of colors, which he called a spectrum. Today, the word spectrum (plural, spectra) can be used to mean a plot showing how much electromagnetic radiation a substance gives off, absorbs, or scatters at each wavelength. The study of such spectra gives spectroscopy its name.
One important type of spectroscopy is called nuclear magnetic resonance (NMR) spectroscopy. It uses a magnetic field to study radio wave spectral differences in the nuclei (cores) of atoms. By analyzing these differences, scientists can learn how many atoms of a particular kind are present in a particular molecule and what kind of atoms are bonded to them. Magnetic resonance imaging (MRI) uses a similar spectroscopic technique to obtain images of tissues inside the body.
Infrared (IR) spectroscopy uses infrared rays to study the stretching and bending of chemical bonds. The energy needed to bend and stretch a bond depends on what atoms make up the bond and how many electrons they share. By studying the infrared spectrum of a molecule, scientists can therefore learn what kinds of chemical bonds are present in the molecule.
Researchers can use visible, UV, and X-ray spectroscopy to study what happens when electrons absorb energy and become excited. Another type of X-ray spectroscopy can be used to produce an actual image of large molecules such as proteins.
See also Light (The spectrum of light sources) ; Spectrometer ; Spectrum .
