  The chemical composition of Titan organic haze is poorly known. To address
this issue, laboratory analogs named tholins are synthesized, and analyzed by
methods requiring often an extraction process in a carrier solvent. These
methods exclude the analysis of the insoluble tholins fraction and assume a
hypothetical chemical equivalence between soluble and insoluble fractions. In
this work, we present a powerful complementary analysis method recently
developed on the DESIRS VUV synchrotron beamline at SOLEIL. It involves a soft
pyrolysis of tholins at ~230 deg C and an electron ion coincidence analysis of
the emitted volatiles compounds photoionized by the tunable synchrotron
radiation. By comparison with reference photoelectron spectra (PES), the
spectral information collected on the detected molecules yields their isomeric
structure. The method is more readily applied to light species, while for
heavier ones the number of possibilities and the lack of PES reference spectra
in the literature limit its analysis. A notable pattern in the analyzed tholins
is the presence of species containing adjacent doubly-bonded N atoms, which
might be a signature of heterogeneous incorporation of N2 in tholins.
