Enhancement of optical emission from laser-induced breakdown spectroscopy by plasmas generated in flame

Enhancement of optical emission was observed by laser-induced plasmas generated in the blue outer envelope of a n eutral oxy-acetylene flame. A KrF Excimer laser with a wavelength of 248 nm and a pulse duration of 23 ns was used to induce the plasmas. Fast imaging and spectra analyses were carried out to investigate plasma evolution and optical emission. The images of plasma evolution show that plasmas in flame have larger size and stronger emission intensity in the initial plasma lifetime. However, the plasma emission intensity also decays faster in flame. Spectra analyses show enhanced optical emission and narrowed line broadening from plasmas in flame. Up to 4 times of optical emission enhancement of the Al I 394.4 nm and down to 60% of its full width at half maximum (FWHM) were achieved. Moreover, the calculated electron temperature and density indicate that higher temperature and lower density plasmas were produced in the flame environment in the early plasma lifetime.