Do the interstellar molecules CCCO and CCCS rearrange when energised?

Neutrals CCCO, (CCCO)-C-13, CCCS and (CCCS)-C-13 have been prepared by one-electron vertical (Franck - Condon) oxidation of the precursor anion radicals (CCCO)(-.), ((CCCO)-C-13)(-.), (CCCS)(-.) and ((CCCS)-C-13)(-.) respectively in collision cells of a reverse sector mass spectrometer. Ionisation of the neutrals to decomposing cations shows the neutrals to be stable for the microsecond duration of the neutralisation - ionisation (-NR+) experiment. No rearrangement of the label in energised CC13CO or CC13CS occurs during these experiments. In contrast, minor rearrangement of ((CCCO)-C-13)(+.) is observed [((CCCO)-C-13)(+.)--> ((OCCC)-C-13)(+.)], while significant rearrangement occurs for ((CCCS)-C-13)(+.) [((CCCS)-C-13)(+.) --> ((SCCC)-C-13)(+.)]. Theoretical calculations at the CCSD(T)/ aug-cc-pVDZ//B3LYP/6-31G(d) level of theory show that the cationic rearrangements occur by stepwise processes via key rhombic structures. Overall, the degenerate processes result in O and S migration from C-3 to C-1. The cations (CCCO)(+.) and (CCCS)(+.) require excess energies of greater than or equal to 516 and greater than or equal to 226 kJ mol(-1) respectively to effect rearrangement.