Developing the model of laser ablation by considering the interplay between emission and expansion of aluminum plasma

In the present study, the ablation behavior of aluminum target and its plasma radiation in noble ambient gases by a laser pulse with wavelength of 266 nm and pulse duration of 10 ns are numerically studied. A thermal model of laser ablation considering heat conduction, Euler equations, Saha-Eggert equations, Knudsen layer, mass and energy balance relations and optical shielding effects are used for calculation of plasma parameters. Effects of excitation energy on plasma expansion and its emissivity are investigated. Time and spatial-resolved plasma emission including bremsstrahlung, recombination and spectral emission at early delay times after laser irradiation is obtained. Effects of two ambient gases (He and Ar) as well as different gas pressures of 100, 300, 500, and 760 Torr on plasma expansion and its spectrum are studied. Results illustrate that at initial delay times, especially at high noble gas pressures, ionic lines have the maximum intensities, while at later times neutral lines dominate. When the pressure of ambient gas increases, a confinement of the plasma plume is predicted and the intensity of neutral lines decreases. Continuous emission increases with wavelength in both ambient gases. Spatially resolved analysis shows that an intense continuous emission is predicted next to the sample surface decreasing with distance from the latter. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4773036]