Spectroscopy is the use of the absorption, emission, or scattering of
electromagnetic radiation by matter to qualitatively or quantitatively
study the matter or to study physical processes. The matter can be atoms,
molecules, atomic or molecular ions, or solids. The interaction of
radiation with matter can cause redirection of the radiation and/or
transitions between the energy levels of the atoms or molecules.
- Absorption: A transition from a lower
level to a higher level with transfer of energy from the radiation
field to an absorber, atom, molecule, or solid.
- Emission: A transition from a higher
level to a lower level with transfer of energy from the emitter to the
radiation field. If no radiation is emitted, the transition from
higher to lower energy levels is called nonradiative decay.
- Scattering: Redirection of light due to
its interaction with matter. Scattering might or might not occur with
a transfer of energy, i.e., the scattered radiation might or might not
have a slightly different wavelength compared to the light incident on
the sample.
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