Analysis of the excited-state absorption spectral bandshape of oligofluorenes
AuthorHayes, Sophia C.
SourceJournal of Chemical Physics
Google Scholar check
MetadataShow full item record
We present ultrafast transient absorption spectra of two oligofluorene derivatives in dilute solution. These spectra display a photoinduced absorption band with clear vibronic structure, which we analyze rigorously using a time-dependent formalism of absorption to extract the principal excited-state vibrational normal-mode frequencies that couple to the electronic transition, the configurational displacement of the higher-lying excited state, and the reorganization energies. We can model the excited-state absorption spectrum using two totally symmetric vibrational modes with frequencies 450 (dimer) or 400 cm-1 (trimer), and 1666 cm-1. The reorganization energy of the ground-state absorption is rather insensitive to the oligomer length at 230 meV. However, that of the excited-state absorption evolves from 58 to 166 meV between the oligofluorene dimer and trimer. Based on previous theoretical work [A. Shukla, Phys. Rev. B 67, 245203 (2003)], we assign the absorption spectra to a transition from the 1 Bu excited state to a higher-lying m A g state, and find that the energy of the excited-state transition with respect to the ground-state transition energy is in excellent agreement with the theoretical predictions for both oligomers studied here. These results and analysis permit profound understanding of the nature of excited-state absorption in π -conjugated polymers, which are the subject of general interest as organic semiconductors in the solid state. © 2010 American Institute of Physics.
Showing items related by title, author, creator and subject.
Othonos, A.; Zervos, Matthew; Tsokkou, D. (2009)We have studied the optical properties and carrier dynamics in SnO 2 nanowires (NWs) with an average radius of 50 nm that were grown via the vapor-liquid solid method. Transient differential absorption measurements have ...
Othonos, Andreas S.; Zervos, Matthew; Tsokkou, Demetra (2009)We have studied the optical properties and carrier dynamics in SnO 2 nanowires (NWs) with an average radius of 50 nm that were grown via the vapor-liquid solid method. Transient differential absorption measurements have ...
Defect states of chemical vapor deposition grown GaN nanowires: Effects and mechanisms in the relaxation of carriers Tsokkou, Demetra; Othonos, Andreas S.; Zervos, Matthew (2009)Carrier relaxation in GaN nanowires, grown by atmospheric pressure chemical vapor deposition, via direct nitridation of Ga with NH3 at 950 °C has been investigated in detail. Differential absorption measurements reveal a ...