Excited-state molecular dynamics simulations of conjugated oligomers usingthe electronic density matrix

Vibrational motions in optically excited polyacetylene and polydiacetylene oligomers are calculated using potential surfaces obtained from the collect ive electronic oscillators (CEO) technique. The role of the effective conju gation coordinate (ECC) in the relaxation processes following an impulsive vertical excitation from the ground state is demonstrated. Real-space analy sis of the electronic transition density matrices shows the charge and bond -order redistribution taking place upon photoexcitation.