High spectral resolution of diode laser absorption spectroscopy for isotope analysis using a supersonic plasma jet

Abstract

Although high-temperature plasma sources have been used for direct isotope analysis of solid samples, the spectral resolution of diode laser absorption spectroscopy in high-temperature plasma is limited by the Doppler broadening of atomic absorption lines. Thus, a decrease in translational temperature is necessary to enhance the spectral resolution and distinguish isotope shifts due to the mass number. In this study, a supersonic plasma wind tunnel, also called an arc-jet plasma wind tunnel, was used to enhance the spectral resolution drastically, and a demonstration was carried out using natural stable xenon isotopes. As a result, the temperature was found to be about 180 K, and the spectral resolution was about one order of magnitude higher than that of the conventional high-temperature source. Additionally, the method proposed herein was verified by using two xenon isotopes.