Burnett, Clyde R.

Time-resolved absolute intensity measurements have been made
on the Balmer series lines of a residual hydrogen impurity in a hollowcathode
helium afterglow plasma. From these measurements, the excited
state populations were calculated and revealed the existence of population
inversions in the excited states of hydrogen. In the hydrogen
afterglow the maximum average state population shifted upwards from
n = 3 at the beginning of the afterglow to progressively higher states
until in the late afterglow the maximum population was at n = 6. The
effects of the helium metastables, both atomic and molecular, were
shown to offer no detectable contribution to the observed inversions.
Comparison with a theoretical model for a recombining pulsed hydrogen
plasma for which inversions had been predicted are favorable and
recomb ~nation processes are assumed responsible for the inversions in
the lower discrete levels in the hydrogen impurity.

An experimental investigation of the abundance of upper atmospheric sodium at Boca Raton, Florida, using high resolution absorption spectroscopy, is described. The discussion is based primarily on data taken from January to October, 1968, but W. Lammer's data of September through November, 1967, is used for the seasonal analysis. A description of the data and the method of analysing it are presented, with emphasis on the theory underlying a computer method of analysis.
Measurements indicate a seasonal variation of about a factor of two, with a sharp drop off in late February, 1968. A maximum average monthly abundance of 5.4 ± 2.0 x 10^9 atoms/cm^2 in a vertical column in October, 1967, and a minimum average of 2.6 ± 0.6 x 10 atoms/cm^2 in March, 1968, was measured. The average for the twelve months beginning November, 1967, was 3.6 x 10^9 atoms/cm^2 . In general, uncertainties of the order of 50% are present in the measured abundance determined by a single recorder trace. This value is generally smaller for those traces which are less noisy, and which show a larger amount of terrestrial sodium absorption. No correlation between the abundance and hurricanes has been established. If any correlation exists, it probably is smaller than the uncertainty of our measurements.

An experimental investigation is described in
which a Pepsios high resolution pressure scanning s pectrometer
is used to measure the absorption of light due to
atomic sodium in the upper atmospher e. Design and construction
of the spectrometer will be discussed with attention
given to unique features of the instrument which were
develo ped in this study. An attempt is made to see if any
dependence on the abundance of the sodium can be accounted
for by the proximity to the ocean or by the winds and
extreme turbulence developed by tropical storms and hurricanes.
It is hoped that this data will compliment the
existing data found at other latitudes so that a circulation
dependence may be found.

OH vertical column abundances have been measured since 1977. Based on this long-term data base, the terrestrial OH abundance trends, such as the high-sun (secX = 1) enhancement of the zenith angle dependence, seasonal variations, and diurnal behaviors, have been observed. Current atmospheric models do not predict these features. In this thesis, a one dimensional photochemical model of the mesosphere has been constructed in order to examine the possibility that these observed effects might originate in this region of the atmosphere. Transport effects are not considered. The model result demonstrates that the observed OH behaviors are not caused by known photochemical reactions in the mesosphere.

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 spectroscopic study of a helium-hydrogen afterglow plasma
in a pulsed discharge hollow-cathode has been made to determine
the energy transfer process which results in a population
inversion in atomic hydrogen. Time-resolved emission
measurements were made for the Balmer series in hydrogen
and self-absorption measurements with lambda 3889 A (2s 3S -
3p 3P) and lambda 4650 A (2s 3sigma - 3p 3n) of helium were taken to
monitor the metastable populations. Observations were made
as a function of impurity concentration and as a function of
helium pressure. The energy transfer from the 3S atomic
metastables appears highly probable with only a minor contribution from the 3sigma molecular metastables.

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.

The purpose of this experimental study of the helium afterglow
in a hollow cathode discharge is to identify the mechanisms which
cause an apparent unequal acoustic modulation of the red and violet
wings of observed optical spectrum lines. The unequal red-violet effect is traceable to the fact that curved
spectrum lines are formed at the exit slit of a monochromator which
is equipped with straight entrance and exit slits. Curved spectrum
lines emphasize the red and violet wings differently, depending on
the light contributions from different portions of the entrance slit, so
that spatial variations in the optical image due to acoustic standing
waves show unequal integrated light intensities for the modulation of
each wing. Only the central portion of the radial standing wave in the afterglow
(Bessel function J (kr) distribution) was explored, and the ratio
of the red to violet amplitude calculated as 1 : 1.58 agrees qualitatively
with experimental results.