Hydroxyl Rotational Temperatures in the Airglow

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Date
1971-02Author
Nicholls, David Conway
Type
ThesisDegree Level
MastersMetadata
Show full item recordAbstract
Nightglow spectra of the OH Meinel bands have been
analysed to determine the rotationa1 temperature. It has
been found that the rotational temperatures determined from
different rotational lines in a single band are not constant
but increase with increasing rotational quantum number. A
deviation from isothermal rotational temperatures for excited
molecules in rotational equilibrium is caused by the variation
of kinetic temperature in the OH emission region, but is much
less than that observed. It has been concluded that nonequilibrium
processes are important. A rotational relaxation
model has been proposed to describe the spectrum emitted by
molecules that are not in rotational equilibrium. The model
was used to calculate the OH nightglow spectrum for bands originating
from the eighth and ninth vibrational levels. The
calculated rotational temperatures are in good agreement with
those derived from observed spectra.
The effects of vibrational relaxation in the excited
OH molecules have been considered qualitatively and are in
agreement with the observed behaviour of the measured intensities
and rotational temperatures.
It is suggested that the application of the relaxation
model to other airglow emissions may give new information on
atmospheric processes.