A powerful laser beam, most often from a pulsed Nd:YAG laser—with an emission wavelength of 1064 or 532 nm, a single - pulse energy of 50 to 100 millijoules, and a pulse duration less than 10 nanoseconds—is focused onto the sample material, generating a plasma spark at the surface. Because the temperature in the plasma is typically around 10,000 K, the species present are turned into electronically excited atoms and ions.  

As the excited species decay, they emit radiation at wavelengths that are distinct to each chemical element, typically in the ultraviolet to near-infrared range. Light from the spark is gathered by a spectrometer and analyzed by a computer.