Population Diagnostics of a Hot NaBr Plasma by Detailed Simulation of Absorption Spectra

The experimental absorption spectra of a hot NaBr plasma are theoretically studied by using a detailed level accounting model. The sodium and bromine absorption spectra have been well reproduced respectively in the approach of local thermodynamic equilibrium, in which the populations between and within ions are obtained by solving the Saha--Boltzmann equation. The temperature of bromine however is found to be much lower than the one of sodium. Such discrepancy indicates that thermodynamic equilibrium is not reached between the sodium and bromine atoms during the measurement.