A radical cation with an intramolecular sulfur-nitrogen bond was formed in the photoinitiated transfer of an electron from the sulfur atom of the dipeptide Met-Gly to 4-carboxybenzophenone in its triplet state. The sulfur-nitrogen coupling involved two-center, three-electron bonds. The kinetics of the reactions of these radical cations, which were initiated by a laser flash, were followed over time. The spectrum of the radical cation had to be extracted from the interference of other absorbing transients. The principal method of implementing the spectral resolutions was accomplished through a multiple linear regression technique. This spectral analysis was repeated for numerous time windows during the lifetime of the transients’ decays. The resulting concentrations of the transients were consistent with an independent factor analysis. It was found that the decay of the radical cations was multiexponential and that the decay varied with pH. A simplified reaction scheme was proposed whereby the absorbing radical cations can alternatively decay by an irreversible channel or react reversibly with OH-. Rate constants for the three elementary reactions of this scheme were determined from an analysis of the decay of the concentration of the radical cations. In addition, the equilibrium constant for the reversible reaction was determined by two separate procedures. In one, the equilibrium constant was calculated from the approximate linear [OH-] dependence of the faster of the two rate constants (in the observed two-exponential decay). The second determination of the equilibrium constant was made from the preexponentials of the empirical two-exponential fits. It was shown how these preexponentials were related to the equilibrium concentrations of the species involved in the equilibrium.