  We investigate localized exciton states in pi-conjugated polymers with finite
torsion. The localized states are associated with a perturbed transfer integral
for which the magnitude of cosine of the torsion angle exceeds the magnitude of
the corresponding cosine of the unperturbed system. The localized state energy
is calculated as a function of the ratio of the perturbed to unperturbed
transfer integrals. Particular attention is paid to the optically active
symmetric localized states, and the effective oscillator strength, or square of
the absolute magnitude of the transition dipole moment, is calculated as a
function of the energy. The relation of the theory to recent optical studies of
poly(di-noctylfluorene)(PF8) is discussed.
