Investigation of transient phenomena in microplasmas by absorption spectroscopy and by laser-assisted "pump-probe"-experiments

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Metastable Hem and Arm species have turned out to be important for the understanding of energy transport in microplasmas as they constitute an important reservoir of potential energy. They seem to influence strongly the dynamics and the stability of the discharges i.e. they play an important role in transient phenomena. These are in particular the evolution of the discharge in the ignition phase, the -γ-transition and the transition into the arcing mode. Absorption spectroscopy is a powerful tool to gain spatially and time resolved information on metastables and other reactive species. The interaction with short intense laser pulses can trigger ignition and the transition into other transient states of the plasma. Laser assisted \pump-probe" experiments involving simultaneously generated super continuum radiation and/or fast optical emission spectroscopy may yield highly time resolved and spatially well defined information on the transient phenomena. The project part A2 consists of two parts: 1) Absorption spectroscopy at various microplasma configurations used in the Research Unit using tunable diode lasers and broad band absorption spectroscopy, and 2) laser assisted " pump-probe" ignition and plasma-surface interaction studies using the custom designed FemtoProbe system. Both project parts are well defined but very closely interlinked. They both draw on the successful preparatory work in the first funding phase. Both project parts have intimate connection to other project parts of the Research Unit.