Phonon spectroscopy in pi-conjugated polymers: the role of the excited electronic states

Eitan A. Ehrenfreund; Z. Valy Vardeny

doi:10.1117/12.295532

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1 December 1997 Phonon spectroscopy in π-conjugated polymers: the role of the excited electronic states

Eitan A. Ehrenfreund, Z. Valy Vardeny

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Proceedings Volume 3145, Optical Probes of Conjugated Polymers; (1997) https://doi.org/10.1117/12.295532
Event: Optical Science, Engineering and Instrumentation '97, 1997, San Diego, CA, United States

Abstract

The Raman active vibrational modes in (pi) -conjugated polymers are known to have different frequencies in different types of experiments. The best known examples are the resonant Raman scattering (RRS) and doping or photoinduced absorption infrared active vibrations (IRAV) measurements, in which the same modes appear at different energies. Other examples are the phonon side bands, accompanying the polarons, bipolarons, and solitons absorption bands, in which the same modes give rise to different side band energies. In this work we discuss RRS and IRAV measurements and correlate their experimentally observed frequencies with the relevant electronic state that is active in this type of experiment. We show that the IRAV frequencies are lower than those of RRS since the relevant energy levels of charged solitons and/or polarons are closer to the ground state than the optically allowed 1B_u state of the neutral polymer. Thus a new insight into the meaning of the `pinning' potential, which is associated with the lowest frequency IRAV mode is obtained.

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Eitan A. Ehrenfreund and Z. Valy Vardeny "Phonon spectroscopy in π-conjugated polymers: the role of the excited electronic states", Proc. SPIE 3145, Optical Probes of Conjugated Polymers, (1 December 1997); https://doi.org/10.1117/12.295532

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