Emission spectroscopy

From Wikipedia, the free encyclopedia

Emission spectroscopy is a spectroscopic technique which examines the discrete photon emissions as electromagnetic spectra radiated by some given element. The element first absorbs energy elevating electrons to higher energies, then radiates this energy as characteristic emissions (photons of a particular wavelength) as the electrons drop back to lower energy levels. This excitation energy can be from a variety of sources, including collision (either due to high temperatures or otherwise), chemical reactions, and light. Spectrofluorimetry in chemistry is an example of emission spectroscopy.

Emission spectroscopy requires the emission source to be analyzed, a spectrometer and a detector. Spectrometers or monochromators are devices which use a diffraction grating to separate the incoming light according to wavelength. A small range of this separated spectrum is then collected by a detector, usually a charge coupled device (CCD) camera.

Emission spectrum of an element consists of several emission lines, each corresponding to a specific electron transition.

Each of these lines, however is not perfectly monochromatic, meaning it does not have a single wavelength. It has a finite spread, which is called as the shape of the spectral line or spectral line broadening.