Abstract
The infrared absorption of polyacetylene doped with high concentrations of potassium has been studied. The samples, doped by a vapor-phase technique to y≈0.08 and y≈0.18, showed doping-induced infrared absorption at ∼900, 1270, and 1390 cm
−1 which was comparable in strength to that seen in [CH(ClO
4)
y
]
χ
with y≈0.06. These experiments were motivated by calculations of the infrared absorption which showed that whereas there are only small differences in the infrared spectra for isolated solitons and isolated polarons there is a dramatic difference between the high-concentration polaron lattice and soliton lattice. The shapes of the absorption spectra are rather similar but the absorption for the polaron lattice is 13 orders of magnitude weaker than that of soliton lattice. The observation of these features at high doping levels appears to be inconsistent with the polaronic metal and strongly disordered Peierls insulator models for highly doped polyacetylene.