EFFECT OF MAIN-CHAIN LENGTH IN THE EXCITON SPECTRA OF HELICAL-ROD POLYSILANES AS A MODEL OF A 5-ANGSTROM WIDE QUANTUM-WIRE

Helical polysilane rods were regarded as a soluble, polymeric model of a quantum wire with a ∼5 Å width. Spectral characteristics of the lowest exciton band of the helix located at ∼4 eV in isooctane at 20°C were first measured as a function of a wire length varying from ∼35 Å to ∼3000 Å. Both the extinction coefficient and the circular dichroism coefficient were found to tend to increase linearly as the logarithm of the wire length increases, whereas the exciton energy and the spectral band width approached limiting values. © 1994 American Institute of Physics.