QUANTUM DYNAMICS OF INTERACTING EXCITONIC-VIBRONIC DIMER

A carrier on a symmetric dimer with a weak hopping integral, interacti ng (via a site-local coupling) strongly with on-site oscillators is co nsidered. It is shown that the dynamics of the low excited nonstationa ry states is, owing to strong carrier-oscillator correlations, incompa tible with that of the nonlinear Liouville equation theory. The oscill ators are, owing to carrier-oscillator correlations, fully relaxed to the instantaneous rather than to the mean carrier position and need no time-delay or relaxation mechanism to respond to the shifted carrier' s position, in contrast to the usual Holstein and Davydov picture. The origin of the standard Debye-Waller renormalization is scrutinized us ing the Tokuyama-Mori theory including all the excited states of the o scillators and rigorous statements are made concerning its form. Limit ations on the time interval of applicability of the semiclassical desc ription resulting from the carrier dynamics are discussed.