Nanosecond femtosecond fs and fs filamentation LIBS studies combined with machine learning for the identification of plastic waste and standoff detection of HEMs

Abstract

Spectroscopy is a branch of physics that deals with the interaction of electromagnetic newlineradiation (EM) with matter[1]. Spectroscopic studies provide deep insights into the newlineproperties of the analyte (samples/materials) considered for the investigation. It finds newlineapplication in a wide range of interests such as medicine, chemistry, biology, newlinenanotechnology, materials science, environmental studies, and physics. The invention of newlinethe laser in the early 1960s has opened up new avenues in the field of spectroscopy[2]. newlineLaser-matter interaction has become exciting research filed which has revolutionized the newlinedifferent research areas like photonics, nanoengineering, semiconductor physics, plasma newlinedynamics, chemistry, and optical physics, etc. The interaction of high-intensity laser pulse newlineon the sample results in the formation of transient, inhomogeneous, hot, and luminous newlineplasma also referred to as laser-induced plasma (LIP)[3]. Instantly after the formation of newlineLIP, it expands into the surrounding medium and cools down with the emission of intense newlineEM radiation (in ~0.5 -1 and#956;s) accompanied by the generation of a shock wave (in ~3-5 and#956;s) newlinewhich immediately decays to acoustic signal (in ~20-40 and#956;s). The characteristic emission newlinefrom the plasma (after ~ 0.5 and#956;s) provides the atomic elemental information of the sample newlineand this analytical spectroscopic technique called as the Laser-induced breakdown newlinespectroscopy (LIBS)[4, 5]. newline