Photophysical properties of three radical cations with a pseudo-D-3h electronic structure in acetonitrile were studied by laser flash photolysis and their tandem excitation to their D, state. The theoretical calculations of their electronic levels by the INDO/1 method have indicated that their D-1 and D-0 states deviate from the degenerate state and D-1 <-- D-0 transition has excitation energies of 0.5-1.1 eV with oscillator strengths of nearly zero. The rate constants for their nonradiative decays from the D-2 state increased exponentially with the decrease of the calculated D-2-D-1 energy gap obeying the energy gap law. (C) 2002 Elsevier Science B.V. All rights reserved.