Evolution of the total abundances of the negatively charged species with time normalized to the total hydrogen number density (i.e. 2 × 10⁴ cm^-3). We compare the rates from the original WH2008 model that used their selection of k_f electron attachment rates (solid) with the cases: the anthracene rate (long-dashed), the perylene rate (dashed), and the coronene rate (dotted). See text for further details.