Optical spectroscopy of disorder in molecular chains (J-aggregates)

The form of the exciton absorption band for 1D molecular chains and their l uminescence are investigated in glass matrices of various composition and i n Langmuir-Blodgett (LB) films under selective excitation. It is shown that the exciton absorption band for 1D chains is always asymmetric. The shape of the low-frequency edge of their absorption band changes from the Gaussia n to the Lorentzian depending on the method of obtaining of 1D chains due t o a change in the diagonal and off-diagonal disorder in molecular chains. U nder selective excitation of 1D molecular chains, the effect of considerabl e luminescence band narrowing is not observed. This is associated with stat istical properties of the exciton absorption band and with relaxation proce sses in the materials under investigation in the excited state. (C) 1998 Am erican Institute of Physics. [S1063-777X(98)00712-9].