TEA CO<inf>2</inf> Laser – Polymethyl Methacrylate Interaction: LIBS Hydrogen Analysis

Abstract

The interaction of a Transversely Excited Atmospheric (TEA) CO2 laser with a polymer polymethyl methacrylate (PMMA) sample in a vacuum ambiance was studied. The main goal was to demonstrate the feasibility of laser-induced breakdown spectroscopy (LIBS) to detect hydrogen. The generation of plasma over the PMMA surface, using a low laser intensity of ∼ 48 MW/cm2 and fluence of ∼ 16.5 J/cm2, required the application of a metal sub-target. Besides hydrogen, the recorded spectra were dominated by atomic lines of carbon and oxygen and band emission of the C2 and CN molecules. The electron number density and temperature (ionic, vibrational, and rotational) were evaluated to characterize the laser-induced plasma. In addition, PMMA micro-damages (diameter ∼ 45 µm) created by a multipulse laser ablation could find potential applications in sensor technologies.