Theory of the Fireball

causes of absorption are the molecular bands of
N (first positive) from about 1 to 2-1/4 ev
2
N: (first negative) " 2-1/2 to 3-3/4 ev
NO (e bands)
11
" 2-1/2 to 6 ev
and the continuous absorption due to 0- photodetachment from about 1-1/2
ev up. The N2 second positive, and 0 Schumann-Runge, although they con-
2
tribute, are . .
usually weaker than the combination of N+ first negative and
2
NO and cover the same region of the spectrum (or less) 0- photodetach-
ment is mostly important at the higher density, p/p = 1.
0
There is comonly a %Window" of low absorption below 1 ev, between
free-free absorption and N2(lf), and another at about 2-1/2 ev, between
N2 and the other bands (Table IV) . The latter window is filled in by 0-
photodetachment. At higher temperature, such as 12,000°, the photoelectric
effect on N and 0 becomes important and the.molecular bands almost dis-
appear; the absorption coefficient is then almost uniform over the entire
spectrum.
The table by Meyerott et al. should be consulted for details. Apart
from the free-free transitions, this table seems to be in error on the
N2( 1') absorption at 8000°, which should be increased by a factor of 4.
With these corrections, Table IV gives the absorption coefficients at
8000' for a few frequencies and densities, mentioning in each case only
the most important species of absorbers. For p/po = 0.1 and 0.01, the
contribution of NO and O2 in the wave length region considered is negli-
gible. The windows at 1 and above 2 ev are noticeable in the table; beyond
3 ev there is a rapid increase in absorption.
35
J
L. -~