Polymer fluorescence: Even-parity states, alternation, and heteroatoms

Conference · Sat Dec 31 04:00:00 EST 1994

OSTI ID:100963

Soos, Z G ^[1]; Galvao, D S ^[2]; Etemad, S ^[2]

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1. Princeton Univ., NJ (United States). Dept. of Chemistry
2. Bell Communications Research, Red Bank, NJ (United States)

Polymer fluorescence indicates a lowest singlet excitation S{sub 1} of odd parity, while an even-parity S{sub 1} favors radiationless decay. The optical gap E{sub g} defines the lowest odd-parity singlet, 1{sup 1}B{sub u}, and the two-photon gap E{sub a} fixes the 2{sup 1}A{sub g} state. The 1B/2A ordering of conjugated polymers reflects different single-particle gaps, 4t{delta} for alternating chains, at nearly constant correlations. The authors discuss topological and heteroatom contributions to the effective alternation of poly-p-phenylenevinylenes and polythiophenes, respectively, and analyze polymer spectra in term of molecular {pi}-electron theory. Even-parity states at E{sub a} and biexcitons derived from two-electron excitation across E{sub g} indicate intermediate correlations and alternations, thereby limiting the accuracy of band, strong-correlation, and large-{delta} descriptions. Correlated states in the dimer limit illustrate the 2A/1B crossover of Hubbard or excitonic systems.

• OSTI ID: 100963
• Report Number(s): CONF-940142--; ISBN 0-8194-1439-5
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ENERGY GAP
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
FLUORESCENCE
HUBBARD MODEL
ORGANIC POLYMERS
SEMICONDUCTOR MATERIALS