Molecule

A molecule is the smallest particle of a pure chemical substance that still retains its chemical composition and properties. The science of molecules is called molecular chemistry or molecular physics, depending on the particular aspect of focus. Molecular chemistry is concerned with the laws governing the interaction between molecules that results in the formation and breakage of chemical bonds, while molecular physics is concerned with the laws governing their structure and properties. In practice, however, this distinction is rather vague.

Molecular spectroscopy

:see main article spectroscopy

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Molecular spectroscopy is the study of the response (spectrum) of a molecule to a signal characterized by its tunable frequency (or, according to Planck formula, its energy). This signal is usually an electromagnetic wave or a beam of electrons, but new molecular spectroscopies are under development like the positron spectroscopy. The molecular response can be the absorption of the signal (absorption spectroscopy), the emission of another signal (emission spectroscopy), its fragmentation or a change of its chemical nature.

Related Topics:
Spectrum - Frequency - Planck formula - Electromagnetic wave - Electron - Positron - Absorption spectroscopy - Emission spectroscopy

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Spectroscopy is recognized as the most powerful tool in the investigation of the microscopic properties of molecules, and, in particular, their energy levels. Nowadays, in order to extract the maximum microscopic information from the experimental results, spectroscopical studies are very often coupled with computational chemical investigations. The theoretical background of spectroscopy is the scattering theory.

Related Topics:
Energy level - Computational chemical - Scattering theory

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