  The complex organic chemistry harbored by the atmosphere of Titan has been
investigated in depth by Cassini observations. Among them, a series of solar
occultations performed by the VIMS instrument throughout the 13 years of
Cassini revealed a strong absorption centered at 3.4 $\mu$m. Several molecules
present in Titan's atmosphere create spectral features in that wavelength
region, but their individual contributions are difficult to disentangle. In
this work, we quantify the contribution of the various molecular species to the
3.4 $\mu$m band using a radiative transfer model. Ethane and propane are a
significant component of the band but they are not enough to fit the shape
perfectly, then we need something else. Polycyclic Aromatic Hydrocarbons (PAHs)
and more complex polyaromatic hydrocarbons like Hydrogenated Amorphous Carbons
(HACs) are the most plausible candidates because they are rich in C-H bonds.
PAHs signature have already been detected above ~900 km, and they are
recognized as aerosols particles precursors. High similarities between
individual spectra impede abundances determinations.
