Spectrometric Measurement of Plasma Parameters Utilizing the Target Ambient Gas O I & N I Atomic Lines in LIBS Experiment

Abstract

In this article, we shall report the results of the spectroscopic measurements of the plasma parameters utilizing the spectral lines emitted from the air atoms surrounding plasma (O I line at 777.19 nm and N I at 746.83 nm). The plasma was created via irradiation of plane solid aluminum target in open air by a high peak power Nd: YAG laser pulses at fundamental wavelength of 1064 nm. The emission spectra were recorded using Echelle type spectrograph in conjunction with a time gated ICCD camera at different delay time from 1 to 5 μs and at a fixed gate time of 1 μs. The plasma electron density was measured utilizing the Stark broadening of the N I and O I lines and then compared to the reference density as deduced from the optically thin H α-line at 656.27 nm appeared in the same emission spectra. The results show that under our experimental conditions the air lines are subjected to moderate absorption. The plasma electron temperature was measured utilizing the relative spectral intensity of the air (O I to N I) lines after correcting their spectral radiance against absorption. The standard temperature was measured utilizing the Al II ionic lines. A comparison to the reference temperatures shows a very close agreement after correcting the emission spectral radiance of the air lines against self absorption, which emphasizes the importance of correction process.

Advances in atomic physics

“…This work shows that the Mg I and Mg II lines appeared at the short wave length region of the LIBS spectrum are good candidates for measuring the temperature of the plasma in LIBS experiments, but after correction against self-absorption. The spectrometric measurements of plasma parameters utilizing the target ambient gas O I and N I atomic lines show the reliability in the values of the electron density and the temperature of the plasma generated by the interaction of laser beam with solid targets, El-Sherbini et al [127] .…”