GIANT STATIC DIPOLE-MOMENT CHANGE ON ELECTRONIC EXCITATION IN HIGHLY ORIENTED J-AGGREGATES

A large change in the static dipole moment upon electronic excitation was unexpectedly observed-in highly oriented one-dimensional J-aggrega tes of 1,1'-diethyl-2,2'-quinocyanine bromide (PIC-Br) prepared by a m ethod developed by our group. Difference absorption spectra due to the Kerr effect were induced by changes in a static dipole moment and a p olarizability separated by the dual-phase lock-in detection. The chang e in the static dipole moment associated with the transition from the ground state to the exciton state was measured with an applied ac fiel d (F) of 300 Hz and polarization (e) parallel and perpendicular to the one-dimensional axis (d) of the oriented J-aggregates, and obtained i n each configuration to be 18 (F parallel-to d/e parallel-to d), 12 (F perpendicular-to d/e parallel-to d), 27 (F parallel-to d/e perpendicu lar-to d), and 14 (F perpendicular-to d/e perpendicular-to d) D.