Molecular beams

Article By:

Bayfield, James E. Department of Physics, University of Pittsburgh, Pittsburgh, Pennsylvania.

Last reviewed:January 2020

DOI:https://doi.org/10.1036/1097-8542.430200

Utilization of well-directed streams of atoms or molecules in vacuum. This is a cornerstone technique in the investigation of molecular structure and interactions. Molecular beams are usually formed at sufficiently low particle density for the interaction of one beam molecule with another to be negligible. This ensemble of truly isolated molecules is available for the spectroscopic study of molecular energy levels using photon probes from the radio-frequency to optical portions of the electromagnetic spectrum. Some of the best-determined fundamental knowledge of physics comes from spectroscopic molecular-beam experiments. Beyond this, beams can be applied as probes of the multifaceted nature of gases, plasmas, surfaces, and even the structure of solids. An application intermediate in complexity is the study of molecular interactions determining the properties of plasma and electric discharge devices, the nature of the upper atmosphere, and some aspects of the cooler astrophysical regions. See also: Scattering experiments (atoms and molecules)

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