*Send correspondence to hamiche@ca.sandia.gov A scanning mobility particle sizer was used to measure changes in size distributions of soot particles when exposed to laser radiation at 532 or 1064 nm with fluences up to 0.8 J/cm 2 . Laser-induced production of carbon nanoparticles was observed at fluences above 0.12 J/cm 2 at 532 nm and 0.22 J/cm 2 at 1064 nm. Near-edge x-ray absorption fine structure spectra showed predominantly graphitic (sp 2 -hybridized) carbon in the non-irradiated particles and significantly different features in the irradiated particles. These results are consistent with differences in the fine structure between irradiated and non-irradiated samples observed by transmission electron microscopy.Copyright 2

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We have measured time-resolved laser-induced incandescence (LII) from combustion-generated mature soot extracted from a burner and (1) coated with oleic acid or (2) coated with oleic acid and then thermally denuded using a thermodenuder. The soot samples were size selected using a differential mobility analyzer and characterized with a scanning mobility particle sizer, centrifugal particle mass analyzer, and transmission electron microscope. The results demonstrate a strong influence of coatings on the magnitude and temporal evolution of the LII signal. For coated particles, higher laser fluences are required to reach signal levels comparable to those of uncoated particles. The peak LII curve is shifted to increasingly higher fluences with increasing coating thickness until this effect saturates at a coating thickness of *75 % by mass. These effects are predominantly attributable to the additional energy needed to vaporize the coating while heating the particle. LII signals are higher and signal decay rates are significantly slower for thermally denuded particles relative to coated or uncoated particles, particularly at low and intermediate laser fluences. Our results suggest negligible coating enhancement in absorption cross-section for combustion-generated soot at the laser fluences used. Apparent enhancement in absorption with restructuring may be caused by less conductive cooling.

We have measured time-resolved laser-induced incandescence (LII) from combustion-generated mature soot extracted from a burner and (1) coated with oleic acid or (2) coated with oleic acid and then thermally denuded using a thermodenuder. The soot samples were size selected using a differential mobility analyser and characterized with a scanning mobility particle sizer, centrifugal particle mass analyser, and transmission electron microscope. The results demonstrate a strong influence of coatings particle morphology and on the magnitude and temporal evolution of the LII signal. For coated particles higher laser fluences are required to reach LII signal levels comparable to those of uncoated particles. This effect is predominantly attributable to the additional energy needed to vaporize the coating while heating the particle. LII signals are higher and signal decay rates are significantly slower for thermally denuded particles relative to coated or uncoated particles, particularly at low and intermediate laser fluences. 4 ACKNOWLEDGMENTSWe thank Daniel Strong for the rendition of the experimental setup shown in Fig. 1. We are very grateful to Chris Sorensen for his sage advice on fractal analysis. We also appreciate Alexei Khalizov's insightful comments about soot restructuring and Jeff Headrick's assistance with the TEM image analysis.

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