Formation and emission spectroscopy of laser generated nanoparticles

Iron nanoparticles, with both fee and bee structure and with a protective carbon shell against oxidation, were generated by laser-assisted photolytic chemical vapor decomposition of ferrocene (FeCp2). Amorphous W and V;NO,3 nanoparticles were formed by laser ablation of solid W in Ar and in N-2 ambient, respectively. Laser-assisted chemical vapor deposition of W yielded crystalline tungsten nanoparticles (beta phase) from WF6/H-2/Ar gas mixture. ArF excimer laser was used as radiation source for all the experiments. Measurements and analysis of the emitted blackbody-like radiation from the laser heated particles were performed, dominant cooling processes as evaporation and heat transfer by the ambient gases were identified. The particles could be heated up to the boiling and melting point of iron and tungsten, respectively. Lognormal particle size-distributions were found for Fe/C and W nanoparticles generated by vapor decomposition or deposition processes respectively, furthermore modeled at low particle concentration (with no coagulation) limit. The thickness of the carbon shell was practically independent on the laser fluence, while the size of the iron core could be varied with it for the Fe/C particles. The laser ablation yielded no lognormal type of distribution for the amorphous WN0,3 particles.