NIR FT Raman spectroscopic study of flame soot

During combustion soot goes through different molecular structures. The Ram an spectra of flame soot, collected in premixed flames at different flame h eights and flame temperatures, were analysed in regard to their structural properties and in comparison with those of disordered graphite. Besides the G- and D-band of disordered graphite, a third Raman band at approximately 1188 cm(-1) was observed which was tentatively assigned to mixed sp(2)-sp(3 ) bondings or to the C-C and C=C stretching vibration modes of polyene-like structures. The G-band position, the D-band width, and I-D/I-G intensity r atio describe the graphitic order in the particles. According to this resul t the graphitic order of the untreated soot particles decreases with decrea sing flame temperature and flame height, whereas the size L-a of the graphi tic sheets is nearly constant.