Doubly excited KLL states ofC3+were populated by triple electron capture in collisions of fast bareC6+ions with Ar atoms. Measurements of the Auger electron emission at zero degree with respect to the beam direction were used to determine the absolute single differential cross sections for the triple electron capture to all autoionizing KLL states. In addition, independent particle model was utilized to predict the differential cross section for the population of all doubly excited states of carbon. Theoretical cross sections were critically compared with experimental results. © 2003 American Institute of Physics