Laser-induced breakdown spectroscopy for microanalysis using submillijoule UV laser pulses

This paper presents a study of laser-induced breakdown spectroscopy (LIBS) at low energies using KrF laser pulses of only 50-300 muJ. Very small focal spots with diameters of 5 to 20 mum are employed in order to achieve strong plasma emission. The focused intensities were in the range of 1.6 to 150 GW/cm(2). The evolution of the micro-plasma progresses more rapidly in this energy range compared to conventional LIBS using mJ laser pulses. The optimum delay time for the detection of emission from minor constituent elements in aluminum is between 100 and 360 ns after the laser pulse hits the sample. The corresponding limits of detection are in the range of 2 to 450 ppm and are comparable to experiments that have used much higher laser energies. The amount of ablated material is significantly reduced using low laser energies and typical crater diameters are approximately 15-40 mum.