Comparison of Libs and Polarization Resolved Libs Emission Spectra for Aluminium Alloy

Time and polarization resolved optical emission spectroscopy of laser-produced plasmas formed on Al alloys has been studied in the visible spectral range at a background air pressure of 10^-4 mbar. A comparative experimental investigation has been made between the results obtained from the polarization-resolved laser-induced breakdown spectroscopy (PRLIBS) and those obtained for the unresolved case (denoted simply as LIBS here). The spectral signal-to-background ratio (SBR) is increased significantly for PRLIBS compared with LIBS for the Mn emission line at a wavelength of 415 nm, which had trace concentrations in the sample. The results have been interpreted within the framework of radiatively recombining plasma where free electrons are captured by ions to emit radiation. In addition, the degree of polarization is quantified for two matrix lines, namely Al⁰ (at 396.15 nm) and Al²⁺ (569.6 nm) by using neighbouring unpolarized emission lines. The plasma parameters are measured and compared with the degree of polarization to determine the dominant mechanism for the polarized emission. Thus, from these results, we feel confident that PRLIBS is a useful and simple addition, capable of improving experimental LIBS performance.