Searching for complex fullerene-based molecules in the prototype fullerene Planetary Nebula IC 418

The recent and unexpected detection of the most commonfullerenes (C60 and C70) and protographene in some Planetary Nebulae (PNe) raises the exciting possibility that other more complex fullerenebased molecules (e.g., carbon onions or multishell fullerenes, fullereneadducts) might be ubiquitous inthe Universe and continue to be serious candidates toexplain many astrophysical phenomena. The presence ofcomplex fullerenebased molecules such as carbon onions in the circumstellar shells of fullerenecontaining PNe is strongly suggested by ourrecent analysis of the unusual diffuse interstellar bands detected towards two PNe where C60 had already been found. If complex fullerenebased molecules suchas carbon onions are present in this peculiarclass of stars, they could easily be detected in the farIR range. Fullerenecontaining PNe are usually very faint in the farIR but our very recent detectionof C60 fullerenes in PN IC 418 can now mitigate this unfortunate situation. Surprisingly, Herschel has not observed this very bright source now considered the prototype fullerenecontaining PN as part of any approved program in previous cycles. Thus, a comprehensive farIR study of the complex circumstellar environmentwhere fullerenes and fullerenebased molecules may form is at present lacking. With this DDT proposal we aim at obtaining full range, high S/N, Herschel/PACS farIR spectra of PN IC 418 to search for the spectral signatures of complex fullerenebasedmolecules such as multishell fullerenes (e.g., C60@C240, C240@C960), which are predicted to be detectable as relatively strong broad features in thefarIR range. If successful, these observations will constitute the first firm detection of the most complex molecules ever detected in space. In addition,we will search for the predicted hydrogenated amorphous carbon (HAC) associated feature at virgul60 um toconfirm/refute the HAC.s processing/decomposition scenario as truncated!, Plea [truncated!, Please see actual data for full text]