# Optical properties of magnetized transient low-pressure plasma

## TL;DR

This study investigates how an external magnetic field alters the optical properties of low-pressure plasma by causing Zeeman splitting, affecting spectral lines, self-absorption, and transparency, with measurements using laser absorption spectroscopy.

## Contribution

It provides new insights into the magnetic field's effect on spectral line profiles and self-absorption in magnetized plasma, enhancing modeling and interpretation of optical properties.

## Key findings

- Magnetic field decreases self-absorption, increasing plasma transparency.
- Polarization affects self-absorption dependent on magnetic sub-levels.
- Reconstructed excited state densities aid in plasma modeling.

## Abstract

A plasma under the influence of an external magnetic field changes the optical properties due to the Zeeman splitting of the energy levels. This splitting degenerates an initial single spectral line into a system of spectral lines with different transition frequencies defined by the electronic structure of the energy levels. Newly created magnetic sub-levels redefine the spectral profile of the line emission and therefore radiation transport mechanism in optically thick plasma. 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 (TDLAS) 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.