Optical absorption spectra and monomer interaction in polymers. Investigation of exciton coupling in DNA hairpins

TL;DR

This paper studies how exciton coupling influences the optical absorption spectra of polymers, especially DNA hairpins, revealing that spectra can reveal monomer interactions despite inhomogeneous broadening.

Contribution

It demonstrates that absorption spectra depend primarily on monomer interactions and are unaffected by inhomogeneous broadening, enabling optical interaction analysis in DNA hairpins.

Findings

Absorption maxima depend on monomer excitation energies and resonant coupling.

Spectra can be used to determine optical interactions between monomers.

Analysis of DNA hairpins reveals exciton localization effects.

Abstract

We investigate the effect of exciton coupling on the optical absorption spectrum of polymer molecules under conditions of strong inhomogeneous broadening. We demonstrate that the dependence of the maximum in the rescaled absorption spectrum on the number of monomers is determined by the average monomer excitation energies and their resonant coupling and insensitive to the inhomogeneous broadening. Thus the absorption spectrum can be used to determine optical interactions between monomers. The results are applied to the absorption spectra of poly-A poly-T DNA hairpins and used to interpret the dependence of the absorption spectrum on the number of monomers. We also discuss exciton localization in these hairpins.