Relaxation of the first B u excited state in linear polyenes: From trans-butadiene to polyacetylene
- 1 November 1992
- journal article
- research article
- Published by AIP Publishing in The Journal of Chemical Physics
- Vol. 97 (9), 5970-5976
- https://doi.org/10.1063/1.463734
Abstract
We present a multiphonon approach to analyze the lattice relaxation in the first Bu excited state of linear polyenes, from trans‐butadiene to polyacetylene. Within a single‐electron theory including bond‐length bond‐order relationship, we optimize the geometries of both the ground state and the first excited state and characterize the geometry of the excited state in terms of the formation of soliton–antisoliton pairs (bipolarons). The vibrational modes are simply taken as corresponding to soliton translation and amplitude vibrations (dimerization modes) within the harmonic approximation. Photoabsorption experiments carried out on a series of linear polyenes, β‐carotene, polyenals/polyenones, and polyacetylene are discussed. The Huang–Rhys factor S and the relaxation energy are calculated for polyenes with various lengths. A major result is that we find that the S value first tends to decrease with increasing chain length but after some critical length the evolution completely modifies and S starts increasing. This feature is in good agreement with the experimental data and, in the case of polyacetylene, we are able to reproduce properly the experimental subgap absorption tail. The vibronic behavior for short chains is thus markedly different from that of long chains. We therefore caution that extrapolations based on observations on short polyenes might be invalid for the polymer.Keywords
This publication has 42 references indexed in Scilit:
- Solitons in conducting polymersReviews of Modern Physics, 1988
- Quantum lattice fluctuation and subgap optical absorption intrans-polyacetylenePhysical Review B, 1988
- Synthesis of new conductive polymersSynthetic Metals, 1987
- Spectroscopy of polyenes. 6. Absorption and emission spectral properties of linear polyenals of the series CH3-(CH:CH)n-CHOThe Journal of Physical Chemistry, 1982
- Spectroscopy of polyenes. 5. Absorption and emission spectral properties of polyene acids/esters related to retinoic acid/ester as homologsThe Journal of Physical Chemistry, 1980
- Magnetic susceptibility of doped polyacetylenePhysical Review B, 1979
- Solitons in PolyacetylenePhysical Review Letters, 1979
- Spectroscopy of polyenes. 1. Comprehensive investigation of absorption spectra of polyenals and polyenones related to visual chromophores.The Journal of Physical Chemistry, 1978
- Spectroscopy of polyenes. 2. Comprehensive investigation of emission spectral properties of polyenals and polyenones related to visual chromophoresThe Journal of Physical Chemistry, 1978
- Bond Lengths in Conjugated Molecules: The Present PositionProceedings of the Royal Society of London. Series A - Mathematical and Physical Sciences, 1951