Benzenes in gamma-irradiated low temperature 2-methylpentane matrices with 0, show clear optical absorption attributed to charge resonance bands (CR band) of benzene dimer radical cations (Bz(2)(+)). New absorption bands attributed trimer radical cations (Bz(3)(+)) are also observed with an isobestic point by an increase in the temperature from 82 to 85 K. The derived transition energy of the CR bands by DFT calculation in both Bz(2)(+) and Bz(3)(+) (1.43 and 0.89 eV) is in agreement with the values obtained experimentally (1.41 and 0.90 eV), suggesting that delocalized charge distribution in Bz(3)(+) observed in the present study. (C) 2004 Elsevier B.V. All rights reserved.