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(abridged) The fairly recent detection of a variety of anions in theInterstellar Molecular Clouds have underlined the importance of realisticallymodeling the processes governing their abundance. To this aim, our earliercalculations for the radiative electron attachment (REA) rates for C4H-, C6H-,and C8H- are employed to generate the corresponding column density ratios ofanion/neutral (A/N) relative abundances. The latter are then compared withthose obtained from observational measurements. The calculations involved thetime-dependent solutions of a large network of chemical processes over anextended time interval and included a series of runs in which the values of REArates were repeatedly scaled. Macroscopic parameters for the clouds' modelingwere also varied to cover a broad range of physical environments. It was foundthat, within the range and quality of the processes included in the presentnetwork,and selected from state-of-the-art astrophysical databases, the REAvalues required to match the observed A/N ratios needed to be reduced by ordersof magnitude for C4H- case, while the same rates for C6H- and C8H- only neededto be scaled by much smaller factors. The results suggest that the generallyproposed formation of interstellar anions by REA mechanism is overestimated bycurrent models for the C4H- case, for which is likely to be an inefficient pathto formation. This path is thus providing a rather marginal contribution to theobserved abundances of C4H-, the latter being more likely to originate fromother chemical processes in the network, as we discuss in some detail in thepresent work.Possible physical reasons for the much smaller differences againstobservations found instead for the values of the (A/N) ratios in two other,longer members of the series are put forward and analyzed within theevolutionary modeling discussed in the present work.

Modeling the role of electron attachment rates on column density ratios for CnH-/CnH (n=4,6,8) in dense molecular clouds