self-localized excitations

in conjugated organic polymers
https://doi.org/10.1351/goldbook.ST07417
Physical and chemical properties of conjugated organic polymers with π-electrons have been interpreted in terms of self-localized excitations, which are quasi-particles with structural changes over several repeating units. These excitations can be classified into solitons, polarons, bipolarons and excitons according to their charge and spin.
Source:
PAC, 2007, 79, 293. 'Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)' on page 419 (https://doi.org/10.1351/pac200779030293)