Femtosecond Vibrational Dynamics of Self-Trapping in a Quasi-One-Dimensional System

We have directly time resolved the lattice motions associated with the formation of the self-trapped exciton in the quasi-one-dimensional system [Pt(en)₂][Pt(en)₂Br₂] ̇ \.(PF₆)₄ ( en0ex0ex=0ex0exethylene-diamine, C₂H₈N₂), using femtosecond impulsive excitation techniques. A strongly damped, low-frequency wave packet modulation at ~110cm^-1 accompanies the formation of the self-trapped exciton on a ~200fs time scale following excitation of the intervalence charge-transfer transition. Coherent oscillations at the ground state vibrational frequency and its harmonics are also detected.