Laser Wavelength and Argon Ambient Gas Pressure Effects on Metallic Plasma Emission

Abstract

The effects of laser wavelength and argon ambient gas pressure on ionic and atomic emission from aluminum and copper metal plasmas has been studied. The plasmas were generated using metal targets excited with a Q-switched Nd:YAG laser operating at the first fundamental (1064 nm), second (532 nm), third (355 nm), and fourth harmonics (266 nm) with repetition rate up to 10 Hz. The spectroscopic analysis of the plasma plume emission revealed that the intensities and signal-to-noise (S/N) ratio of various neutral and ion spectral lines, small components, and trace impurities increase sharply when the fourth laser harmonic is used at a wavelength of 266 nm. Based on LTE assumption, the electron excitation temperature (Te) and electron number density (Ne) of the produced plasma have been estimated from the Boltzmann plot using neutral spectral lines of Al I at 256.8, 257.5, 309.3, and 396.15 nm and Cu I at 427.58, 510.59, 570.07, and 578.58 nm and from Stark broadening width profile of Al II at 281.6 nm and Cu I at 324.75 nm, respectively. The variations of Te, Ne, and emission intensities of metals as a function of laser irradiance of different laser wavelengths at 1064, 532, 355, and 266 nm were studied. The effect of the argon ambient gas pressure on the plasma parameters was also studied. The diagnostics of the produced metal plasma was undertaken using laser induced breakdown spectroscopy (LIBS).