.
lines will appear as such if the spectrograph is of sufficiently high resolving power. Sometimes
rotational lines are so close together that they are not inherently resolved because of the finite
width of the individual lines involved. As is well known, line broadening can be attributed not
only to the nature of the molecule but also to external causes such as temperature, pressure,
and external electric or magnetic ftelds.
,
assoc
and a
msity of a spectral line depends on both the population of the initial energy level
*
jwith the optical transition and on the transition probability. This holds for emission
on, the initial state being of higher energy in emission and of lower energy in
absorption.
In an ideal case, two intensity distributions can be obtained from molecular spectra—that
of the intensities of the rotational lines in a v-v, or vibration band, and that of sums of these
rotational line intensities taken for many v-v transitions. The first would give an effective
rotational temperature and the second an effective vibrational temperature. These temperatures have little meaning if equilibrium conditions do not exist. They alao lose significance if
the intensities or the sums of intensities represent averages taken over too much time or space.
This is the situation in nearly all the experiments deacribed in the present report. Conse-
quently, intensity distributions are given which cannot always be interpreted in terms of temperature.
e
.
However, by using intensity distributions of certain oxygen band systems, approximate
values of the rotational temperatures were calculated for three of the shots in two ways:
1. Ina particular band, the line of maximum intensity was found, and the corresponding
total angular momentum ofthe initial quantum state (J value) was noted: An approximate
theoretical expression for line intensity in terms of J and T (temperature) was maximized so
that by substitution of the J value of the line of maximum intensity the value of T was found.
2. Temperatures of the same shots were calculated also from the slope of the graph of
log, {I/(2J + 1)] vs the rotation energy E, where I is the intensity of the line, (25 + 1) is the
degeneracy factor, and E is the rotational energy appropriate to the vaiue of J of the initial or
lower level in absorption. The slope of this graph is 1/KT, where K is the Boltzmann factor
and T is the temperature.
Spectra at high dispersion are not well suited for measurements of the frequency distribution of a continuous spectrum; hence such distributions are outside the scope of this report.
The transmission of the atmosphere is not considered in this report since it does not affect
the relative strength of absorption lines or bands, nor does it affect appreciably the relative
strengths of observed emissionlines.
13
73