Absorption Band
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Absorption Band
A range of wavelengths (or frequencies) in the
electromagnetic spectrum within
which radiant energy is absorbed by a substance.
See
absorption spectrum.
When the absorbing substance is a polyatomic gas, an absorption
band actually is composed of a group of discrete absorption lines
which appear to overlap. Each line is associated with a particular
mode of vibration or rotation induced in a gas molecule by the
incident radiation.
The absorption bands of oxygen and ozone are
often referred to in the literature of atmospheric physics.
The
important bands for oxygen are: (a) the Hopfield bands, very strong,
between about 670 and 1000 angstroms in the ultraviolet; (b) a
diffuse system between 1019 and 1300 angstroms; (c) the Schumann-Runge
continuum, very strong, between 1350 and 1760 angstroms; (d) the
Schumann-Runge bands between 1760 and 1926 angstroms; (e) the
Herzberg bands between 2400 and 2600 angstroms; (f) the atmospheric
bands between 5380 and 7710 angstroms in the visible spectrum;
and (g) a system in the infrared at about 1 micron.
The important
bands for ozone are: (a) the Hartley bands between 2000 and 3000
angstroms in the ultraviolet, with a very intense maximum absorption
at 2550 angstroms; (b) the Huggins bands, weak absorption
between 3200 and 3600 angstroms; (c) the Chappius bands, a weak
diffuse system between 4500 and 6500 angstroms in the visible
spectrum; and (d) the infrared bands centered at 4.7, 9.6 and
14.1 microns, the latter being the most intense.
[edit] References
This article is based on NASA's Dictionary of Technical Terms for Aerospace Use
