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.
References
This article is based on NASA's Dictionary of Technical Terms for Aerospace Use
