Anionic as well as cationic species formed through two-photon ionization of dopant chromophores in a copolymer (polyester) film having two weak electron-accepting groups, terephthaloyl and isophthaloyl groups, were simultaneously observed at 20 K by absorption measurement. It is found that most of the photoejected electrons migrate and are localized at higher electron-accepting terephthaloyl groups in the main chain of the polyester. The decay of both ionic species thus formed in the polyester film at low temperatures mainly results from charge recombination. (C) 1997 Elsevier Science B.V.