electronic absorption band. There are vibrational or rotational absorption bands
when the electronic energy is not changed. Spectra are called also electronic,
vibrational or rotational. The complicated character of molecule total energy
variations is responsible for complicated structure of molecule spectrum.
The spectral line broadening is observed as it will be considered below. The
contour of spectral line f
ðiÞ n; n
ðiÞ
0
describes this broadening.
3.2 Infrared Spectral Range
Only carbon dioxide is considered here as atmospheric gaseous component because
of invariable content. The expression for calculating the monochromatic absorption
coefficient k n might be written as the sum over all lines within the spectral
ranges Dn:
k n ¼
X N
i¼1
k n
ðiÞ
;
(3.1)
E vibr
DE rot
DE el
E el 2
E vibr
DE el
E el 1
n rot
n vibr+rot n el+vibr+rot
n
Fig. 3.1 Energy levels of the molecule
3.2 Infrared Spectral Range
29