Model
Digital Document
Publisher
Florida Atlantic University
Description
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.
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.
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