Speaker
Prof.
Timo Gans
(University of York)
Description
Atmospheric pressure plasmas are versatile and efficient sources for reactive species production at ambient room temperature. The non-equilibrium chemical kinetics is initiated and determined by the electron dynamics. Due to the strongly collisional environment and associated short electron energy relaxation times the electron dynamics can be tailored using multi-frequency power coupling techniques, enabling separate control of key parameters like electron density and electron mean energy. Reactive atomic species play key roles in the chemical kinetics and details strongly depend on the feed-gas composition. Measurements and predictive simulations of key reactive species are equally challenging due to the strongly collisional environment and their multi-scale nature in space and time. The most promising approach is the exploitation of complementary advantages in direct measurements combined with specifically designed numerical simulations. Picosecond two-photon absorption laser induced fluorescence (TALIF) spectroscopy allows us to measure absolute densities of atomic oxygen (O), nitrogen (N) and hydrogen (H), even in chemical environments with complex reaction kinetics and associated collisional quenching processes, through directly resolving the effective lifetime with sub-nanosecond resolution. This is particularly important in realistic situations for technological applications with plasma operation and species penetration into ambient air. The picosecond TALIF measurements are compared with direct VUV synchrotron absorption spectroscopy under well-defined gas compositions showing very good agreement. Further insight into the chemical kinetics is obtained through additional UV & IR absorption spectroscopy (OH, O$_3$, CO$_2$, CO) measurements and synergistic combination with multi-scale numerical simulations of the chemical kinetics. The presentation will focus on examples of He-O$_2$-N$_2$-H$_2$0 mixtures for bio-medical applications and He/Ar-CO$_2$ mixtures for CO$_2$ conversion into value-added chemicals.
Primary author
Prof.
Timo Gans
(University of York)
