Raman Spectra and Electronic Structure of Alkaline Metal Doped Polyacetylene and β-Carotene

Abstract

Abstract Raman spectra of alkaline metal doped polyacetylene were studied at various levels of doping for (CHMy)x, and (CDMy)x, M=Na and K, with y=0–0.18. Several steps in the doping process can be recognized in changes of the Raman spectra; the initial Raman lines remain for y=0–0.06 but change completely into a new pattern at y=0.13. Raman and ESR spectra of alkaline metal doped β-carotene were measured as a model study of the alkaline metal doping of polyacetylene. The correlation of these spectra together with the ab initio SCF MO calculation on model compounds show that a heavily alkaline metal doped polyacetylene chain does not have a uniform bond length structure but is composed of a charged soliton structure connected by a uniform chain. The new Raman bands were assigned based on this structure, implying that a bond alternation still exists in the metallic state of alkaline doped polyacetylene.