Particle formation from pulsed laser irradiation of soot aggregates studied with a scanning mobility particle sizer, a transmission electron microscope, and a scanning transmission x-ray microscope

<p>&nbsp;</p><!--StartFragment--><p><span style="font-size:12.0pt;font-family:&quot;Times New Roman&quot;;
mso-ansi-language:EN-US;mso-fareast-language:EN-US">We investigated the physical and chemical changes induced in soot aggregates exposed to laser radiation using a scanning mobility particle sizer, a transmission electron microscope, and a scanning transmission x-ray microscope to perform near edge x-ray absorption fine structure spectroscopy. <span style="mso-spacerun:
yes">&nbsp;</span>Laser-induced nanoparticle production was observed at fluences above 0.12 J/cm² at 532 nm and 0.22 J/cm² at 1064 nm.<span style="mso-spacerun: yes">&nbsp; </span>Our results indicate that new particle formation proceeds via (1) vaporization of small carbon clusters by thermal or photolytic mechanisms, followed by homogeneous nucleation, (2) heterogeneous nucleation of vaporized carbon clusters onto material ablated from primary particles, or (3) both processes.&nbsp;</span></p><!--EndFragment-->