Kiel 2011 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
P: Fachverband Plasmaphysik
P 9: Poster: Diagnostik technischer Plasmen
P 9.9: Poster
Dienstag, 29. März 2011, 17:00–19:00, Foyer
Negative ion analysis in oxygen cc-rf plasma by laser photodetachment and simultaneous 160 GHz Gaussian beam microwave interferometry — •Christian Küllig, Kristian Dittmann, and Jürgen Meichsner — Ernst-Moritz-Arndt-University of Greifswald, 17489 Greifswald
The laser photodetachment and 160 GHz Gaussian beam microwave interferometry was simultaneously applied to study the negative ion density in low pressure capacitively coupled radio frequency (cc-rf) plasma in oxygen. The line integrated negative atomic oxygen ion density in the overlapping volume of the Gaussian microwave and laser beam ranges between 2×1014 and 1015 m−2. Furthermore, the analysis of characteristic decay time constant of the detachment signals reveals two modes characterized by different electronegativity α=n−/ne. In the case of α>1 the decay time constant amounts to a few µs, only, whereas in oxygen plasmas with low electronegativity, α<1, the relaxation of the electron density needs much longer with typical decay time constants up to about 100 µs. For high electronegativity the electron density relaxation can be described by means of a 0D-attachment-detachment model taking into consideration constant density for positive ions and neutral oxygen species. The dissociative attachment and collisional detachment rates are evaluated by use of the appropriate rate coefficients from literature and the experimental determined effective rate coefficients of the assumed first order kinetics. The metastable O2(a1Δg) plays an important role, for both the formation and loss of negative atomic oxygen ions.