The oxidized soot surface: theoretical study of desorption mechanisms involving oxygenated functionalities and comparison with temperature programed desorption experiments.

The desorption mechanism for oxygenated functionalities on soot is investigated by quantum mechanical calculations on functionalized polycyclic aromatic hydrocarbon (PAH) models and compared with recently published temperature programed desorption-mass spectrometry results. Substituents on PAHs of increasing size (up to 46 carbon atoms in the parent PAH) are chosen to reproduce the local features of an oxidized graphenic soot platelet. Initially, the study is carried out on unimolecular fragmentation (extrusion, in some cases) processes producing HO, CO, or CO2, in model ketones, carboxylic acids, lactones, anhydrides, in one aldehyde, one peroxyacid, one hydroperoxide, one secondary alcohol, and one phenol.

Ozone interaction with polycyclic aromatic hydrocarbons and soot in atmospheric processes: theoretical density functional study by molecular and periodic methodologies.

The ozonization mechanism for polycyclic aromatic hydrocarbons (PAHs) and soot is investigated by quantum mechanical calculations carried out on molecular and periodic systems. PAHs, interesting per se, serve also to model the local features of the graphenic soot platelets, for which another model is provided by a periodic representation of one graphenic layer. A concerted addition leads to a primary ozonide, while a nonconcerted attack produces a trioxyl diradical (in which one of the two unpaired electrons is pi-delocalized).