The method involves subjecting the surface of the substance under investigation to a pulses laser beam focussed at the surface. The energy of the laser beam absorbed by the substance stimulates it to emit luminescence and generates a short lived plasma cloud with the materials contained by the substance. The characteristic light emissions in spectral lines or continua are detected by a photodetector system and the quantitative composition determined from the measured radiation intensities. The variation of intensity with time is measured at defined time intervals.
