The radical anion [(CCCCC)-C-13](-.), with known bond connectivity, has been synthesized in the ion source of a VG ZAB 2HF mass spectrometer by the reaction of (CH3)(3)Si-Cequivalent toC(13)C (=NNH-tosyl)-Cequivalent toC-Si(CH3)(3) with HO- followed by F- (from SF6). The collision-induced mass spectrum of [CC13CCC]- shows only one fragmentation: exclusive loss of C-12. Computational studies at the CCSD(T)/aug-cc-pVDZ//B3LYP/6-31G(d) level of theory indicate that this experimental observation means that [(CCCCC)-C-13](-.) does not rearrange under the conditions of collisional activation. The charge reversal [-CR+, synchronous charge stripping of the radical anion (by a vertical Franck-Condon process) to the radical cation], and the neutralization/reionization [-NR+, stepwise vertical oxidation of the radical anion to the neutral, then of the neutral to the radical cation] spectra of [(CCCCC)-C-13](-.) show partial and complete atom scrambling, respectively. Under the experimental conditions used, the neutral has a lifetime of 10(-6) s before being converted to tile corresponding radical cation. Computational studies at the CCSD(T)/aug-cc-pVDZ//B3LYP/6-31G(d) level of theory suggest that the major atom-scrambling pathway of the neutral involves cyclization of singlet (CCCCC)-C-13 to equilibrating and degenerate carbon-substituted rhombic structures that fragment to yield linear singlet (CC4)-C-13-C-12 Structures. Overall, the label is randomized. A similar mechanism is proposed to account for the partial atom scrambling of the radical cations formed in the -CR+ experiment from [(CCCCC)-C-13](-.).