Effects of laser pulse sequence on laser-induced soil plasma emission.
In this study, we investigated the effects of a sequence of laser pulses on the plasma emission intensity, plasma temperature, and electron density of laser-induced soil plasma. The experimental results indicate that the plasma radiation was gradually strengthened as the laser-pulse sequence progressed. The theoretical results show that the spectral line intensity and spectral signal-to-background ratio of the elements Fe, Mn, K, and Ti were strongest for plasma from the sixth laser pulse. These data suggest that repeatedly ablating the same surface position of a soil sample with a sequence of laser pulses can enhance the laser-induced breakdown spectroscopy signal.