ABSTRAKT

Plasma diagnostics of arc light sources is of immediate interest in developing a better understanding of the atomic processes that govern their operation. Due to new application ranges, e.g., interior lighting and automobile headlights, these devices, especially the metal-halide lamps, are of increasing practical importance. Mass movement and energy transfer within the arc volume are factors causing deviation of the plasma state from thermodynamic equilibrium. Diagnostics methods that are free from equilibrium assumptions are, therefore, of primary importance. An emission spectroscopy diagnostic method using self-reversed lines was developed. This method is relatively easy to apply, does not require complex technology, and it is free from equilibrium assumptions. Application examples in mercury and mercury-metal halide arc lamps are given and discussed. The obtained results show substantial differences between excitation, electron and LTE temperatures indicating severe departures from excitation equilibrium. These departures depend on the presence of the easily ionizable metal of the metal halide. Indications of strong overpopulation of the resonance and metastable thallium states with respect to the ground state are obtained in an arc lamp containing mercury and thallium iodide.