Kinetics and radiactive processes of a XE and I2 inductive RF discharge at low pressure
Barnes, Paul Nathan
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Permalink
https://hdl.handle.net/2142/18838
Description
Title
Kinetics and radiactive processes of a XE and I2 inductive RF discharge at low pressure
Author(s)
Barnes, Paul Nathan
Issue Date
1996-05
Doctoral Committee Chair(s)
Kushner, P.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
kinetics
radioactive processes
Xe
I2
ionic recombination
Language
en
Abstract
An investigation is conducted to determine the kinetics and radiative processes involved in a low pressure, 0.5 - 5 torr, discharge sustained in Xe and I 2 • The discharge is excited with an RF inductive power source. The diagnostics applied in this study include laser-induced fluorescence (LIF) I absorption spectroscopy, emission spectroscopy, microwave interferometry, and microwave absorption. Results from this research indicate that Xe + I 2** ~ Xei* + I is the major precursor reaction leading to Xei* radiation. This conclusion differs from those resulting from research performed at higher pressures. Those studies concluded that the harpoon reaction or ionic recombination is the precursor process. In a time modulated inductively coupled discharge, the emission of I* decays on the order of hundreds of microseconds due to ion-ion neutralization consistent with the Landau-Zener theory of ion-ion neutralization. Decay of the
electron density is also hundreds of microseconds for the same discharge. Electron-ion recombination leading to excited states is not an important source of emission in the discharge
at high or low powers.
The similarity in the observed 512 nm and 804 nm emission indicates that the upper levels of atomic iodine are populated in the same proportions across the radius of the discharge. The difference between the I* emission at 206 nm and I** emission indicates that the upper levels of atomic iodine leading to I** emission are populated in a different proportion than the first excited states of atomic iodine. The emission of the D, E, and F states of I 2 behave similarly, indicating that the relative populations of these upper states are generally maintained across the plasma radius. The Xe**(6p12 ) density results from electron excitation of the Xe* metastable state at higher powers. At lower powers, the population of the Xe** ( 6p12 ) state is largely by direct electron impact with ground state xenon. The emissions from a capacitively coupled discharge at low powers are largely a result of direct electron excitation of species.
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