Differential Raman backscattering cross sections of black carbon nanoparticles.

We report the measurements of the differential Raman backscattering cross sections for several carbonaceous ultrafine particles of environmental relevances. These were obtained by dispersing the target particles in liquid water which was used as the internal standard reference. The optical collection was performed in a configuration to ensure a detection as close as possible to the backward direction. These are the first cross sections on black carbon-type particles although Raman spectroscopy is widely used in Carbon science. The high values of the cross sections, few 10-28 cm2.sr-1.atom-1, reflect resonance effects that take advantages of the disordered polyaromatic structures. Because they were measured in conditions intended to mimic the aerosol phase, these measurements provide a crucial step to move toward quantitative Raman spectroscopy and enable development of dedicated teledetection of black carbon in the atmosphere and in combustion chambers.