LASER INDUCED BREAKDOWN SPECTROSCOPY OF GEOLOGICAL SAMPLES

Abstract

A highly sensitive laser-based spectroscopic technique, the laser induced breakdown spectroscopy (LIBS), for trace element detection has been developed at our laboratory. This method is based on the study of plasma resulting from interaction of intense laser radiation with sample medium. This technique is demonstrated to be able to detect all the significant major and trace elements including Ni, Cu, Mg, Mo, Cr, K, Na, Ca and Fe, present in the rock samples collected from different parts of the Arabian shield. Atomic emission spectra of different trace elements contained in the rock samples have been recorded in the 300 –700 nm region. The 308 nm (XeCl) laser radiation from a Lambda Physik Model EMG 203 excimer laser at an irradiance of 7.6 × 10 10 W. cm –2 has been used. The atomic emission lines were recorded using grating monochromator and detected with photomultiplier. The electrical signal generated by photomultiplier was fed into Box-car averager and processed by signal processor. The observed spectral lines have been assigned to transitions in the neutral charge state of the corresponding atoms of the material under investigation.