Optical properties of magnetized transient low-pressure plasma

A transient optically thick plasma under the influence of a constant external magnetic field was investigated taking self-absorption into account. Self-absorption which defines the excited state-densities is an important mechanism and can be used with other methods to describe the state densities for an optically thick plasma. This method is an established tool to retrieve state-density and plasma parameters. To measure each magnetic sub-level density of argon 1s₄ and 1s₅ (in Paschen's notation) a tunable diode laser absorption spectroscopy was used. Based on reconstructed excited state densities, the self-absorption coefficient was calculated for individual magnetic sub-levels. A decrease in self-absorption with an external magnetic field was noticed indicating a higher transparency of the plasma. Furthermore a polarization dependent self-absorption was found. The presented results can help to model optical properties and interpret the absorption of a low-pressure optically thick magnetized plasma. (paper)