The recombination fluorescence from anthracene that has been photoionized at 188 nm in isooctane solutions containing low concentrations of either perfluorocyclobutane (C4F8) or perfluorobenzene (C6F6) has been examined as a function of magnetic-field strength. Level crossing resonances are found at magnetic-field positions predicted by the theory of a hyperfine driven spin evolution on the perfluoroanion (i.e., 0, 452, 757, and 903 G for C4F8 and at 0, 411, and 822 G for C6F6) The widths of the zero-field resonances have been studied as a function of perfluorocarbon concentration. For perfluorocyclobutane, the peak to peak widths of the derivative spectra vary from 6.8 to 13 G over a concentration range from 0.005 to 0.21 M. This variation is quantitatively predicted using the analytic solution to the time-dependent diffusion equation in a Coulomb field to determine how the distribution function for thermalized electron-cation distances evolves into its concentration dependent counterpart for anion-cation separation distances. For perfluorobenzene, the widths are observed to vary over a wider range from 3.0 to 38.5 G for concentrations from 0.0044 to 0.13 M. The additional concentration broadening in this case is consistent with previous estimates of the spin-dephasing rate constant for C6F6-C6F6- charge exchange.