Hannover 2010 – scientific programme
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P: Fachverband Plasmaphysik
P 8: Poster: Low Temperature Plasmas I
P 8.4: Poster
Tuesday, March 9, 2010, 16:00–18:00, Lichthof
Laser induced fluorescence spectroscopy of N2(A3Σu+,ν=0) and absolute density calibration by Rayleigh scattering — •Sebastian Nemschokmichal, Frank Bernhardt, Bert Krames, and Jürgen Meichsner — University of Greifswald, Institute of Physics, Greifswald, Germany
Laser induced fluorescence spectroscopy (LIF) is applied to a 13.56 MHz rf discharge (CCP) in nitrogen from 40 to 1000 Pa to measure absolute densities of the first metastable N2(A3Σu+,ν=0) state. The dye laser excites at 687.44 nm to the N2(B3Πg,ν=3) state which afterwards fluorescences to the N2(A3Σu+,ν=1) state at 762 nm. The fluorescence light is separated via a monochromator and detected by a photomultiplier tube.
Besides axial profiles of relative densities the temporal evolution of the LIF signal is investigated to distinguish the effective lifetime of the excited state depending on pressure. These lifetimes differ partly significantly from the lifetimes calculated by means of the radiative lifetime and the quenching rates from literature.
Absolute density calibration is done by a comparison of the LIF with Rayleigh scattering in nitrogen at 687 nm to be independent from the geometry of the absorption volume and the detection cone. Furthermore, the influence of small admixtures of oxygen (0.5 to 2%) was investigated.