Time-resolved metastable fractions (MFs) for C + n (n = 48-62) were measured on an ion trap/reflectron mass spectrometer for trapping times up to 100 μs. The plot of the MFs versus ln(t 2 /t 1 ) (where t 1 and t 2 are the times corresponding to the beginning and end of a metastable time window, respectively) is non-linear and approaches MF = 0 asymptotically as ln(t 2 /t 1 ) approaches zero. We demonstrate that this experimental result can be modeled only by taking radiative decay, in addition to dissociative C 2 -evaporative decay, into account.