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-aggregates of 1,1'-diethyl-2,2'-quinocyanine bromide (PIC-Br) prepared by a method developed by our group. Difference absorption spectra due to the Kerr effect were induced by changes in a static dipole moment and a polarizability separated by the dual-phase lock-in detection. The change in the static dipole moment associated with the transition from the ground state to the exciton state was measured with an applied ac field (F) of 300 Hz and polarization (e) parallel and perpendicular to the one-dimensional axis (d) of the oriented J-aggregates, and obtained in 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 perpendicular-to d), and 14 (F perpendicular-to d/e perpendicular-to d) D.