Effect of ambient conditions on ultraviolet femtosecond pulse laser induced breakdown spectra

In this work, the results of a study on the influence of buffer gas and pressure on the LIBS spectrum characteristics are reported. Ultraviolet femtosecond pulses were employed in the analysis of several solid samples including brass, copper, aluminum and silicon under different buffer gasses: air, argon and helium. Given a buffer gas, ambient pressure was varied and its effect on the intensity and broadening of the spectral emission lines and on the background of the spectra was evaluated. A maximum emission intensity of the lines was observed at 500 hPa in helium or argon and at 30 hPa in air. Line broadening, attributed to the Stark effect, was found to be negligible in spectra acquired with helium as a buffer gas compared to spectra recorded under air or argon atmosphere, which showed noticeable line broadening particularly at high ambient pressure.