Influence of ambient conditions on the laser air spark

To understand the capability of laser spark spectroscopy or laser-induced b reakdown spectroscopy (LIBS) for quantitative, in situ metals measurements in air, we examined the effects of ambient conditions on the laser air spar k. We used measurements of light emission to determine temporally- and spat ially-resolved values of the plasma temperature and electron density at atm ospheric pressure. Many of these measurements were Abel-inverted to determi ne non-path-integrated values. Electron densities were obtained from Stark- broadened lineshapes. Temperatures were determined using a multi-line graph ical Saha-Boltzmann approach. Good agreement was found between electron den sities measured using different atoms and emitted lines, between temperatur es measured using different elements, and between ionization and excitation temperatures for those elements. Changing the ambient gas, the laser energ y, particulate levels, and humidity levels produces little variation in the temperature and electron density in the laser spark. These results are con firmed by the laser-supported radiation wave model for the radiative expans ion of the laser spark. This lack of sensitivity of the laser spark charact eristics on ambient conditions or laser energy is encouraging for the quant itative use of LIBS.