Effect of polarization on spectroscopic characterization of laser produced aluminium plasma

TL;DR

This study explores how the polarization of emitted light affects the accuracy of plasma parameter measurements in laser-produced aluminium plasma, emphasizing the importance of considering polarization effects for precise spectroscopic analysis.

Contribution

It demonstrates the impact of polarization on plasma temperature estimation and highlights the necessity of assessing polarization before spectroscopic analysis in LIBS.

Findings

Higher DOP correlates with larger errors in temperature estimation.

Electron density estimates remain consistent despite polarization variations.

Deviation from Maxwell-Boltzmann distribution affects temperature measurements.

Abstract

Laser-induced breakdown spectroscopy (LIBS) is a well-established technique widely used in fundamental research and diverse practical fields. Polarization-resolved LIBS, a variant of this technique, aims to improve the sensitivity, which is a critical aspect in numerous scientific domains. In our recent work we demonstrated that the degree of polarization (DOP) in the emission depends on the spatial location and time in a nano second laser generated aluminium plasma1. Present study investigates the effect of polarized emission on the estimation of plasma parameters. The plasma parameters are estimated using the conventional spectroscopic methods such as Boltzmann plot and line intensity ratio for the estimation of electron temperature and Stark broadening for estimating the electron density. The estimated plasma temperature using Boltzmann plot method shows large errors in electron temperature for the locations where DOP is higher. However, the electron density estimated using the Stark width does not show such variation. The observed ambiguity in temperature estimation using the Boltzmann plot method appears to be a consequence of deviation from expected Maxwell Boltzmann distribution of population of the involved energy levels. These findings highlight the need of assessing the DOP of the plasma before selecting the polarization for PRLIBS or temperature estimation using Boltzmann plots in elemental analysis.