Influence of the Distance between Focusing Lens and Target Surface on the Characteristics of Laser-excited Lead Plasma

Qusay Adnan Abbas

doi:10.24996/ijs.2021.62.12.10

Abstract

The present work investigated the effect of distance from target surface on the parameters of lead plasma excited by 1064nm Q-switched Nd:YAG laser. The excitation was conducted in air, at atmospheric pressure, with pulse length of 5 ns, and at different pulse laser energies. Electron temperature was calculated by Boltzmann plot method based on the PbI emission spectral lines (369.03 nm, 416.98 nm, 523.48, and 561.94 nm). The PbI lines were recorded at different distances from the target surface at laser pulse energies of 260 and 280 mJ. The emission intensity of plasma increased with increasing the lens-to-target distance. The results also detected an increase in electron temperature with increasing the distance between the focal lens and the surface of the target in all laser energies under study. In addition, the electron number density was determined by using the Stark broadening method. The data illustrated that the electron number density was increased with increasing the distance from target surface, reaching the maximum at a distance of 11 cm for all pulse laser energy levels under study.

Highlights

In recent years, laser induced plasma spectroscopy (LIPS), or laser induced breakdown spectroscopy (LIBS), has been widely studied, as shown by many experimental and theoretical researches published on the topic [1,2,3]
As a Q-switched Nd:YAG laser focuses at atmospheric pressure on a Pd target surface, emission intensity in the focal spot induces rapid local heating on the target surface of the Pb and creates a plasma that contains electrons, ions, atoms and molecules
Valuable references for improving the analysis techniques in the field of LIBS can be given by adjusting the distance between the focusing laser lens and the target surface

Summary

Introduction

Laser induced plasma spectroscopy (LIPS), or laser induced breakdown spectroscopy (LIBS), has been widely studied, as shown by many experimental and theoretical researches published on the topic [1,2,3]. The guided laser beam results in the evaporation, atomization, and ionization of the target's surface content, where the emitted radiation is used to detect the elemental composition of the samples [2,6]. This technique has several advantages over other traditional techniques of atomic emission spectroscopy; it is applicable to the study of conducting and non-conducting target samples and does not require sample preparation [4]

Methods

Results

Conclusion