Absorption spectra

Spectroscopic observations were made of the resonance absorption of
sunlight by the atmospheric hydroxyl radical (OH). The abundance of
0 terrestrial OH was measured from the Fritz Peak Observatory (39.92 N,
105.50°W) in Colorado during September of 1978. These measurements
were made on the absorption of the P1 (1) line of the A^2sigma^+ - x^2pi(O , O)
rotational band of OH at 3081.7 A. The instrument used was the
PEPSIOS (Poly Etalon Pressure Scanned Interferometric Optical Spectrometer)
because of its high luminosity - resolution product . The
computer methods ·~sed in the analysis procedure are described . These
measurements indicated an average daytime vertical column abundance
of (5.40 ± 0.67) x 10^13 OH molecules/cm^2.

A method is presented, in which the Pepsios is used to measure
abundances of atomic sodium present in the upper atmosphere
as calculated from the twilight glow. These abundances are
compared with daylight absorption abundances, also measured
using the Pepsios. Ten measurements taken during March,
1971 show an average twilight abundance of (6.1 +- 1.8) x 10^9
atoms/cm^2. This compares with an average absorption
abundance of (3.3 +- 1.1) x 10^9 atoms/cm^2. These limited
data and their attendant uncertainties reveal no significant
discrepancy between twilight and daytime sodium abundances.

A high resolution study of nighttime and daytime absorption of the sodium n2
line was made at Florida Atlantic University, Boca Raton, Florida (26°22'N
latitude, 80°6 1W longitude) from October 1970 to April 1971 using a Pepsios
(polyetalon pressure scanning interferometric optical spectrometer). Line
scans were taken with photoelectric detection of the sodium D^2 line using
sunlight in the daytime and moonlight in the nighttime. A computer analysis
of the line scans determined the terrestrial free sodium abundance and the
related uncertainty. The average monthly daytime sodium abundance for the
winter was 5.32 ± 1.0 x 10^9 atoms/cm^2. Nighttime averages made by several
procedures yielded sodium abundances for the winter months in the range
5.2 - 6.2 ± 4.0 x 10^9 atoms/cm^2. Separate averages made of the evening and
morning moonlight traces were apparently affected in different ways by
cumulus clouds or by sodium nightglow. This uncertainty of interpretation
along with the generally poor signal to noise ratio for the moonlight data
suggests that a low degree of confidence be given to the apparent agreement
in average sodium abundances derived from these sunlight and moonlight
measurements.