Dynamics of electronic polarization in molecular crystals Original Research Article

Dynamics of electronic polarization in the vicinity of charge carriers in molecular crystals is for the first time investigated here in connection with the carrier transport and intramolecular vibronic polarization. According to standard picture it has been assumed that the electronic polarization relaxation time is extremely short, as estimated from the relation τc = τd1 ≈ h/Eexc, where Eexc is the energy of the first single exciton state. In the case of anthracene (Ac) crystals, the value of τe is about 2 × 10−16 s, i.e. by several orders of magnitude shorter than a typical hopping (residence) time of charge carriers τh = 10−14 -10−13 s. It is argued that typical time of full reconstruction of the electronic polarization after individual carrier hops equals, in the slow carrier regime, approximately to td2 ≈ h/ΔEexc is the width of the lowest singlet-exciton band. In Ac, this means td2 ≈ 0.73 × 10−14 s. Physical implications of this relatively high value of td2 in connection with carrier transport and molecular (vibronic) polarization are discussed.