Investigation of the signal uncertainty in laser-induced breakdown spectroscopy based on error propagation considering self-absorption

The relatively high signal uncertainty of laser-induced breakdown spectroscopy (LIBS) is a key obstacle to its analytical performance and large-scale application. Despite the extensive research efforts to reduce signal uncertainty, few fundamental studies have been conducted because of the complexity of the microscopic mechanisms involved in plasma evolution. Recently, error propagation analysis has provided an inspiring perspective by linking signal uncertainty with plasma property fluctuations, while further investigation is urgently needed due to the limitations of the employed plasma diagnostic techniques. In this study, a spectrum fitting model was proposed for optically thick and homogeneous plasmas to provide more reliable plasma properties for error propagation analysis for the first time. The model was applied to laser-induced copper plasmas using a laser wavelength of 1064 nm and a pulse duration of 25 ns. The uncertainty of an atomic copper line was analyzed at different delay times. Our findings revealed that the fluctuation of columnar total number density was the most significant factor under the investigated conditions, and that the correlation term of temperature and columnar total number density made a considerable negative contribution. Furthermore, self-absorption suppressed the magnitudes of major contribution terms for the signal uncertainty of LIBS.

Automated summary

The high signal uncertainty of laser-induced breakdown spectroscopy (LIBS) hinders its analytical performance and large-scale application. The complexity of plasma evolution hampers fundamental research to reduce signal uncertainty. Error propagation analysis offers a new perspective by linking signal uncertainty with plasma property fluctuations, but further investigation is urgently needed due to limitations of plasma diagnostic techniques. A spectrum fitting model for optically thick and homogeneous plasmas was proposed in this study, providing more reliable plasma properties for error propagation analysis. The model was applied to laser-induced copper plasmas and revealed the significant influence of columnar total number density fluctuation and correlation term of temperature and columnar total number density on signal uncertainty, as well as the suppression effect of self-absorption.